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

Wordy Wednesday: ‘Tis the season to give the gift of health and life

As we here at Double X Science roll toward the holidays, we’re focusing on a holiday gift-giving theme. This week, we brought you our list of Geektastic Gifts for the geek(s) in your life. 

As we all know, though, this season isn’t only about receiving gifts. It’s also about giving them. During these weeks of the holiday season, we will be highlighting worthy, science- and health-related causes that you can support with the gift-giver in you. 

Today, it’s giving the gift of health and life. For many people around the world, this season and all seasons bring something besides gifts. For many people worldwide, especially children, any season can bring diseases that vaccines can prevent and take lives that vaccines could have saved. ‘Tis this season, though, that can inspire you to help them.

Still looking for a Christmas, Hanukkah, Festivus, holiday-yet-to-be-invented gift for a loved (or tolerated) one? Skip the tsotchkes. Go with measles vaccines. Yes, measles vaccines. According to the Red Cross, measles kills an estimated 450 people each day worldwide and most of those are children.


 


What will it cost?

  • vaccinations for 25 childern: $25
  • vaccinations for 50 childern: $50
  • vaccinations for 100 childern: $100
  • vaccinations for a village: $500

Forget getting your best friend Call of Duty Modern Warfare 3! Get 50 vaccinations instead. In that holiday card to your boss, let them know they’ve vaccinated 25 kids. Splurge on that flat-screen TV with your tax return next year. For now, vaccinate a village–A WHOLE VILLAGE! How do you do it? The Red Cross has made it ridiculously easy! A pull-down menu let’s you select 25, 500, 100, or whole village vaccinations and a few clicks later, you’re buying vaccines online from the Red Cross.

_ ________________________
 
Thanks to DXS contributor @DrRubidium
JAYFK Editor-in-Commandant

   

Geektastic gift-giving ideas from Double X Science!



Shirt available via Zazzle


With the holidays fast approaching, the Double X Science team has come up with a great list of science-themed gifts to help you in your quest for the perfect present.  Not only are these gifts thoughtful, they are full of thought.  So go forth and spread some nerd love this year!

Apparel

Art

Books


DVDs and Music

Games

  • Hometown Puzzle, National Geographic, $39.95 Forget those generic puzzles found on the shelves of cookie-cutter toy stores, this highly personalized jigsaw will tickle the fancy of puzzle-lovers anywhere.  I’m probably going to get this for my mom.  NOTE: You need to order this by 12/13 if you want it by 12/25.
Hands-on

Household

Jewelry

Toys

Other links

We are not the only blog containing geektastic gift suggestions. You can find some other great geeky gift-giving ideas here:


Compiled by Double X Science Editor and MotherGeek Jeanne Garbarino

The Only Mother’s Day Gift Guide You Will Ever Need

Our mothers were nothing like either of these people. (Source)

(Warning: We are having some fun, so what you are about to read does not explicitly contain science but does reference soy, onanism, tubed meats, and vacuums. In keeping with the DXS mission, however, we have embedded a little science here and there in the links. )

While the celebration of mothers is not a new concept, the modern version of Mother’s Day is a far cry from the ancient festivals that honored Cybele.  However, in 1907, when Anna Jarvis invented the modern Mother’s Day as a means to pay homage to her own mother, it was not her intention to use moms for profit.

But, alas, by the 1920s, this well-intended national holiday quickly morphed into the cash cow we see today.  Sure, it is nice to receive a gift, but perhaps capitalism has since stripped Mother’s Day of its original meaning, and for the first week or two in May, we are bombarded with advertisements that claim to know what item every mother must have.  


From this, many sites have done us all the great favor of curating these cannot-live-without gifts into a single, easy to navigate list (financial kickbacks notwithstanding), often broken down into natural June Cleaveresque categories like “kitchen” and “for the home” (read: how to cook for everyone and keep shit clean). Besides the fact that these lists can be generalized to every gift-giving holiday for the lovely lady in your life, even Don Draper himself would scoff at many of these suggestions.  

Because we at DXS wish to ensure that your Mother’s Day experience is the best it can possibly be, we present you with a different kind of list – one that provides the most valuable unsolicited advice you will ever receive when it comes to choosing for dear old mom.  Here, you will be schooled on what not to get for the woman that gave you life.   

  1. Flowers. One of the most suggested gifts for Mother’s Day is flowers. What woman doesn’t love flowers? Well, one who does not need one more thing to water, or sees her own mortality in each dried up petal aimlessly floating down onto the floor that had just been cleaned. Oh, and those tears you see building up in our eyes? Not tears of joy. You better back up or you might get caught in a sneezing fit of fury because, frankly, the last thing we want to do on “our” day is pretend that we like feeling like our heads will explode. And let us not forget how those flowers came to be available in your local flower shop or supermarket in the first place… from Colombia?

  1. Soy Candles.  Soy. For the last decade or two, we have seen the magical benefits of this plant product popping up in pseudoscientific “reports” in quality magazines like First for Women. And now, soy-pushers all over the intertubes will willingly exclaim that soy is the superior material for the production of candles, allegedly “soot free” (they aren’t really). Sure, anything soy-based will help the American Soy Farmer keep up with the Joneses, but a candle is a candle and unless you are also giving me a golden ticket to enjoy its inherent ambience whilst I soak in my imaginary claw-footed tub, full of bubbles and rose petals and the sultry sounds of Barry White, save it. Plus, I’d rather not burn my house down (again).

  1. Gift Baskets! What says “I admire you like a work colleague” more than a gift basket?  Sure, smoked cheeses and tubed meats taste fine after a few martinis, but when enjoying such delicacies, I prefer to do it while watching my co-workers photocopy their ass cheeks. Some things just don’t have the same effect in the home.  

  1. Teething Necklace. One website was flashing necklaces all over the place – but these weren’t just any old necklaces – they doubled as teething necklaces for the baby.  Anyone who knows anything about a teething baby knows that, despite the alleged pain babies feel (hey, I don’t remember it, do you??), moms suffer the most. So instead of the necklace, why don’t you go ahead and take the dang baby for a few hours and give me a much deserved break? I’ll even sweeten the deal and throw some Tylenol in the diaper bag. And, in the strange and rare event that I might want rope burn on my neck, I’d rather get it from some fantasy role-playing in the boudoir. Take that as you will.

  1. Vacuum Cleaner. If you really think that I want another reminder of how much I have to pick up after you and all of your friends – who regularly come over and wipe out all of the food I just deposited into my refrigerator – then yes, go ahead and buy me a vacuum. I mean, it is not like I don’t already spend all of my “free” time vacuuming the floors, so why not give me the gift that embodies what you really think of me (your maid)? Plus, Dyson has been showing commercials non-stop for a sale that runs until Mother’s Day, with the clear implication to get your mother (or if you are a mother to get yourself) a vacuum for Mother’s Day. So if you do decide to get a vacuum, make sure you have $500 for it. Remember, though, that a vacuum is really empty space, so you might want to consider getting me something more tangible–and fun.

  1. 50 Shades of Gray. Well, maybe I am not too opposed to this, but let it be known that I will probably need about ten minutes (give or take) of “alone” time after each time I pick up this series. As long as you are OK with this, I am OK with this. By the way, did you know that there are really more than 50 shades of grey?
We hope you will seriously consider this advice. After all, we really don’t need more shit to take care of, water, clean with, or… actually, we can always use some more good reads. Happy Mother’s Day!

Are your children always on your mind? They may be IN your mind

Hmm. Do I have any cells in there?
On Mother’s Day this year, we told you why, if you have biological children, those children are literally a part of you for life thanks to a phenomenon called microchimerism. When a woman is pregnant, some of the fetal cells slip past the barrier between mother and fetus and take up residence in the mother. What researchers hadn’t turned up in humans before now was that some of those cells can end up in the mother’s brain. Once there, according to a study published today in PLoS ONE, they can stick around for decades and, the researchers suggest, might have a link to Alzheimer’s disease. Note that is a big “might.”

The easiest way to tell if a fetal cell’s made it into a maternal tissue is to look for cells carrying a Y chromosome or a Y gene sequence (not all fetuses developing as male carry a Y chromosome, but that’s a post for another time). As you probably know, most women don’t carry a Y chromosome in their own cells (but some do; another post for another time). In this study, researchers examined postmortem brain tissue from 26 women who had no detectable neurological disease and 33 women who’d had Alzheimer’s disease; the women’s ages at death ranged from 32 to 101. They found that almost two thirds (37) of all of the women tested had evidence of the Y chromosome gene in their brains, in several brain regions. The blue spots in the image below highlight cells carrying these “male” genes a woman’s brain tissue.

Photo Credit: Chan WFN, Gurnot C, Montine TJ, Sonnen JA, Guthrie KA, et al. (2012)
Male Microchimerism in the Human Female Brain. 
PLoS ONE 7(9): e45592. doi:10.1371/journal.pone.0045592

The researchers also looked at whether or not these blue spots were more (or less) frequent in the brains of women with Alzheimer’s disease compared to women who’d had no known neurological disease. Although their results hint at a possible association, it wasn’t significant. Because the pregnancy history of the women was largely unknown, there’s no real evidence here that pregnancy can heighten your Alzheimer’s risk or that being pregnant with or bearing a boy can help or hinder. As I discuss below, you can end up with some Y chromosome-bearing cells without ever having been pregnant.

Also, age could be an issue. Based on the reported age ranges of the group, the women without Alzheimer’s were on average younger at death (70 vs 79), with the youngest being only 32 (the youngest in Alzheimer’s group at death was 54). No one knows if the women who died at younger ages might later have developed Alzheimer’s. 

Indeed, most of this group–Alzheimer’s or not–had these Y-chromosome cells present in the brain. The authors say that 18 of the 26 samples from women who’d had no neurologic disease were positive for these “male” cells–that’s 69%–while 19 of the 33 who had Alzheimer’s were. That’s 58%. In other words, a greater percentage of women who’d not had Alzheimer’s in life were carrying around these male-positive cells compared to women who had developed Alzheimer’s. The age difference might also matter here, though, if these microchimeric cells tend to fade with age, although the researchers did get a positive result in the brain of a woman who was 94 when she died.

Thus, the simple fact of having male-positive cells (ETA: or not enough of them) in the brain doesn’t mean You Will Develop Alzheimer’s, which is itself a complex disease with many contributing factors. The researchers looked at this potential link because some studies have found a higher rate of Alzheimer’s among women who’ve been pregnant compared to women who have not and an earlier onset among women with a history of pregnancy. The possible reasons for this association range from false correlation to any number of effects of pregnancy, childbearing, or parenting.

Nothing about this study means that migration of fetal cells to the brain is limited to cells carrying Y chromosomes. It’s just that in someone who is XX, it’s pretty straightforward to find a Y chromosome gene. Finding a “foreign” X-linked gene in an XX person would be much more difficult. Also, a woman doesn’t have to have borne a pregnancy to term to have acquired these fetal cells. As the authors observe, even women without sons can have these Y-associated cells from pregnancies that were aborted or ended prematurely or from a “vanished” male twin in a pregnancy that did go to term. 

In fact, a woman doesn’t even have to have ever been pregnant at all to be carrying some cells with Y chromosomes. Another way you can end up with Y chromosome cells in an XX chromosome body is–get this–from having an older male sibling who, presumably, left a few cellular gifts behind in the womb where you later developed. As the oldest sibling, I can only assume I could have done the same for the siblings who followed me. So, if you’ve got an older sibling and have been pregnant before–could you be a double microchimera? 

But wait. You could even be a triple microchimera! This microchimerism thing can be a two-way street. If you’re a woman with biological children, those children already carry around part of you in the nuclear DNA you contributed and all of the mitochondria (including mitochondrial DNA) in all of their cells. Yes, they get more DNA from you than from the father. But they might also be toting complete versions of your cells, just as you have cells from them, although fetus–>mother transfer is more common than mother–>fetus transfer. The same could have happened between you and your biological mother. If so, a woman could potentially be living with cells from her mother, older sibling, and her children mixed in with her own boring old self cells.

The triple microchimera thing might be a tad dizzying, particularly the idea that you could be walking around with your mother’s and sibling’s cells hanging out in You, a whole new level of family relationships. But if you’re a biological mother, perhaps you might find it comforting to know that a cellular part of you may accompany your child everywhere, even as your child is always on your mind–and possibly in it, too.

Motherhood Defined: It is in the heart of the beholder

“Motherhood”: Sculpture at the Catacumba Park, Rio de Janeiro, Brazil
Motherhood.  It can mean many things, and our own definition of it is largely defined by our individual experiences.  To one person, motherhood might simply mean the act of raising children; to another, motherhood might be what defines them.  

It is not uncommon to generalize the concept of “motherhood” and lump everyone who upholds a single criterion – being a mom – into one group.   But, really, motherhood affects us all in one way or another, and that way is as unique as the pattern of curves and ridges on a fingertip.

Despite the recent outbreak of (heated) discussion surrounding the Time cover story depicting a beautiful and young woman nursing a toddler, and the questioning if following a certain philosophy makes one more or less of a mother, humans, as a whole, are truly bound by a common goal: to raise the next generation to the best of our abilities under the circumstances at hand.   
But, there is no one answer.
Every mom will have her own definition of motherhood.  But, being a mom is by no means a prerequisite for understanding motherhood as it relates to an individual.  For this special Mother’s Day post, we would like to pay homage to motherhood in its many forms.  Here you will not find a singular description of motherhood.  What you will find, however, is what it means on a more personal level, which is to say that the definition can only come from the heart. 

Thank you to all of the wonderful people who participated in this project (and with short notice!) – we have answers in paragraph, tweet, and prose forms.    

Ilina Ewen, Blogger at Dirt and Noise@IlinaP

What does motherhood mean to me?

Motherhood means feeling a kaleidoscope of emotions simultaneously – fear, glee, worry, angst, pride. And it means being an advocate and a revolutionary who empowers her children to engage in society in a meaningful, fun, vibrant way. And lastly, motherhood means always giving up the biggest piece of cake and the last popsicle and being okay with that.

Momma, PhD, Scientist/Wife/Mother

Motherhood means accepting responsibility. If you read the news or listen to the hype, you know what I mean.  Every choice you make, from before a child is conceived, until long after you’re dead, there is someone out there that will tell you how it impacted your kid. As my nana always said, “It’s always the mother’s fault.”  I just hope that as the time passes I get more credit than blame for how my kids turn out.

Motherhood is how you stretch your heart in ways you never thought possible. It’s how you love through the ups & down, the challenges that life brings. And, it lasts a lifetime from that first tiny cry. 

Chris Gunter, Director of Research Affairs, HudsonAlpha Institute for Biotechnology, @Girlscientist

I’m a human geneticist by training, so I’ve been told having a child is the ultimate version of participating in my research. But the science analogy that best summarizes it for me is maternal-fetal microchimerism. Data demonstrating that my son and I each likely have some of each other’s intact cells inside us forever — as I have with my mother, and she with hers, and so on — beautifully represent to me the meaning of motherhood. As the quote from Elizabeth Stone goes, having a child “is to decide forever to have your heart go walking around outside your body.” To me, that includes half my DNA, some of my cells, and so many of my hopes and dreams, all in one sweet, kissable package.

Dr. Cheryl G. Murphy, Optometrist and Science Writer, @MurphyOD

Motherhood: As a mom of triplets, some would say I have triple the work but I like to think of it as triple the hugs, triple the joy, triple the fun! And when people ask me what it’s like to become a mom I tell them “it’s the toughest job you’ll ever love.” Happy Mother’s Day to all of you amazing, do-it-all moms out there! 

Matt Shipman, Science writer, and founder of the First Step Project@Shiplives

I’m a man, so I obviously have no first-hand experience as a mother. That said, I was raised by a (wonderful) single mother, and have had the pleasure of watching my wife be an awesome mom to our three daughters. Those experiences have shaped my impressions of motherhood. To me, motherhood means being kind, but honest. Being gentle, but strong. Being nurturing, but encouraging independence. Motherhood is letting your kids think you are ten feet tall and bulletproof, so they feel you can keep them safe — even though there’s stuff out there that scares the hell out of you. It’s encouraging your kids to learn new things and to work their butts off in school, without making them feel stupid. Motherhood is leading by example when it comes to telling right from wrong, and showing your kids which battles are worth fighting. And, when the time comes, motherhood is letting go of the reins to see where the kids go on their own. Motherhood is not for wimps.

Julie Marsh, VP of Operations, Cool Mom Picks + Cool Mom Tech@coolmompicks@coolmomtech 

To me, motherhood means leading by example in the most pivotal role I’ve ever accepted.

Emily Willingham, PhD, managing editor, Double X Science, science writer and editor, biologist, autism parent, mother, @ejwillingham

The greatest realization of motherhood for me was that the children we have are people of their own, not “our” children or some kind of nutty, messy, screaming, demanding “other” invading our space, disrupting our lives, and taking our precious time. They are people I love to have around me because they make me laugh, they bring out the teacher in me (not hard to do), they are cool and interesting and imaginative and fun, and each of them (I have three) is a complete individual with a unique personality, outlook, potential, talent, and beautiful, beautiful face that I love to see every day. Just as I choose to spend time with others whom I love, respect, admire, and laugh with, I choose to do the same with my children. That said, I also still have what I had before my children arrived–a happy, full busy life with a partner to whom I seem to grow closer every day, and work that I love. Thanks to my children, I’ve got something even more–three more wonderful people added to my life whom I am deeply delighted and, frankly, honored to know. As Bill Murray’s character in Lost in Translation observes, “They learn how to walk and they learn how to talk… and you want to be with them. And they turn out to be the most delightful people you will ever meet in your life.”

Alice Callahan, Science of Mom@Scienceofmom

What does motherhood mean to me?

Motherhood is humbling. Of all the endeavors I have tackled in my life, never have I wanted so badly to get everything right and yet known that I would not. Never have I been so emotionally invested in the results, so exhausted by the labor of it, and also, so strangely confident that it will turn out OK. It is the most human thing I have ever done.

David Wescott, It’s not a Lecture@dwescott1

For men whose ideas of fatherhood were shaped in large part by its absence in our own lives, motherhood may mean something a bit different.  I’m by no means a scholar, but I’ve had the opportunity to speak often and at length with women across the globe on this topic, and to curate their thoughts a bit. These women talk about the feeling of connection to their children they know no one else has.  They describe the magic of watching their little ones narrate the moments of discovery in their lives. They talk about how their children “complete the circle” and teach them the other side of unconditional love. They help you understand why people invoke the lioness or the grizzly when describing the protective instinct.  

My perspective of motherhood is a lot like that last sentiment – it’s the unyielding power that rises up in you when you realize a little person depends on you for everything.  I know that many men step up when left in that situation – I’ve seen it first-hand – but I suspect the feeling is different for women because this little person actually came from you, is an extension of you, is connected to you in ways no man will ever fully understand. 

When I think of motherhood, I think of unconditional love. It’s what my mother gave to me, and it’s what I expect I would feel for the children I don’t intend to have. My mother made countless sacrifices for me, but she was independent and did not allow motherhood to define her. She has always encouraged me to be my own person and chase my own dreams. She didn’t want me to feel constrained by gender roles. I feel fortunate to live in a time when motherhood is a choice, not an obligation. I admire my peers who have chosen to have kids, but I’m content to enjoy the rich mother-daughter relationship I have with my mom without feeling obliged to replicate it. 

Editors note: Christie has recently written a wonderful piece on motherhood at Last Word On Nothing.  Go read it!

Carin Bondar, Blogger and Filmmaker for Scientific American, the David Suzuki Foundation and Huffington Post, @drbondar

As a working mother of 4 very young children, I don’t have much time to reflect on much – this stage of my life is pretty much dedicated to surviving.  I do know that once I decided that I really wanted to start having children (when I was almost finished my PhD) – my life seemed oddly empty.  It was as though I realized that something tremendous was missing and I became completely obsessed with wanting them.  Now that I have them (yes all 4 of them!) there are many times when I feel completely overwhelmed and exhausted, but  I will always remember the feelings of desire to have a family.  I know that my life would be empty and incomplete without my lovely babies.

Jeanne Garbarino, Biology Editor at Double X Science and Rockefeller University Postdoc, @JeanneGarb

For five years, I have been a mother.  I have learned – and am still learning – some very difficult lessons on time management and prioritization, on choosing my battles wisely, and on being ok when things aren’t exactly perfect (or even decent).  But, to be honest, these are all lessons I really needed to have in my life.  Though it might seem a bit counterintuitive, the mostly delightful chaos associated with rearing my girls has given me more focus.  For me, motherhood is more of a state of being, and it has helped me learn how to not sweat the small stuff (for the most part), to be more mindful of the present, and to think more about the future.  Oh, and motherhood also gives me that special golden ticket to buy really cool games and toys (because who isn’t interested in seeing what Doggie Doo is all about), as well as provides a dependable companion for roller coaster rides.

Motherhood had made me stand in my living room as my kids run around me and think how odd it is that I protect these three little persons. Motherhood has made me weep at the sight of children hurt or hungry; has made me rageful at a world where monsters are free; has made me face my own capacity for anger; and it has graced me with random gifts like hysterical laughter over blueberry waffles at the breakfast table. 

Rebecca Guenard, PhD, Atomic-o-licious@BGuenard

Motherhood

Listening to stories,

admiring all they know.

Hugging, kissing,

holding Cheeto-covered hands.

Tightening hockey skates,

washing baseball uniforms.

He stands on the mound alone.

From Twitter

@Scientistmother: motherhood means joyous bittersweet scary make a better person love no matter what

@Cbardmayes: mh=if my heart was as the universe, still would not be big enough to hold all the love for my son & his smiles #happymunkimama

@Labroides:motherhood is seeing my wife find reserves of strength patience and love that we didn’t know she had

@Babyattachmode:to me motherhood means realizing that I have this enormous amount of love for such a little person!

@Jtothehizzoe:The “motherhood” is that end of town where all the moms hang out, actin’ all hard, right?

Chemistry sets and the power of hands-on science


Gawker is a site that prides itself on its snark. We here at Double X Science are a sober {snork}, somber {blerp}, sincere {bwahahahahahaaha!} bunch, however. So when we saw, thanks to DXS contributor Dr. Rubidium, that Gawker writer John Cook had cheekily maligned…gasp…chemistry sets for kids in his post, “Horrible Christmas Gifts for the Children of People You Hate,” of course our somber, sincere, sober, snarkless selves had to say something about that.

First, here’s a little of what Gawker said:

“I can’t fathom any parent voluntarily buying one for their child.”
Struggle no more. I am one such parent.

“The ‘sweet spot’…would be about 8 years old.”Magical, isn’t it? 
That’s exactly the age that I got mine! From my parents!

“One of the chemical consequences of heat is your house burning down.”
Actually, heat is one of the consequences of your house burning down, but let’s not quibble.

My personal experience was that a chemistry set flipped the flickering light of my interest in science permanently to “on.” As my author biography attests, it was the preserved frog in the chemistry set that I received at, yes, age 8 that set off a lifetime of scientific pursuit. 

And I’m not alone about that frog.Interested to find out of other science-bent folk had also fallen in love with science over a chemistry set, I sent out a Twitter appeal last night in the role of Double X Science SciMaven: 

If you ever got a chemistry set as a gift…how did you feel abt it? If you have a child…same Q.

Here are some of the responses I received. 

Now the Daddle? We’re on board with the ridiculousness of that.

Emily Willingham, Double X Science Editor

Friday Roundup: Crabs and Lady Gaga, exploring Mars, female orgasm, gift lists, and more!

Find these great women-in-science ornaments here.


Women in science, women and science

Women and men and science
Weird and wonderful science


Yeti crabs, dancing to Lady Gaga. Yep, scientists know how to rock it OUT!




Can’t get enough of dancing crabs? More here

  • Wasps may remember your face, so next time you might get stung, be sure to wear a Nixon mask.
  • Ambien waking the near dead? It’s an unexpected outcome for a sleep drug.
  • Making viruses the natural way. Virus tinkering, Frankviruses, threatened global pandemics…or not?


Science brings the fun…and not just in the form of dancing crabs