Why is the sky pink?


On Mars, the sky is pink during the day, shading to blue at sunset. What planet did you think I was talking about?

On Earth, the sky is blue during daytime, turning red at as the sun sinks toward night.

Scattering light

Well, it’s not quite as simple as that: if you ignore your dear sainted mother’s warning and look at the Sun, you’ll see that the sky immediately around the Sun is white, and the sky right at the horizon (if you live in a place where you can get an unobstructed view) is much paler. In between the Sun and the horizon, the sky gradually changes hue, as well as varying through the day. That’s a good clue to help us answer the question every child has asked: why is the sky blue? Or as a Martian child might ask: why is the sky pink?

First of all, light isn’t being absorbed. If you wear a blue shirt, that means the dye in the cotton (or whatever it’s made of) absorbs other colors in light, so only blue is reflected back to your eye. That’s not what’s happening in the air! Instead, light is being bounced off air molecules, a process known as scattering. Air on Earth is about 80% nitrogen, with almost all of the rest being oxygen, so those are the main molecules for us to think about.

As I discussed in my earlier article on fluorescent lights, atoms and molecules can only absorb light of certain colors, based on the laws of quantum mechanics. While oxygen and nitrogen do absorb some of the colors in sunlight, they turn right around and re-emit that light. (I’m oversimplifying slightly, but the main thing is that photons aren’t lost to the world!) However, other colors don’t just pass through atoms as though they aren’t there: they can still interact, and the way we determine how that happens is again the color.

The color of light is determined by its wavelength: how far a wave travels before it repeats itself. Wavelength is also connected to energy: short wavelengths (blue and violet light) have high energy, while long wavelengths (red light) have lower energy. When a photon (a particle of light) hits a nitrogen or oxygen molecule, it might hit one of the electrons inside the molecule. Unless the wavelength is exactly right, the photon doesn’t get absorbed and the electron doesn’t move, so all the photon can do is bounce off, like a pool ball off the rail on a billiards table. Low-energy red photons don’t change direction much after bouncing–they hit the electron too gently for that. Higher-energy blue and violet photons, on the other hand, scatter by quite a bit: they end up moving in a very different direction after hitting an electron than they moving before. This whole process is known technically as Rayleigh scattering, for the physicist John Strutt, Lord Rayleigh.

The blue color of the sky

Not every photon will hit a molecule as it passes through the atmosphere, and light from the Sun contains all the colors mixed together into white light. That means if you look directly at the Sun or the sky right around the Sun during broad daylight, what you see is mostly unscattered light, the photons that pass through the air unmolested, making both Sun and sky look white. (By the way, your body is pretty good at making sure you won’t damage your vision: your reflexes will usually twitch your eyes away before any injury happens. I still don’t recommend looking at the Sun directly for any length of time, especially with sunglasses, which can fool your reflexes into thinking everything is safer than it really is.) In other parts of the sky away from the Sun, scattering is going to be more significant.

The Sun is a long way away, so unlike a light bulb in a house, the light we get from it comes in parallel beams. If you look at a part of the sky away from the Sun, in other words, you’re seeing scattered light! Red light doesn’t get scattered much, so not much of that comes to you, but blue light does, meaning the sky appears blue to our eyes. Bingo! Since there is some green and other colors mixed in as well, the apparent color of the sky is more a blue-white than a pure blue.

(The Sun’s light doesn’t contain as much violet light as it does blue or red, so we won’t see a purple sky. It also helps that our eyes don’t respond strongly to violet light. The cone cells in our retinas are tuned to respond to blue, green, and red, so the other colors are perceived by triggering combinations of the primary cone cells.)

At sunset, light is traveling through a lot more air than it does at noon. That means every ray of light has more of a chance to scatter, removing the blue light before it reaches our eyes. What’s left is red light, making the sky at the horizon near the Sun appear red. In fact, you see more gradations of color too: moving your vision higher in the sky, you’ll note red shades into orange into yellow and so forth, but each color is less intense.

So finally: why is the Martian sky pink? The answer is dust: the surface of Mars is covered in a fine powder, more like talcum than sand. During the frequent windstorms that sweep across the planet, this dust is blown high into the air, where light (yes) scatters off of it. Since the grains are larger than air molecules, the kind of scattering is different, and tends to make the light appear red. (Actually, the sky’s “true” color is very hard to determine, since there is a lot more variation than on Earth.) When there is less dust in the atmosphere, the Martian sky is a deep blue, when the Sun’s light scatters off the carbon dioxide molecules in the air.

By DXS Physics Editor Matthew Francis

Think pink? I’d rather raise a stink

Are some of these possible signs of breast cancer present
in a famous work of art? Image: public domain, US gov
by Liza Gross, contributor
[Ed. note: This article was originally posted on KQED QUEST on October 3, 2012. It is reposted here with kind permission.]
Just a generation ago, October belonged to the colors of fall, when “every green thing loves to die in bright colors,” as Henry Ward Beecher said. (Growing up back East, you read a lot of odes to fall foliage in school.) For years after moving to the Bay Area from Pennsylvania, I felt a twinge of melancholy when October rolled around, knowing the once-demure woodlands would let loose in a fleeting blaze of brash reds and orange-tinged yellows without me.
Now, of course, October belongs to all things pink, as high-profile outfits from the NFL to Ace Hardware set aside 31 days to raise awareness and money for Breast Cancer Awareness Month. (National Breast Cancer Awareness Month was launched in 1985 by CancerCare, a nonprofit cancer support group, and cancer-drug maker AstraZeneca.)
But as women’s health advocate Dr. Susan Love says, awareness of the disease isn’t the issue. “When the NFL is wearing pink gloves, I think you can say we’re aware,” she said last year. “But the awareness isn’t enough.”
Even raising money isn’t enough. You have to ask where that money is going.
It’s a message that gets lost in an ocean of pink-ribbon products (from bagels and teddy bears to vodka and wine glasses), even though critics like the San Francisco-based nonprofit Breast Cancer Action have warned about “pinkwashing” for years, urging people to look behind the feel-good messages to see who’s really benefiting from the commercialization of cancer.
Breast Cancer Action’s Think Before You Pink—Raise a Stink! campaign encourages consumers to think critically about pink products and ask four simple questions to find out what proportion of proceeds go to breast cancer programs and whether the products sold are safe. The group has especially targeted cosmetics companies for marketing pink merchandise even as they sell products with toxic ingredients. (For more information, download the group’s 30-page “toolkit”.)
The group also urges companies to be more transparent and has long called out those it believes use a good cause to increase their bottom line.
Like Eureka, which donated a dollar for every vacuum cleaner sold in its “Clean for the Cure” campaign. Or American Express, which donated a penny per transaction in its “Charge for the Cure.” Both companies bowed out of the pink sweepstakes after Breast Cancer Action asked just how breast cancer patients were benefiting from the campaigns in a 2002 ad in the New York Times.


In October 2000, the San Francisco-based advocacy group 

Breast Cancer Action ran a full page ad in the New York Times 
West Coast Edition with text (not shown) inviting readers to 
participate in its ”Stop Cancer Where It Starts” Campaign. 
The campaign criticized breast cancer awareness campaigns 
for pushing early detection and mammograms 
(without acknowledging their limitations) while ignoring prevention. 
(Image: Courtesy Breast Cancer Action)

Others, like KFC with its 2010 “Buckets for the Cure” campaign, climb on the pink bandwagon to peddle decidedly unhealthy products. Stephen Colbert’s take on the “pink bucket dilemma” shows just how ludicrous cause marketing has become. (Forward to 1:13.)

But even when money goes to breast cancer programs and not corporate coffers, is it going to the right place? Love (and several advocacy groups) has said for years that we need to shift our focus from cures to causes—and prevention.
If we can develop a vaccine for cervical cancer, says Love, why not for breast cancer? Early results of a clinical trial show promising results for a vaccine designed to prevent recurrence of one form of breast cancer. (The data were presented at a meeting and have not yet gone through peer review.)
As I wrote in May, Love’s Research Foundation is looking for volunteers in her online Army of Women to identify potential causes in order to eradicate the disease. (Anyone can sign up.)


In the late 1990s, The Breast Cancer Fund, the American Cancer Society, 

and the Susan G. Komen Breast Cancer Foundation invited American 
artists and writers to submit work about their breast cancer experiences. 
The resulting exhibit (and book)—Art.Rage.Us.—opened in 1998 
at San Francisco’s Main Library. At the time, project coordinator and 
Breast Cancer Action Co-founder Susan Claymon said, 
“Art.Rage.Us. presents deeply moving and beautiful expressions 
from women with breast cancer, along with intensely personal 
statements that provide a window into their hearts and minds.” 
Claymon died of breast cancer in 2000. She was 61.

Prevention is also a primary concern for the Athena Breast Health Network, a partnership of the five University of California medical centers that collects personalized data on breast cancer patients to optimize treatment and ultimately figure out how to stop cancer before it starts. The site also includes a comprehensive list of breast cancer risk factors.

Recent research suggests that the biology behind one of the listed risk factors, dense breast tissue, may be more complicated than previously thought. Earlier studies found that women with dense breasts had a higher risk of developing breast cancer. (And this finding led to the“right to know” legislation that Gov. Brown recently signed, requiring doctors to tell women if their mammograms show they have dense breasts.) But a recent study in the Journal of the National Cancer Institute suggests that women with denser breasts are not more likely to die of breast cancer. The greatest risk was found for women who had the fattiest breast tissue, a condition linked to obesity. This suggests that if you have dense breast tissue, you may be more likely to get cancer—but not die of it. Love’s blog explained the significance of the findings:
The recent study on breast density showed us, yet again, that women who are obese when they are diagnosed with breast cancer are more likely to die of breast cancer than women who are not obese. Doctors need to do more than tell women about their breast density or remind them to get a mammogram. They need to be teaching women the importance of exercising, losing weight (if necessary) and eating a well-balanced diet—both before and after a breast cancer diagnosis. Continue reading

We gotta watch out for feminine role models wearing pink

Beware blonde, feminine role models wearing pink.
(Source)

Today’s guest post comes to us courtesy of Sara Callori. She is a physics Ph.D. candidate at Stony Brook University in Long Island, NY. In the lab, Sara loves working with x-rays and even has a Bragg diffraction tattoo. She would eventually like to focus on science teaching and outreach because she loves to get people to stop being intimidated when they think of physics.
This may sound odd, but I never aspired to be feminine until I became a physicist. I grew up playing sports and getting short haircuts. There were phases when my mother would have had to tranquilize me to get me into a dress (this was infrequent as my tom-boy qualities seemed to come from her own lack of femininity). As I got older, I started to develop some style, but it was more comfort over fashion, especially when it came down to 8 am classes in undergrad. When I made the decision to go into graduate school for physics, however, my outlook changed. I wanted to be someone who bucked the stereotype: a fashionable, fun, young woman who also is a successful physicist. I thought that if I didn’t look like the stereotypical physicist, I could be someone that was a role model to younger students by demonstrating an alternative to the stereotype of who can be a scientist.
This week researchers at the University of Michigan released findings that dashed my hopes for being the cool physicist that younger girls want to emulate. In a paper titled “My Fair Physicist? Feminine Math and Science Role Models Demotivate Young Girls”, psychology researchers Diana Betz and Denise Sekaquaptewa found that women presented as both successful in science/technology/engineering/math (STEM) careers and possessing “feminine traits” negatively affected how young girls viewed science and math.
When I read the summary of these findings, I was dismayed. I became even more disappointed when I read that for feminine traits they used “wearing make-up and pink clothes, liking fashion magazines”. Gender-neutral women were given traits such as “wearing dark-colored clothes and glasses, likes reading”.
The assignment of these traits bothered me on several levels. The most immediate was how narrow the study’s concept of “feminine” seemed. If you asked me if I considered myself feminine, I would say yes. I like colorful dresses during the summer and own too many purses — but I also wear glasses, play rugby, and have tattoos. Most real-life women, including women in STEM, also possess traits from a mix of “feminine” and “gender-neutral” categories. It is important to remember these are the women younger students will encounter when they are introduced to female scientists.  
Additionally, the researchers’ idea of “feminine” seems to play into another set of negative stereotypes common in popular culture, what you might call the “Legally Blonde” scenario. In the movie, the protagonist is a woman who could easily be described as “wearing make-up and pink clothes, liking fashion magazines”. The story builds around how someone with those traits is perceived as unintelligent and unsuited for work that requires a strong academic background. While throughout the story, the main character shows she isn’t just a pretty face, there are still many people who will associate these types of feminine traits with unintelligence. 
This association is at odds with women in STEM fields and it makes me wonder if some of the girls’ negative associations of feminine STEM professionals were due to those traits being perceived as incompatible with women in STEM careers. (To briefly address the finding which showed that femininity could be compatible with overall school success, the “success” descriptions seem to be generic enough that they could be interpreted as encompassing non-academic accomplishments as well; e.g. being well liked by classmates or elected to the student council.)
This study also unsettled me on a personal level. I’ve long desired to be a role model to younger students. I enjoy sharing the excitement of physics, especially with those who might be turned away from the subject because of stereotypes or negative perceptions. I always thought that by being outgoing, fun, and yes, feminine would enable me to reach students who see physics as the domain of old white men. These results have me questioning myself, which can only hurt my outreach efforts by making me more self conscious about them. They make me wonder if I have to be disingenuous about who I am in order to avoid being seen as “too feminine” for physics.
Overall, that this study could be useful as a springboard for improving discussion and ideas for motivating girls in STEM. However, I think that their idea of “feminine” is too narrow to apply these findings broadly. Rather than work in the black and white “feminine” vs. “gender neutral” cases, why not build further ideas, research, and programs around much more realistic types of women who are currently succeeding in many STEM fields.
These views are the opinion of the author and do not necessarily either reflect or disagree with those of the
DXS editorial team. 

Biology Explainer: The big 4 building blocks of life–carbohydrates, fats, proteins, and nucleic acids

The short version
  • The four basic categories of molecules for building life are carbohydrates, lipids, proteins, and nucleic acids.
  • Carbohydrates serve many purposes, from energy to structure to chemical communication, as monomers or polymers.
  • Lipids, which are hydrophobic, also have different purposes, including energy storage, structure, and signaling.
  • Proteins, made of amino acids in up to four structural levels, are involved in just about every process of life.                                                                                                      
  • The nucleic acids DNA and RNA consist of four nucleotide building blocks, and each has different purposes.
The longer version
Life is so diverse and unwieldy, it may surprise you to learn that we can break it down into four basic categories of molecules. Possibly even more implausible is the fact that two of these categories of large molecules themselves break down into a surprisingly small number of building blocks. The proteins that make up all of the living things on this planet and ensure their appropriate structure and smooth function consist of only 20 different kinds of building blocks. Nucleic acids, specifically DNA, are even more basic: only four different kinds of molecules provide the materials to build the countless different genetic codes that translate into all the different walking, swimming, crawling, oozing, and/or photosynthesizing organisms that populate the third rock from the Sun.

                                                  

Big Molecules with Small Building Blocks

The functional groups, assembled into building blocks on backbones of carbon atoms, can be bonded together to yield large molecules that we classify into four basic categories. These molecules, in many different permutations, are the basis for the diversity that we see among living things. They can consist of thousands of atoms, but only a handful of different kinds of atoms form them. It’s like building apartment buildings using a small selection of different materials: bricks, mortar, iron, glass, and wood. Arranged in different ways, these few materials can yield a huge variety of structures.

We encountered functional groups and the SPHONC in Chapter 3. These components form the four categories of molecules of life. These Big Four biological molecules are carbohydrates, lipids, proteins, and nucleic acids. They can have many roles, from giving an organism structure to being involved in one of the millions of processes of living. Let’s meet each category individually and discover the basic roles of each in the structure and function of life.
Carbohydrates

You have met carbohydrates before, whether you know it or not. We refer to them casually as “sugars,” molecules made of carbon, hydrogen, and oxygen. A sugar molecule has a carbon backbone, usually five or six carbons in the ones we’ll discuss here, but it can be as few as three. Sugar molecules can link together in pairs or in chains or branching “trees,” either for structure or energy storage.

When you look on a nutrition label, you’ll see reference to “sugars.” That term includes carbohydrates that provide energy, which we get from breaking the chemical bonds in a sugar called glucose. The “sugars” on a nutrition label also include those that give structure to a plant, which we call fiber. Both are important nutrients for people.

Sugars serve many purposes. They give crunch to the cell walls of a plant or the exoskeleton of a beetle and chemical energy to the marathon runner. When attached to other molecules, like proteins or fats, they aid in communication between cells. But before we get any further into their uses, let’s talk structure.

The sugars we encounter most in basic biology have their five or six carbons linked together in a ring. There’s no need to dive deep into organic chemistry, but there are a couple of essential things to know to interpret the standard representations of these molecules.

Check out the sugars depicted in the figure. The top-left molecule, glucose, has six carbons, which have been numbered. The sugar to its right is the same glucose, with all but one “C” removed. The other five carbons are still there but are inferred using the conventions of organic chemistry: Anywhere there is a corner, there’s a carbon unless otherwise indicated. It might be a good exercise for you to add in a “C” over each corner so that you gain a good understanding of this convention. You should end up adding in five carbon symbols; the sixth is already given because that is conventionally included when it occurs outside of the ring.

On the left is a glucose with all of its carbons indicated. They’re also numbered, which is important to understand now for information that comes later. On the right is the same molecule, glucose, without the carbons indicated (except for the sixth one). Wherever there is a corner, there is a carbon, unless otherwise indicated (as with the oxygen). On the bottom left is ribose, the sugar found in RNA. The sugar on the bottom right is deoxyribose. Note that at carbon 2 (*), the ribose and deoxyribose differ by a single oxygen.

The lower left sugar in the figure is a ribose. In this depiction, the carbons, except the one outside of the ring, have not been drawn in, and they are not numbered. This is the standard way sugars are presented in texts. Can you tell how many carbons there are in this sugar? Count the corners and don’t forget the one that’s already indicated!

If you said “five,” you are right. Ribose is a pentose (pent = five) and happens to be the sugar present in ribonucleic acid, or RNA. Think to yourself what the sugar might be in deoxyribonucleic acid, or DNA. If you thought, deoxyribose, you’d be right.

The fourth sugar given in the figure is a deoxyribose. In organic chemistry, it’s not enough to know that corners indicate carbons. Each carbon also has a specific number, which becomes important in discussions of nucleic acids. Luckily, we get to keep our carbon counting pretty simple in basic biology. To count carbons, you start with the carbon to the right of the non-carbon corner of the molecule. The deoxyribose or ribose always looks to me like a little cupcake with a cherry on top. The “cherry” is an oxygen. To the right of that oxygen, we start counting carbons, so that corner to the right of the “cherry” is the first carbon. Now, keep counting. Here’s a little test: What is hanging down from carbon 2 of the deoxyribose?

If you said a hydrogen (H), you are right! Now, compare the deoxyribose to the ribose. Do you see the difference in what hangs off of the carbon 2 of each sugar? You’ll see that the carbon 2 of ribose has an –OH, rather than an H. The reason the deoxyribose is called that is because the O on the second carbon of the ribose has been removed, leaving a “deoxyed” ribose. This tiny distinction between the sugars used in DNA and RNA is significant enough in biology that we use it to distinguish the two nucleic acids.

In fact, these subtle differences in sugars mean big differences for many biological molecules. Below, you’ll find a couple of ways that apparently small changes in a sugar molecule can mean big changes in what it does. These little changes make the difference between a delicious sugar cookie and the crunchy exoskeleton of a dung beetle.

Sugar and Fuel

A marathon runner keeps fuel on hand in the form of “carbs,” or sugars. These fuels provide the marathoner’s straining body with the energy it needs to keep the muscles pumping. When we take in sugar like this, it often comes in the form of glucose molecules attached together in a polymer called starch. We are especially equipped to start breaking off individual glucose molecules the minute we start chewing on a starch.

Double X Extra: A monomer is a building block (mono = one) and a polymer is a chain of monomers. With a few dozen monomers or building blocks, we get millions of different polymers. That may sound nutty until you think of the infinity of values that can be built using only the numbers 0 through 9 as building blocks or the intricate programming that is done using only a binary code of zeros and ones in different combinations.

Our bodies then can rapidly take the single molecules, or monomers, into cells and crack open the chemical bonds to transform the energy for use. The bonds of a sugar are packed with chemical energy that we capture to build a different kind of energy-containing molecule that our muscles access easily. Most species rely on this process of capturing energy from sugars and transforming it for specific purposes.

Polysaccharides: Fuel and Form

Plants use the Sun’s energy to make their own glucose, and starch is actually a plant’s way of storing up that sugar. Potatoes, for example, are quite good at packing away tons of glucose molecules and are known to dieticians as a “starchy” vegetable. The glucose molecules in starch are packed fairly closely together. A string of sugar molecules bonded together through dehydration synthesis, as they are in starch, is a polymer called a polysaccharide (poly = many; saccharide = sugar). When the monomers of the polysaccharide are released, as when our bodies break them up, the reaction that releases them is called hydrolysis.

Double X Extra: The specific reaction that hooks one monomer to another in a covalent bond is called dehydration synthesis because in making the bond–synthesizing the larger molecule–a molecule of water is removed (dehydration). The reverse is hydrolysis (hydro = water; lysis = breaking), which breaks the covalent bond by the addition of a molecule of water.

Although plants make their own glucose and animals acquire it by eating the plants, animals can also package away the glucose they eat for later use. Animals, including humans, store glucose in a polysaccharide called glycogen, which is more branched than starch. In us, we build this energy reserve primarily in the liver and access it when our glucose levels drop.

Whether starch or glycogen, the glucose molecules that are stored are bonded together so that all of the molecules are oriented the same way. If you view the sixth carbon of the glucose to be a “carbon flag,” you’ll see in the figure that all of the glucose molecules in starch are oriented with their carbon flags on the upper left.

The orientation of monomers of glucose in polysaccharides can make a big difference in the use of the polymer. The glucoses in the molecule on the top are all oriented “up” and form starch. The glucoses in the molecule on the bottom alternate orientation to form cellulose, which is quite different in its function from starch.

Storing up sugars for fuel and using them as fuel isn’t the end of the uses of sugar. In fact, sugars serve as structural molecules in a huge variety of organisms, including fungi, bacteria, plants, and insects.

The primary structural role of a sugar is as a component of the cell wall, giving the organism support against gravity. In plants, the familiar old glucose molecule serves as one building block of the plant cell wall, but with a catch: The molecules are oriented in an alternating up-down fashion. The resulting structural sugar is called cellulose.

That simple difference in orientation means the difference between a polysaccharide as fuel for us and a polysaccharide as structure. Insects take it step further with the polysaccharide that makes up their exoskeleton, or outer shell. Once again, the building block is glucose, arranged as it is in cellulose, in an alternating conformation. But in insects, each glucose has a little extra added on, a chemical group called an N-acetyl group. This addition of a single functional group alters the use of cellulose and turns it into a structural molecule that gives bugs that special crunchy sound when you accidentally…ahem…step on them.

These variations on the simple theme of a basic carbon-ring-as-building-block occur again and again in biological systems. In addition to serving roles in structure and as fuel, sugars also play a role in function. The attachment of subtly different sugar molecules to a protein or a lipid is one way cells communicate chemically with one another in refined, regulated interactions. It’s as though the cells talk with each other using a specialized, sugar-based vocabulary. Typically, cells display these sugary messages to the outside world, making them available to other cells that can recognize the molecular language.

Lipids: The Fatty Trifecta

Starch makes for good, accessible fuel, something that we immediately attack chemically and break up for quick energy. But fats are energy that we are supposed to bank away for a good long time and break out in times of deprivation. Like sugars, fats serve several purposes, including as a dense source of energy and as a universal structural component of cell membranes everywhere.

Fats: the Good, the Bad, the Neutral

Turn again to a nutrition label, and you’ll see a few references to fats, also known as lipids. (Fats are slightly less confusing that sugars in that they have only two names.) The label may break down fats into categories, including trans fats, saturated fats, unsaturated fats, and cholesterol. You may have learned that trans fats are “bad” and that there is good cholesterol and bad cholesterol, but what does it all mean?

Let’s start with what we mean when we say saturated fat. The question is, saturated with what? There is a specific kind of dietary fat call the triglyceride. As its name implies, it has a structural motif in which something is repeated three times. That something is a chain of carbons and hydrogens, hanging off in triplicate from a head made of glycerol, as the figure shows.  Those three carbon-hydrogen chains, or fatty acids, are the “tri” in a triglyceride. Chains like this can be many carbons long.

Double X Extra: We call a fatty acid a fatty acid because it’s got a carboxylic acid attached to a fatty tail. A triglyceride consists of three of these fatty acids attached to a molecule called glycerol. Our dietary fat primarily consists of these triglycerides.

Triglycerides come in several forms. You may recall that carbon can form several different kinds of bonds, including single bonds, as with hydrogen, and double bonds, as with itself. A chain of carbon and hydrogens can have every single available carbon bond taken by a hydrogen in single covalent bond. This scenario of hydrogen saturation yields a saturated fat. The fat is saturated to its fullest with every covalent bond taken by hydrogens single bonded to the carbons.

Saturated fats have predictable characteristics. They lie flat easily and stick to each other, meaning that at room temperature, they form a dense solid. You will realize this if you find a little bit of fat on you to pinch. Does it feel pretty solid? That’s because animal fat is saturated fat. The fat on a steak is also solid at room temperature, and in fact, it takes a pretty high heat to loosen it up enough to become liquid. Animals are not the only organisms that produce saturated fat–avocados and coconuts also are known for their saturated fat content.

The top graphic above depicts a triglyceride with the glycerol, acid, and three hydrocarbon tails. The tails of this saturated fat, with every possible hydrogen space occupied, lie comparatively flat on one another, and this kind of fat is solid at room temperature. The fat on the bottom, however, is unsaturated, with bends or kinks wherever two carbons have double bonded, booting a couple of hydrogens and making this fat unsaturated, or lacking some hydrogens. Because of the space between the bumps, this fat is probably not solid at room temperature, but liquid.

You can probably now guess what an unsaturated fat is–one that has one or more hydrogens missing. Instead of single bonding with hydrogens at every available space, two or more carbons in an unsaturated fat chain will form a double bond with carbon, leaving no space for a hydrogen. Because some carbons in the chain share two pairs of electrons, they physically draw closer to one another than they do in a single bond. This tighter bonding result in a “kink” in the fatty acid chain.

In a fat with these kinks, the three fatty acids don’t lie as densely packed with each other as they do in a saturated fat. The kinks leave spaces between them. Thus, unsaturated fats are less dense than saturated fats and often will be liquid at room temperature. A good example of a liquid unsaturated fat at room temperature is canola oil.

A few decades ago, food scientists discovered that unsaturated fats could be resaturated or hydrogenated to behave more like saturated fats and have a longer shelf life. The process of hydrogenation–adding in hydrogens–yields trans fat. This kind of processed fat is now frowned upon and is being removed from many foods because of its associations with adverse health effects. If you check a food label and it lists among the ingredients “partially hydrogenated” oils, that can mean that the food contains trans fat.

Double X Extra: A triglyceride can have up to three different fatty acids attached to it. Canola oil, for example, consists primarily of oleic acid, linoleic acid, and linolenic acid, all of which are unsaturated fatty acids with 18 carbons in their chains.

Why do we take in fat anyway? Fat is a necessary nutrient for everything from our nervous systems to our circulatory health. It also, under appropriate conditions, is an excellent way to store up densely packaged energy for the times when stores are running low. We really can’t live very well without it.

Phospholipids: An Abundant Fat

You may have heard that oil and water don’t mix, and indeed, it is something you can observe for yourself. Drop a pat of butter–pure saturated fat–into a bowl of water and watch it just sit there. Even if you try mixing it with a spoon, it will just sit there. Now, drop a spoon of salt into the water and stir it a bit. The salt seems to vanish. You’ve just illustrated the difference between a water-fearing (hydrophobic) and a water-loving (hydrophilic) substance.

Generally speaking, compounds that have an unequal sharing of electrons (like ions or anything with a covalent bond between oxygen and hydrogen or nitrogen and hydrogen) will be hydrophilic. The reason is that a charge or an unequal electron sharing gives the molecule polarity that allows it to interact with water through hydrogen bonds. A fat, however, consists largely of hydrogen and carbon in those long chains. Carbon and hydrogen have roughly equivalent electronegativities, and their electron-sharing relationship is relatively nonpolar. Fat, lacking in polarity, doesn’t interact with water. As the butter demonstrated, it just sits there.

There is one exception to that little maxim about fat and water, and that exception is the phospholipid. This lipid has a special structure that makes it just right for the job it does: forming the membranes of cells. A phospholipid consists of a polar phosphate head–P and O don’t share equally–and a couple of nonpolar hydrocarbon tails, as the figure shows. If you look at the figure, you’ll see that one of the two tails has a little kick in it, thanks to a double bond between the two carbons there.

Phospholipids form a double layer and are the major structural components of cell membranes. Their bend, or kick, in one of the hydrocarbon tails helps ensure fluidity of the cell membrane. The molecules are bipolar, with hydrophilic heads for interacting with the internal and external watery environments of the cell and hydrophobic tails that help cell membranes behave as general security guards.

The kick and the bipolar (hydrophobic and hydrophilic) nature of the phospholipid make it the perfect molecule for building a cell membrane. A cell needs a watery outside to survive. It also needs a watery inside to survive. Thus, it must face the inside and outside worlds with something that interacts well with water. But it also must protect itself against unwanted intruders, providing a barrier that keeps unwanted things out and keeps necessary molecules in.

Phospholipids achieve it all. They assemble into a double layer around a cell but orient to allow interaction with the watery external and internal environments. On the layer facing the inside of the cell, the phospholipids orient their polar, hydrophilic heads to the watery inner environment and their tails away from it. On the layer to the outside of the cell, they do the same.
As the figure shows, the result is a double layer of phospholipids with each layer facing a polar, hydrophilic head to the watery environments. The tails of each layer face one another. They form a hydrophobic, fatty moat around a cell that serves as a general gatekeeper, much in the way that your skin does for you. Charged particles cannot simply slip across this fatty moat because they can’t interact with it. And to keep the fat fluid, one tail of each phospholipid has that little kick, giving the cell membrane a fluid, liquidy flow and keeping it from being solid and unforgiving at temperatures in which cells thrive.

Steroids: Here to Pump You Up?

Our final molecule in the lipid fatty trifecta is cholesterol. As you may have heard, there are a few different kinds of cholesterol, some of which we consider to be “good” and some of which is “bad.” The good cholesterol, high-density lipoprotein, or HDL, in part helps us out because it removes the bad cholesterol, low-density lipoprotein or LDL, from our blood. The presence of LDL is associated with inflammation of the lining of the blood vessels, which can lead to a variety of health problems.

But cholesterol has some other reasons for existing. One of its roles is in the maintenance of cell membrane fluidity. Cholesterol is inserted throughout the lipid bilayer and serves as a block to the fatty tails that might otherwise stick together and become a bit too solid.

Cholesterol’s other starring role as a lipid is as the starting molecule for a class of hormones we called steroids or steroid hormones. With a few snips here and additions there, cholesterol can be changed into the steroid hormones progesterone, testosterone, or estrogen. These molecules look quite similar, but they play very different roles in organisms. Testosterone, for example, generally masculinizes vertebrates (animals with backbones), while progesterone and estrogen play a role in regulating the ovulatory cycle.

Double X Extra: A hormone is a blood-borne signaling molecule. It can be lipid based, like testosterone, or short protein, like insulin.

Proteins

As you progress through learning biology, one thing will become more and more clear: Most cells function primarily as protein factories. It may surprise you to learn that proteins, which we often talk about in terms of food intake, are the fundamental molecule of many of life’s processes. Enzymes, for example, form a single broad category of proteins, but there are millions of them, each one governing a small step in the molecular pathways that are required for living.

Levels of Structure

Amino acids are the building blocks of proteins. A few amino acids strung together is called a peptide, while many many peptides linked together form a polypeptide. When many amino acids strung together interact with each other to form a properly folded molecule, we call that molecule a protein.

For a string of amino acids to ultimately fold up into an active protein, they must first be assembled in the correct order. The code for their assembly lies in the DNA, but once that code has been read and the amino acid chain built, we call that simple, unfolded chain the primary structure of the protein.

This chain can consist of hundreds of amino acids that interact all along the sequence. Some amino acids are hydrophobic and some are hydrophilic. In this context, like interacts best with like, so the hydrophobic amino acids will interact with one another, and the hydrophilic amino acids will interact together. As these contacts occur along the string of molecules, different conformations will arise in different parts of the chain. We call these different conformations along the amino acid chain the protein’s secondary structure.

Once those interactions have occurred, the protein can fold into its final, or tertiary structure and be ready to serve as an active participant in cellular processes. To achieve the tertiary structure, the amino acid chain’s secondary interactions must usually be ongoing, and the pH, temperature, and salt balance must be just right to facilitate the folding. This tertiary folding takes place through interactions of the secondary structures along the different parts of the amino acid chain.

The final product is a properly folded protein. If we could see it with the naked eye, it might look a lot like a wadded up string of pearls, but that “wadded up” look is misleading. Protein folding is a carefully regulated process that is determined at its core by the amino acids in the chain: their hydrophobicity and hydrophilicity and how they interact together.

In many instances, however, a complete protein consists of more than one amino acid chain, and the complete protein has two or more interacting strings of amino acids. A good example is hemoglobin in red blood cells. Its job is to grab oxygen and deliver it to the body’s tissues. A complete hemoglobin protein consists of four separate amino acid chains all properly folded into their tertiary structures and interacting as a single unit. In cases like this involving two or more interacting amino acid chains, we say that the final protein has a quaternary structure. Some proteins can consist of as many as a dozen interacting chains, behaving as a single protein unit.

A Plethora of Purposes

What does a protein do? Let us count the ways. Really, that’s almost impossible because proteins do just about everything. Some of them tag things. Some of them destroy things. Some of them protect. Some mark cells as “self.” Some serve as structural materials, while others are highways or motors. They aid in communication, they operate as signaling molecules, they transfer molecules and cut them up, they interact with each other in complex, interrelated pathways to build things up and break things down. They regulate genes and package DNA, and they regulate and package each other.

As described above, proteins are the final folded arrangement of a string of amino acids. One way we obtain these building blocks for the millions of proteins our bodies make is through our diet. You may hear about foods that are high in protein or people eating high-protein diets to build muscle. When we take in those proteins, we can break them apart and use the amino acids that make them up to build proteins of our own.

Nucleic Acids

How does a cell know which proteins to make? It has a code for building them, one that is especially guarded in a cellular vault in our cells called the nucleus. This code is deoxyribonucleic acid, or DNA. The cell makes a copy of this code and send it out to specialized structures that read it and build proteins based on what they read. As with any code, a typo–a mutation–can result in a message that doesn’t make as much sense. When the code gets changed, sometimes, the protein that the cell builds using that code will be changed, too.

Biohazard!The names associated with nucleic acids can be confusing because they all start with nucle-. It may seem obvious or easy now, but a brain freeze on a test could mix you up. You need to fix in your mind that the shorter term (10 letters, four syllables), nucleotide, refers to the smaller molecule, the three-part building block. The longer term (12 characters, including the space, and five syllables), nucleic acid, which is inherent in the names DNA and RNA, designates the big, long molecule.

DNA vs. RNA: A Matter of Structure

DNA and its nucleic acid cousin, ribonucleic acid, or RNA, are both made of the same kinds of building blocks. These building blocks are called nucleotides. Each nucleotide consists of three parts: a sugar (ribose for RNA and deoxyribose for DNA), a phosphate, and a nitrogenous base. In DNA, every nucleotide has identical sugars and phosphates, and in RNA, the sugar and phosphate are also the same for every nucleotide.

So what’s different? The nitrogenous bases. DNA has a set of four to use as its coding alphabet. These are the purines, adenine and guanine, and the pyrimidines, thymine and cytosine. The nucleotides are abbreviated by their initial letters as A, G, T, and C. From variations in the arrangement and number of these four molecules, all of the diversity of life arises. Just four different types of the nucleotide building blocks, and we have you, bacteria, wombats, and blue whales.

RNA is also basic at its core, consisting of only four different nucleotides. In fact, it uses three of the same nitrogenous bases as DNA–A, G, and C–but it substitutes a base called uracil (U) where DNA uses thymine. Uracil is a pyrimidine.

DNA vs. RNA: Function Wars

An interesting thing about the nitrogenous bases of the nucleotides is that they pair with each other, using hydrogen bonds, in a predictable way. An adenine will almost always bond with a thymine in DNA or a uracil in RNA, and cytosine and guanine will almost always bond with each other. This pairing capacity allows the cell to use a sequence of DNA and build either a new DNA sequence, using the old one as a template, or build an RNA sequence to make a copy of the DNA.

These two different uses of A-T/U and C-G base pairing serve two different purposes. DNA is copied into DNA usually when a cell is preparing to divide and needs two complete sets of DNA for the new cells. DNA is copied into RNA when the cell needs to send the code out of the vault so proteins can be built. The DNA stays safely where it belongs.

RNA is really a nucleic acid jack-of-all-trades. It not only serves as the copy of the DNA but also is the main component of the two types of cellular workers that read that copy and build proteins from it. At one point in this process, the three types of RNA come together in protein assembly to make sure the job is done right.


 By Emily Willingham, DXS managing editor 
This material originally appeared in similar form in Emily Willingham’s Complete Idiot’s Guide to College Biology

LEGO those gender stereotypes


My daughter, patiently waiting to get her own balloon jetpack.
Photo credit: Phil Blake
Why can’t you understand that my daughter wants a damn jetpack?

Last weekend, I took my daughters to a birthday party that featured a magician/balloon artist.  He was really fantastic with the kids, and kept their attention for close to 1 hour (ONE HOUR!!!).  At the end of his magic show, he began to furiously twist and tie balloons into these amazing shapes, promoting energetic and imaginative play.  Of these shapes was his own, very intricate invention: a jetpack.  

When he completed the first jetpack, I watched as the eyes of my five-year-old daughter, who happens to be a very sporty kid, light up with wonder.  She looked at me and smiled, indicating through her facial expression alone that she wanted the same balloon toy.  But, alas, when it was her turn for a balloon, her requests were met with opposition.  Here was the conversation:

Magician: How about a great butterfly balloon?

Daughter: No thanks, I’d like a jetpack please.

Magician: I think you should get a butterfly.

Daughter: I’d prefer a jetpack.

Magician: But you’re a girl.  Girls get butterflies.

Daughter (giving me a desperate look): But I really want a jetpack!

Realizing that my daughter was becoming unnecessarily upset, especially given the fact that there were 3 boys already engaging in play with their totally awesome jetpacks, myself and the hostess mother intervened.  We kindly reiterated my daughter’s requests for a jetpack.  And, so she was given a jetpack.

Later that evening, my daughter asked me why the magician insisted that she get a butterfly balloon when she explicitly asked for a jetpack.  Not wanting to reveal the realities of gender stereotype at that very point in time, I simply stated that sometimes we (a gender neutral “we”) might have to repeat ourselves so that others understand what we want.  Then she asked, “but why are butterflies only for girls?”

I was able to more or less able smooth it over with her, but it was clear to me that a very archaic reality was still in play, and my daughters were about to inherit it.  While I have nothing against typically female role-playing or dolls or princesses, I do not like when they are assumed to be the preferred activities.  I also do not like the idea that some toys, based on years of “market research,” are designed to basically pigeonhole girls into a June Cleaveresque state of being, especially without alternative play options.

The five LEGO Friends 
For instance, LEGO has recently launched a “for-girls-only” campaign, exemplified by the new “Friends” LEGO kit.  Slathered in pink and purple, this kit is designed around a narrative involving five friends and a pretend city named Heartlake.  Like nearly all cities, Heartlake boasts a bakery, a beauty salon, a cafe, and a veterinarian’s office to take care of sick animals.  However, unlike every city, Heartlake lacks things like a hospital, a fire department, a police station, and a local airport (thought they do have a flying club).  In essence, this toy is facilitating pretend play that centers ONLY on domestication, which absolutely limits both experiences and expectations for girls playing with this toy.  In essence, LEGO is assuming that all girls want the butterfly balloon instead of the jetpack.

Some might think, “jeeze, it’s just a toy!” and dismiss my objection to all that the Friends kit encompasses.  And perhaps when the Friends kit is offered in addition to a variety of toy types – gender neutral, masculine, and feminine – it may not have a significant effect on the mindset of its young, impressionable owner.  But what if that’s not the case?

Traditional LEGO bricks: For boys AND girls, goshdarnit!
LEGO has also gotten it wrong when it comes to the assumption that girls are not into the traditional LEGO blocks.  In fact, just last night, my daughter (the very one who wanted a jetpack) saw a commercial for a LEGO City product – I forgot which one – and asked that we put it on her ever expanding Christmas list.  Furthermore, both of my daughters are huge fans of the LEGO produced show on the Cartoon Network, Ninjago: Masters of Spinjitzu, which is based on the traditional LEGO figures and game.  My oldest daughter is arguably very sporty and may be more inclined to like “boy” things, but my younger daughter is chock-full of sugar and spice and yada yada yada.  She prefers to wear dresses, LOVES shoes, and demands to have her nails painted at all times.  And she still gets down with regular LEGOs and monster trucks and basketball and karate (all her own choices).  So why is LEGO shoving pastel bricks down girls’ throats?    

Gender and play

Play is an important part of cognitive development.  When children engage in play, they learn through discovery, become familiar with their own limitations, gain a better understanding of spatial relationships, become introduced to cause and effect, and, most relevant to this discussion, play exposes children to societal and cultural norms, as well as family values.  Placing limits on play can affect how a child sees him or herself in the world, which can impact both career and lifestyle choices.   

Research (and experience) has shown that the toys kids choose are shaped by societal expectations; however, these expectations are often dictated by marketing teams and their assumptions of what they think their customers want to see, perpetuating a toy culture that has changed little since the 1950s.  Furthermore, parents may impose toys that are gender “appropriate,” or even punish play that does not align with traditional gender expectations.  But what toys do kids actually want to play with?

In 2003, researchers at the University of Nebraska conducted a study to, in part, identify the impact that stereotyped toys have on play in young children.  There were 30 children who participated in this study, ranging in age from 18-47 months.  They were observed for 30 minutes in a room full of toys, with each toy defined as being traditionally masculine, feminine, or gender neutral.  Interestingly, when assessing the toy preferences of the children, boys tended to play with toys that were either masculine or gender neutral, whereas girls played with toys that were largely gender neutral.  These findings were consistent with previous studies showing that girls tend to play with toys that are not traditionally gendered (i.e. blocks, crayons, puzzles, bears, etc).  
Cherney, et al, 2003
Why is there a disconnect between the natural tendencies of toy choice among female children and what marketing executives deem as appropriate toys for girls?  While fantasy play based on domestic scenarios does have its place during normal development, restricting children to certain types of gendered toys can promote a stereotypical mindset that extends into adulthood, possibly adding to the gender inequity seen in the workplace.  Furthermore, assigning and marketing toys to a specific gender may also contribute to the gendering of household duties and/or recreational activities (i.e. only boys can play hockey or only girls do laundry).

This is obviously problematic for females, especially given the disproportionately low number of women executives and STEM professionals (just to name a few).  However, a conclusion from this study that I hadn’t even considered is the idea that overly feminized toys are not good for boys. 

How “girls only” is disadvantageous to boys

When looking at “masculine” versus “feminine” play, one would see that there is some non-overlap when it comes to learned skills.  For instance, “masculine” play often translates into being able to build something imaginative (like a spaceship or other cool technology) whereas “feminine” toys tend to encourage fantasy play surrounding taking care of the home (like putting the baby to sleep or ironing clothes). 

Both types of learning experiences are useful in today’s world, especially given that more women enter the work force and there is growing trend to more or less split household duties.  So when a kid is being offered toys that encourage play that has both masculine and feminine qualities, there is enhanced development of a variety of skills that ultimately translate into real, modern world scenarios.

However, the issue lies in the willingness to provide and play with strongly cross-gender-stereotyped toys.  Because of the number of toys having this quality, there is a huge gender divide when it comes to play, and boys are much less likely to cross gender lines, especially when toys are overtly “girly” (see figure above).  This is most often because of parents and caregivers who discourage play with “girl” toys, usually citing things like “they will make fun of you.”  Toys heavily marketed to match the stereotypical likes of girls, such as the Friends LEGO kit, clearly excludes boys from engaging in play that develops domestic skills (in addition to pigeonholing girls into thinking that girls can only do domestic things).   

Just yesterday, I came across an article on CNN discussing this issue, and it contained anecdotes similar to the one I described above.  The author described how a little girl was scoffed for having a Star-Wars thermos as well as how a little boy was told (by another little girl) that he could not have the mermaid doll he wanted.  My arguments thus far have been centered on developing a variety of skills through play, but I’d also like to add that limiting self-expression could be disastrous for the future wellbeing of an individual. 

There is some progress being made with regard to how toys are being presented in stores.  For instance, the same article described the new Toy Kingdom at Harrod’s, which does not conform to the traditionally separated “boy” and “girl” sections.  Instead, it has “worlds,” such as The Big Top(with circus acts and fairies) or Odyssey(with space crafts and gadgets).  This type of organization allows any child, regardless of gender, to engage in play that facilitates imagination and cognition.

Hey Toys’R Us, are you listening?                

 Final thoughts

Please don’t misinterpret this as being anti-pink, anti-princess, or anti-feminine.  I embrace my own femininity with vigor and pride.  I like to wear dresses and makeup and get my hair did.  Give me a pair of Manolo Blahniks and I will wear the shit out of them.  But I will do so while elbow deep in a biochemical analysis of intracellular cholesterol transport.    

My point is that if you are going to make a toy more appealing to girls by painting it pink, don’t forget to include facets that allow girls to be comfortable with their femininity while providing an experience that promotes empowerment and an unlimited imagination.  Furthermore, don’t exclude boys from getting an experience that helps them acquire skills that are applicable (and desirable) in the modern world.  As it stands right now, toys like the Friends LEGO kit does neither of these and I believe that they major fails, both of the Double X and the XY variety.    

For more, check out Feminist Frequency’s takedown of LEGO:



References:
Judith E. Owen Blakemore and Renee E. Centers, Characteristics of Boys’ and Girls’ Toys, Sex Roles, Vol. 53, Nos. 9/10, November 2005 [PDF, paywall]

Gerianne M. Alexander, Ph.D., An Evolutionary Perspective of Sex-Typed Toy Preferences: Pink, Blue, and the Brain, Archives of Sexual Behavior, Vol. 32, No. 1, , pp. 7–14, February 2003 [PDF, paywall]

Isabelle D. Cherney, Lisa Kelly-Vance, Katrina Gill Glover, Amy Ruane, and Brigette Oliver Ryalls, The Effects of Stereotyped Toys and Gender on Play Assessment in Children Aged 18-47 Months, Educational Psychology: An International Journal of Experimental Educational Psychology, 23:1, 95-106, 2003

Carol J. Auster and Claire S. Mansbach, The Gender Marketing of Toys: An Analysis of Color and Type of Toy on the Disney Store Website, Sex Roles, 2012 [abstract link]

Isabelle D. Cherney and  Kamala London, Gender-linked Differences in the Toys, Television Shows, Computer Games, and Outdoor Activities of 5- to 13-year-old Children, Sex Roles, 2006 [PDF]

Isabelle D. Cherney and Bridget Oliver Ryalls, Gender-linked differences in the incidental memory of children and adults, J Exp Child Psychol, 1999 Apr;72(4):305-28 [abstract link]

Don’t worry so much about being the right type of science role model

Role models: How do they look? (Source)
[Today we have a wonderful guest post from Marie-Claire Shanahan, continuing the conversation about what makes someone a good role model in science. This post first appeared at Shanahan's science education blog, Boundary Vision, and she has graciously agreed to let us share it here, too. Shanahan is an Associate Professor of Science Education and Science Communication at the University of Alberta where she researches social aspects of science such as how and why students decide to pursue science degrees. She teaches courses in science teaching methods, scientific language and sociology of science. Marie-Claire is also a former middle and high school science and math teacher and was thrilled last week when one of her past sixth grade students emailed to ask for advice on becoming a science teacher. She blogs regularly about science education at Boundary Vision and about her love of science and music at The Finch & Pea.]

What does it mean to be a good role model? Am I a good role model? Playing around with kids at home or in the middle of a science classroom, adults often ask themselves these questions, especially when it come to girls and science. But despite having asked them many times myself, I don’t think they’re the right questions.


Studying how role models influence students shows a process that is much more complicated than it first seems. In some studies, when female students interact with more female professors and peers in science, their own self-concepts in science can be improved [1]. Others studies show that the number of female science teachers  at their school seems to have no effect [2].


Finding just the right type of role model is even more challenging. Do role models have to be female? Do they have to be of the same race as the students? There is often an assumption that even images and stories can change students’ minds about who can do science. If so, does it help to show very feminine women with interests in science like the science cheerleaders? The answer in most of these studies is, almost predictably, yes and no.


Diana Betz and Denise Sekaquaptewa’s recent study “My Fair Physicist: Feminine Math and Science role models demotivate young girls” seems to muddy the waters even further, suggesting that overly feminine role models might actually have a negative effect on students. [3] The study caught my eye when PhD student Sara Callori wrote about it and shared that it made her worry about her own efforts to be a good role model.


Betz and Sekaquaptewa worked with two groups of middle school girls. With the first group (144 girls, mostly 11 and 12 years old) they first asked the girls for their three favourite school subjects and categorized any who said science or math as STEM-identified (STEM: Science, Technology, Engineering and Math). All of the girls then read articles about three role models. Some were science/math role models and some were general role models (i.e., described as generally successful students). 


The researchers mixed things even further so that some of the role models were purposefully feminine (e.g., shown wearing pink and saying they were interested in fashion magazines) and others were supposedly neutral (e.g., shown wearing dark colours and glasses and enjoying reading).* There were feminine and neutral examples for both STEM and non-STEM role models. After the girls read the three articles, the researchers asked them about their future plans to study math and their current perceptions of their abilities and interest in math.**


For the  most part, the results were as expected. The STEM-identified girls showed more interest in studying math in the future (not really a surprise since they’d already said math and science were their favourite subjects) and the role models didn’t seem to have any effect. Their minds were, for the most part, already made up.


What about the non-STEM identified girls, did the role models help them? It’s hard to tell exactly because the researchers didn’t measure the girls’ desire to study math before reading about the role models.  It seems though that reading about feminine science role models took away from their desire to study math both in the present and the future. Those who were non-STEM identified and read about feminine STEM role models rated their interest significantly lower than other non-STEM identified girls who read about neutral STEM role models and about non-STEM role models. A little bit surprising was the additional finding that the feminine role models also seemed to lower STEM-identified girls current interest in math (though not their future interest).


The authors argue that the issue is unattainability. Other studies have shown that role models can sometimes be intimidating. They can actually turn students off if they seem too successful, such that their career or life paths seem out of reach, or if students can write them off as being much more talented or lucky than themselves. Betz and Sekaquaptewa suggest that the femininity of the role models made them seem doubly successful and therefore even more out of the students’ reach.

The second part of the study was designed to answer this question but is much weaker in design so it’s difficult to say what it adds to the discussion. They used a similar design but with only the STEM role models, feminine and non-feminine (and only 42 students, 20% of whom didn’t receive part of the questionnaire due to an error). The only difference was instead of asking about students interest in studying math they tried to look at the combination of femininity and math success by asking two questions:

  1. “How likely do you think it is that you could be both as successful in math/science AND as feminine or girly as these students by the end of high school?” (p. 5)
  2. “Do being good at math and being girly go together?” (p. 5)

Honestly, it’s at this point that the study loses me. The first question has serious validity issues (and nowhere in the study is the validity of the outcome measures established). First, there are different ways to interpret the question and for students to decide on a rating. A low rating could mean a student doesn’t think they’ll succeed in science even if they really want to. A low rating could also mean that a student has no interest in femininity and rejects the very idea of being successful at both. These are very different things and make the results almost impossible to interpret. 

Second these “successes” are likely different in kind. Succeeding in academics is time dependent and it makes sense to ask young students if they aspire to be successful in science. Feminine identity is less future oriented and more likely to be seen as a trait rather a skill that is developed. It probably doesn’t make sense to ask students if they aspire to be more feminine, especially when femininity has been defined as liking fashion magazines and wearing pink.

Question: Dear student, do you aspire to grow up to wear more pink? 

Answer (regardless of femininity): Um, that’s a weird question.

With these questions, they found that non-STEM identified girls rated themselves as unlikely to match the dual success of the feminine STEM role models. Because of the problems with the items though, it’s difficult to say what that means. The authors do raise an interesting question about unattainability, though, and I hope they’ll continue to look for ways to explore it further.

So, should graduate students like Sara Callori be worried? Like lots of researchers who care deeply about science, Sara expressed a commendable and strong desire to make a contribution to inspiring young women in physics (a field that continues to have a serious gender imbalance). She writes about her desire to encourage young students and be a good role model:

When I made the decision to go into graduate school for physics, however, my outlook changed. I wanted to be someone who bucked the stereotype: a fashionable, fun, young woman who also is a successful physicist. I thought that if I didn’t look like the stereotypical physicist, I could be someone that was a role model to younger students by demonstrating an alternative to the stereotype of who can be a scientist. …This study also unsettled me on a personal level. I’ve long desired to be a role model to younger students. I enjoy sharing the excitement of physics, especially with those who might be turned away from the subject because of stereotypes or negative perceptions. I always thought that by being outgoing, fun, and yes, feminine would enable me to reach students who see physics as the domain of old white men. These results have me questioning myself, which can only hurt my outreach efforts by making me more self conscious about them. They make me wonder if I have to be disingenuous about who I am in order to avoid being seen as “too feminine” for physics.

To everyone who has felt this way, my strong answer is: NO, please don’t let this dissuade you from outreach efforts. Despite results like this, when studies look at the impact of role models in comparison to other influences, relationships always win over symbols. The role models that make a difference are not the people that kids read about in magazines or that visit their classes for a short period of time. The role models, really mentors, that matter are people in students’ lives: teachers, parents, peers, neighbours, camp leaders, and class volunteers. And for the most part it doesn’t depend on their gender or even their educational success. What matters is how they interact with and support the students. 
Good role models are there for students, they believe in their abilities and help them explore their own interests.

My advice? Don’t worry about how feminine or masculine you are or if you have the right characteristics to be a role model, just get out there and get to know the kids you want to encourage. Think about what you can do to build their self-confidence in science or to help them find a topic they are passionate about. When it comes to making the most of the interactions you have with science students, there are a few tips for success (and none of them hinge on wearing or not wearing pink):

§   Be supportive and encouraging of students’ interest in science. Take their ideas and aspirations seriously and let them know that you believe in them. This turns out to be by far one of the most powerful influences in people pursuing science. If you do one thing in your interactions with students, make it this.

§  Share with students why you love doing science. What are the benefits of being a scientist such as contributing to improving people’s lives or in solving difficult problems? Students often desire careers that meet these characteristics of personal satisfaction but don’t always realize that being a scientist can be like that.

§  Don’t hide the fact that there are gender differences in participation in some areas of science (especially physics and engineering). Talk honestly with students about it, being sure to emphasize that differences in ability are NOT the reason for the discrepancies. Talk, for example, about evidence that girls are not given as many opportunities to explore and play with mechanical objects and ask them for their ideas about why some people choose these sciences and others don’t.
There are so many ways to encourage and support students in science, don’t waste time worrying about being the perfect role model. If you’re genuinely interested in taking time to connect with students, you are already the right type.
__________________________________________________________

* There are of course immediate questions about how well supported these are as feminine characteristics but I’m willing to allow the researchers that they could probably only choose a few characteristics and had to try to find things that would seem immediately feminine to 11-12 year olds. I still think it’s a shallow treatment of femininity, one that disregards differences in cultural and class definitions of femininity. (And I may or may not still be trying to sort out my feelings about being their gender neutral stereotype, says she wearing grey with large frame glasses and a stack of books beside her).

**The researchers unfortunately did not distinguish between science and math, using them interchangeably despite large differences in gender representation and connections to femininity between biological sciences, physical sciences, math and various branches of engineering.

[1] Stout, J. G., Dasgupta, N., Hunsinger, M., & McManus, M. A. (2011). STEMing the tide: Using ingroup experts to inoculate women’s self-concept in science, technology, engineering, and mathematics (STEM).Journal of Personality and Social Psychology, 100, 255-270.

[2] Gilmartin, S., Denson, N., Li, E., Bryant, A., & Aschbacher, P. (2007). Gender ratios in high school science departments: The effect of percent female faculty on multiple dimensions of students’ science identities.Journal of Research in Science Teaching, 44, 980–1009.

[3] Betz, D., & Sekaquaptewa, D. (2012). My Fair Physicist? Feminine Math and Science Role Models Demotivate Young Girls Social Psychological and Personality Science DOI: 10.1177/1948550612440735


Further Reading

Buck, G. A., Leslie-Pelecky, D., & Kirby, S. K. (2002). Bringing female scientists into the elementary classroom: Confronting the strength of elementary students’ stereotypical images of scientists. Journal of Elementary Science Education, 14(2), 1-9.

Buck, G. A., Plano Clark, V. L., Leslie-Pelecky, D., Lu, Y., & Cerda-Lizarraga, P. (2008). Examining the cognitive processes used by adolescent girls and women scientists in identifying science role models: A feminist approach. Science Education, 92, 2–20.

Cleaves, A. (2005). The formation of science choices in secondary school.International Journal of Science Education, 27, 471–486.

Ratelle, C.F., Larose, S., Guay, F., & Senecal, C. (2005). Perceptions of parental involvement and support as predictors of college students’ persistence in a science curriculum. Journal of Family Psychology, 19, 286–293.

Simpkins, S. D., Davis-Kean, P. E., & Eccles, J. S. (2006). Math and science motivation: A longitudinal examination of the links between choices and beliefs. Developmental Psychology, 42, 70–83.

Stout, J. G., Dasgupta, N., Hunsinger, M., & McManus, M. (2011). STEMing the tide: Using ingroup experts to inoculate women’s self-concept and professional goals in science, technology, engineering, and mathematics (STEM). Journal of Personality and Social Psychology, 100,255–270.


Double Xplainer: Once in a Blue Moon

Full Moon, from Flickr user Proggie under
Creative Commons license.
Tonight—August 31, 2012— is the second full Moon of August. The last time two full Moons occurred in the same month was in 2010, and the next will be in 2015, so while the events are rare, they aren’t terribly uncommon either. In fact, you’ve probably heard the second full Moon given a name: “blue moon”. (The Moon will not appear to be a blue color, though, cool as that would be. More on that in a bit.) What you may not know is that this term dates back only to 1946, and is actually a mistake.

According to Sky and Telescope, a premiere astronomy magazine (check your local library!), the writer James Hugh Pruett made an incorrect assumption about the use of the term “blue moon” in his March 1946 article. His source was the Maine Farmers’ Almanac, but he misinterpreted it. The almanac used “blue moon” to refer to the rare occasion when four full Moons happen in one season, when there are usually only three. By the almanac’s standards, tonight’s full moon is not a blue moon (though there will be one on August 21, 2013).

However, even that definition of “blue moon” apparently only dates to the early 19th century. In its colloquial, non-astronomical sense, a “blue moon” is something that rarely or never happens: like the Moon appearing blue. The Moon is white and gray when it’s high in the sky, and can appear very red, orange, or yellow near the horizon for the same reason the Sun does. As far as I can tell, the only time the Moon appears blue is when there’s a lot of volcanic ash in the air, also a rare event (thankfully) for most of the world. The popular song “Blue Moon” (written by everyone’s favorite gay misanthrope, Lorenz Hart) uses “blue” to mean sad, rather than rare.

I’m perfectly happy to keep the common mistaken usage of “blue moon” around, though, since it’s not really a big deal to me. Call tonight’s full Moon a blue moon, and I’ll back you up. However, because it’s me, let’s talk about the Moon and the Sun and why this stuff is kind of arbitrary.

The Moon and the Sun Don’t Get Along

The calendar used in much of the world is the Gregorian calendar, named for Pope Gregory XIII, who instituted it in 1582. The Gregorian calendar, in turn, was based on the older Roman calendar (known as the Julian calendar, for famous pinup girl Julie Callender Julius Caesar). The Romans’ calendar was based on the Sun: a year is the length of time for the Sun to return to the same spot in the sky. This length of time is approximate 365.25 days, which is why there’s a leap year every four years. (Experts know I’m simplifying; if you want more information, see this post at Galileo’s Pendulum.)

A problem arises when you try to break the year into smaller pieces. Traditionally, this has been done through reference to the Moon’s phases. The time to cycle through all the phases of the Moon is called a lunation, which is about 29 days, 12 hours, 44 minutes, and 3 seconds long. You don’t need to pull out a calculator to realize that a lunation doesn’t divide into a year evenly, but it’s still a reasonable way to mark the passage of time within a year, so it’s the foundation of the month (or moonth).

Many calendars—the traditional Chinese calendar, the Jewish calendar, and others—define the month based on a lunation, but don’t fix the number of months in a year. That means some years have 12 months, and others have 13: a leap month. It also means that holidays in these calendars move relative to the Gregorian calendar, such that Yom Kippur or the Chinese New Year don’t fall on the same date in 2012 that they did in 2011. (The Christian religious calendar combines aspects of the Jewish and the Gregorian calendars: Christmas is always December 25, but Easter and associated holidays are tied to Passover—which is coupled to the first full Moon after the spring equinox, and so can occur in a variety of dates in March and April.)

Another resolution to the problem of lunations vs. Sun is to ignore the Sun; this is what the Islamic calendar does. Months are defined by lunations, and the year is precisely 12 months, meaning the year in this calendar is 354 or 355 days long. This is why the holy month of Ramadan moves throughout the Gregorian year, happening sometimes in summer, and sometimes in winter.

The Gregorian calendar does things oppositely to the Islamic calendar: while months are defined, they are not based on a lunation at all. Months may be 30 days long (roughly one lunation), 31 days, or 28 days; the latter two options make no astronomical sense at all. Solar-only calendars have some advantages: since seasons are defined relative to the Sun, the equinoxes and solstices happen roughly on the same date every year, which doesn’t happen in lunation-based calendars. It’s all a matter of taste, culture, and convenience, however, since the cycles of Sun and the Moon don’t cooperate with the length of the day on Earth, or with each other.

Blue moons in the common post-1946 usage never happen in lunation-based calendar systems because by definition each phase of the Moon only occurs once in a month. On the other hand, the version from the Maine Farmers’ Almanac is relevant to any calendar system, because it’s defined by the seasons. As I wrote in my earlier DXS post, seasons are defined by the orbit of Earth around the Sun, and the relative orientation of Earth’s axis. Thus, summer is the same number of days whatever calendar system you use, even though it may not always be the same number of months. In a typical season, there will be three full Moons, but because of the mismatch between lunations and the time between equinoxes and solstices, some rare seasons may have four full Moons.

The Moon and Sun have provided patterns for human life and culture, metaphors for poetry and drama, and of course lots of superstition and pseudoscience. However, one thing most people can agree upon: the full Moon, blue or not, is a thing of beauty. If you can, go out tonight and have a look at it—and give it a wink in honor of the first human to set foot on it, Neil Armstrong.

The real scandal: science denialism at Susan G. Komen for the Cure®

Double X Science is pleased to be able to repost, with permission, this important piece courtesy of author Christie Aschwanden and the Last Word on Nothing website, focused on the things that science teaches us we still don’t know…but want to find out. 
You’ll notice that the focus of this article is the way that the Komen foundation blames the individual with the disease for having it, relying on what Aschwanden aptly calls “breast cancer’s false narrative.” This “blame the person” tactic seems to be especially common in women’s health, with an emphasis on the way a woman allegedly does the wrong thing or thinks the wrong thoughts or doesn’t work hard enough willing herself well, making her disease her fault, instead of the fault of nature, mutations, cell division gone astray, and the countless other molecular factors that accumulate into what we call “disease.” In the case of breast cancer, it’s not one monolith of disease that the decision to screen will magically stop.
Many thanks to Christie Aschwanden and the Last Word on Nothing for graciously agreeing to this important repost. –The DXS Editors ——————————————–
Is breast cancer threatening your life? This Susan G. Komen for the Cure® ad leaves no doubt about who’s to blame —you are.
Over the last week or so, critics have found many reasons to fault Susan G. Komen for the Cure®. The scrutiny began with the revelation that the group was halting its grants to Planned Parenthood.  The decision seemed like a punitive act that would harm low-income women (the money had funded health services like clinical breast exams), and Komen’s public entry into the culture wars came as a shock to supporters who’d viewed the group as nonpartisan.* Chatter on the intertubes quickly blamed the move on Komen’s new Vice-President of Public Policy, Karen Handel, a failed GOP candidate who ran for governor in Georgia on a platform that called for defunding Planned Parenthood.** Komen’s founder, Ambassador Nancy Brinker, awkwardly attempted to explain the decision, and yesterday, Handel resigned her position. (Whether she’ll receive a golden parachute remains unclear, but former CEO Hala Moddelmog received $277,864 in 2010, despite her resignation at the end of 2009.)
The Planned Parenthood debacle brought renewed attention to other controversies that have hounded Komen in recent years—like its “lawsuits for the cure” program that spent nearly $1 million suing groups like “cupcakes for the cure” and “kites for the cure” over their daring attempts to use the now-trademarked phrase “for the cure.” Critics also pointed to Komen’s relentless marketing of pink ribbon-themed products, including a Komen-branded perfume alleged to contain carcinogens, and pink buckets of fried chicken, a campaign that led one rival breast cancer advocacy group to ask, “what the cluck?”
But these problems are minuscule compared to Komen’s biggest failing—its near outright denial of tumor biology. The pink arrow ads they ran in magazines a few months back provide a prime example. “What’s key to surviving breast cancer? YOU. Get screened now,” the ad says. The unmistakeable takeaway? It’s your fault if you die of cancer. The blurb below the big arrow explains why. “Early detection saves lives. The 5-year survival rate for breast cancer when caught early is 98%. When it’s not? 23%.”
If only it were that simple. As I’ve written previously here, the notion that breast cancer is a uniformly progressive disease that starts small and only grows and spreads if you don’t stop it in time is flat out wrong. I call it breast cancer’s false narrative, and it’s a fairy tale that Komen has relentlessly perpetuated.
It was a mistake that most everyone made in the early days. When mammography was new and breast cancer had not yet become a discussion for the dinner table, it really did seem like all it would take to stop breast cancer was awareness and vigilant screening. The thing about the false narrative is that it makes intuitive sense–a tumor starts as one rogue cell that grows out of control, eventually becoming a palpable tumor that gets bigger and bigger until it escapes its local environment and becomes metastatic, the deadly trait that’s necessary to kill you. And this story has a grain of truth to it—it’s just that it’s far more complicated than that.
Years of research have led scientists to discover that breast tumors are not all alike. Some are fast moving and aggressive, others are never fated to metastasize. The problem is that right now we don’t have a surefire way to predict in advance whether a cancer will spread or how aggressive it might become. (Scientists are working on the problem though.)
Some breast cancers will never become invasive and don’t need treatment. These are the ones most apt to be found on a screening mammogram, and they’re the ones that make people such devoted advocates of mammography.H. Gilbert Welch of the Dartmouth Institute for Health Policy and Clinical Practice, calls this the overdiagnosis paradox. Overdiagnosis is what happens when a mammogram finds an indolent cancer. A healthy person whose life was never threatened by breast cancer is suddenly turned into a cancer survivor. She thinks the mammogram saved her life, and so she becomes an advocate of the test.
Some cancers behave just the opposite of these slow-growing, indolent ones. Researchers now know that some cancers are extremely aggressive from the start. There’s simply no such thing as “early” detection for these cancers. By the time they’re detectable by any of our existing methods, they’ve already metastasized. These are the really awful, most deadly cancers, and screening mammograms*** will not stop them.
Then there are cancers that fall somewhere in between the two extremes. These are the ones most likely to be helped by screening mammography, and they’re the lives that mammography saves. How many? For women age 50 to 70, routine screening mammography decreases mortality by 15 to 20% (numbers are lower for younger women). One thousand women in their 50′s have to be screened for 10 years for a single life to be saved.
So let’s recap. Getting “screened now,” as the Komen ad instructs can lead to three possible outcomes. One, it finds a cancer than never needed finding. You go from being a healthy person to a cancer survivor, and if you got the mammogram because of Komen’s prodding, you probably become a Komen supporter. Perhaps a staunch one, because hey—they saved your life and now you have a happy story to share with other supporters. Another possibility is that the mammogram finds a cancer that’s the really bad kind, but you die anyway. You probably don’t die later than you would have without the mammogram, but it might look that way because of a problem called “lead time bias.” The third possibility is that you find a cancer that’s amenable to treatment and instead of dying like you would without treatment, your life is saved. Here again, you’re grateful to Komen, and in this case, your life truly was saved.
Right now, breast cancer screening sucks. It’s not very effective, and if you measure it solely based on the number of lives saved versus healthy people unnecessarily subjected to cancer treatments, it seems to cause more harm than good. For every life saved, about 10 more lives are unnecessarily turned upside down by a cancer diagnosis that will only harm them. In a study published online in November, Danish researchers concluded that, “Avoiding getting screening mammograms reduces the risk of becoming a breast cancer patient by one-third.”
But it’s not quite that simple. Some people really are helped by mammography screening, and if you’re the one helped, it’s hard to discount that one life. Right now mammography is the best tool we have. Welch, who has spent more time than probably anyone else in America studying this issue, has deemed the decision about whether or not to get breast cancer screening a “close call.”
Reasonable women can decide that for them, the potential benefits outweigh the risks. Other reasonable women will decide that for them, the risks outweigh the potential benefits.
Komen isn’t wrong to encourage women to consider mammography. But they’re dead wrong to imply that “the key to surviving breast cancer” is “you” and the difference between a 98% survival rate and a 23% one is vigilance on the part of the victim. This message flies in the face of basic cancer biology.
Between 2004 to 2009, Komen allocated 47% of it $1.54 billion toward education and screening.  Much of its education messaging promotes the same false narrative as its ads, which means they are not only not furthering the search for a cure, they are harming the cause. By implying that the solution to breast cancer is screening, Komen distracts attention from the real problem, which is that way too many women (and men) are still dying of breast cancer, and screening is not saving them. We still can’t prevent breast cancer, because we don’t know what causes it.
To explain why Komen’s fixation on an unscientific story matters, I want to introduce you to Rachel Cheetham Moro. Moro was a cancer blogger, but she won’t be weighing in on this latest Komen controversy, because she died Monday of metastatic breast cancer. Before she left us, she had plenty to say about the false narrative Komen was peddling. Last October she wrote,
How dare Komen so FALSELY suggest that a screening mammogram is all it takes to avoid metastatic breast cancer? How dare Komen so CRUELLY suggest that “not getting screened for breast cancer in time” would be THE reason and the FAULT of the person with metastatic disease who misses out on all the experiences and joyous events of a long and healthy life that so many others take for granted? How dare you, Komen? How dare you? Continue reading