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.
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.
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.
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.
Prenatal care and treatment access are big factors.
By Laura Newman
Last week, the media got all excited about the possibility of a cure for HIV perinatal transmission. What was lacking was the recognition that the public remains largely ignorant about HIV in pregnant women. Yet with good wellness care, prevention, HIV testing, and medication,HIV transmission from mother to child can be close to zero. The public needs to know that women who are pregnant and HIV positive can also live good-quality lives, as can their children.
Thanks to Dr. Judy Levison, an obstetrician/gynecologist whose career centers on caring for HIV-pregnant women, I began to learn how scientific advancements in HIV-care make it possible for pregnant women with HIV and HIV-positive men to have children and not transmit the virus to their newborns. In the midst of this learning experience, I found out that a young woman I know, “Angela*,” was HIV positive and wanted to plan a pregnancy. I was shocked; I knew plenty of gay men with HIV, but rarely had I met a woman who had contracted the virus. Planning a pregnancy while being infected with HIV was something that I couldn’t imagine.
“Angela” is married and has lived with HIV for some years, with a low viral load by taking good care of herself and taking recommended antiretroviral therapy, when needed. She sought artificial insemination, one of several options available to HIV-affected couples. It worked. When she was planning her pregnancy, her parents were resistant. They worried that even though she is healthy now, that might change. They couldn’t imagine being saddled with taking care of a young child. Her parents’ resistance reminded me of the old coming-out stories we used to hear and how parents adapted to learning their child is gay. To their credit, both parents soon rose to the occasion. Angela and her spouse have a healthy toddler, and the grandparents love spending time with him.
Angela’s story isn’t everyone’s story. The hubbub at the recent 20th Conference on Retroviruses and Opportunistic Infections was not on the “functional cure” of the baby born to a pregnant woman with HIV, but on why, in this day and age, the mother doesn’t seem to have received the recommended prenatal care and antiretroviral therapy herself. Under what circumstances did she deliver? How did mom and baby get lost in the healthcare system? It’s far too easy to be captivated by a potential breakthrough and forget that plenty of people don’t get access to basic science-backed care that prevents HIV transmission in the first place.
As I describe below and as Angela’s experience illustrates, a lot of evidence shows that it is very safe for women with HIV to get pregnant, have healthy babies, and not transmit HIV to their children. Unfortunately, for many pregnant women with HIV, harsh judgments and inaccurate assumptions often carry the day. Let’s just say that HIV-positive moms and their kids have not earned the acceptance allotted to, say, a Magic Johnson, who has had HIV for decades, and with good HIV and wellness care, lives a good-quality life.
These inroads in science-based HIV prevention and care that have helped Johnson so much lag behind in poor and minority communities in the United States and low-resource countries around the world. HIV disproportionally affects African-Americans in the United States, and access to care, Medicaid cuts, and poverty reduce the chance that many people in need will receive good state-of-the-art prevention (regular testing, practicing safe sex, not sharing drug needles) and wellness care. Perinatal transmission could well rise in these communities.
Facing down ignorance
At first, being pregnant was not easy for Angela — not because her pregnancy was hard (it was not) — but because of the uneasiness some of her coworkers expressed about her becoming pregnant as an HIV-positive woman. Even though Angela worked in healthcare, some of her coworkers thought she had no business being pregnant. When she complained to her supervisor, the manager urged Angela to take it upon herself to educate staff about scientifically proven treatments for pregnant women with HIV that help moms stay well and prevent transmission to the baby. Angela asked instead for an in-service training, which was scheduled. Her colleagues’ attitudes turned around after the in-service.
It meant a lot to her to change the culture.
Angela had a normal term delivery, gave birth to a healthy baby, who is now a toddler, with no sign of HIV infection. Angela’s viral load remains undetectable. They are living healthy, high-quality lives like many other families, moms, and children.
The parents and prenatal planning
The ideal in the setting of HIV infection is that both partners are involved in preconception planning. Prevention of transmission of HIV from an HIV-positive father to an HIV-negative mom and fetus is now possible. The door is now open to HIV-positive men and women who want families but have HIV. Any plans they had to become parents have not simply vanished.
HIV research has advanced to the point that we now know that if HIV-positive individuals work with knowledgeable medical providers and have good access to proven practices, parents and children do quite well. Essential practices include:
Before trying to conceive, people should take antiretroviral drugs and have their infection under control, shown by a low viral load or undetectable levels of the virus (“undetectable” levels vary, depending on the lab) in their blood;
Couples are instructed to have unprotected sex only when the woman is ovulating. Current guidelines recommend using an ovulation prediction kit, which you can purchase at most drugstores.
Artificial insemination is another option that HIV-affected couples are using, as Angela did.
HIV testing is recommended routinely for all pregnant women, as well as for all non-pregnant adults and teens.
If a woman learns during her pregnancy for the first time that she is HIV infected, she can work with her healthcare provider to stay healthy, prevent mother-to-child transmission, and prevent passing HIV to her partner.
In general, people infected with HIV who are not pregnant begin taking anti-HIV medications when their CD4 counts fall below 500 cells/mm3 (HIV targets these immune cells and destroys them, compromising a person’s immunity). The medication regimen during pregnancy depends on whether or not you are taking medication to improve your own health or just your baby’s. In many cases, healthy women delay starting antiretroviral medication until the second trimester, which is when all women should be on HIV medication. However, HIV medication and interactions with other drugs and the fetus are complicated and require consultation with a physician. If women are diagnosed later in a pregnancy, they should start HIV drugs then. You can find detailed recommendations here.
During childbirth, women whose viral loads are still undetectable can have normal vaginal deliveries. However, according to the National Institutes of Health and other authorities, scheduled cesarean delivery at 38 weeks of gestation is recommended to reduce perinatal transmission of HIV for women with HIV-RNA levels >1,000 copies/mL or unknown HIV levels near the time of delivery, regardless of whether they were taking recommended antiretroviral drugs during pregnancy. The guidelines state that when there is a low rate of transmission (viral loads lower than 1000 copies/mL), the benefits of a scheduled c-section are unclear. Dr. Levison, an obstetrician/gynecologist at Baylor College of Medicine, Houston, TX, says that in her practice, women rarely need a cesarean section.
The newborn child
In the United States, breastfeeding is discouraged because HIV can be transmitted in breast milk. According to the Centers for Disease Control and Prevention (CDC), the risk for HIV transmission goes up as much as 45%. However, the topic of breastfeeding remains controversial. In healthy women with no HIV history, the broad consensus is that breastfeeding is best, giving babies excellent nutrition and helping the infant bond with mom. And many parts of the world have problems with sanitation and dirty water, making breastfeeding preferable to mixing formula. Outside of the US, according to Levison, in the UK, breastfeeding guidelines are more liberal. Furthermore, in some cultures, women are afraid not to breastfeed for fear that they will be outed as having an HIV infection, according to Levison, so many treating physicians adapt practice to the culture, preferences of the mom. Internationally, for example, in Africa, women often breastfeed and remain on antiretroviral drugs during that time. Formula is also costly. In the US, poor moms are eligible for formula through the federal Women’s Infants and Children’s nutritional support program.
Besides breastfeeding, HIV-positive moms need to know that pre-chewing of food before feeding baby is a transmission risk.
As soon as a woman goes into labor and during childbirth, the infantmust begin a six-week course of the antiretroviral medication zidovudine (AZT). Current guidelines also state that the baby should be tested for HIV at 14 to 21 days, at 1 to 2 months, and again at 4 to 6 months. If the viral load remains undetectable after two tests, the baby is considered to not have gotten HIV.
Resolving resource disparities
The moms, dads, and kids with HIV have enormous potential to live healthy lives for decades on proven antiretroviral drugs.
In fact, a December 2012 CDC Fact Sheet states that the number of women with HIV giving birth in the United States increased approximately 30% from 6,000 to 7,000 in 2000 to 8700 in 2006. During that same time frame, the estimated number of perinatal infections per year in all 50 states and 5 dependent areas continued to decline.
It’s not all good news, though, because of marked disparities in resource allocation and pre- and perinatal care. According to CDC data, 63% of perinatal infections were in blacks/African-Americans; 22% were in Hispanics/Latinos, and 13% were in whites. That leaves a lot of work to be done in enhancing targeted prevention programs.
Another recent milestone is that the US Preventive Services Task Force is finally about to endorse universal HIV testing, long after the CDC backed such a move in 2006. This milestone is important to because it is also linked to health reform. All public and private health plans are required to provide coverage for U.S. Preventive Services Task Force-recommended preventive services without patient copayments.
With this availability, perhaps women might learn about an HIV infection before they become pregnant, giving them time to have their own treatment in place before it is too late to protect the baby. The case report of the baby cured of HIV gives a lot of hope, but even more preferable would be preventing HIV infection in the first place, through safe sex and not exchanging needles. Once people become infected, for whatever reason, their lives should no longer be viewed as if they are at in a holding pattern until death.
The world needs to know that just like every other mom, dads and pregnant women with HIV can parent children, stay healthy, and not transmit the virus to their babies. Paramount in this is universal HIV testing for adults and teens, prevention programs, and ensuring scientifically proven treatment of the mother before, during, and after her pregnancy.
Over the last few months, the concept of birth control has been under great scrutiny in the American eye. Many politicians have been discussing it’s “moral” implications, and whether institutions or organizations should have the right to deny insurance coverage for hormonal contraception if it does not fall within the confines of their belief systems. And while American women have narrowly escaped legislation that would impede their reproductive health and freedom, politicians, mostly men, feel it necessary to make misinformed or even completely false statements about birth control.
For some strange reason, there is this erroneous idea that birth control is not a matter of health, but rather a means by which a woman can engage in careless and frequent sexual activity, with a man, and without the consequences of pregnancy. It’s clear that the picture these politicians are trying to paint is that of debauchery and immorality, which, of course, is a departure from the puritanical integrity they embody. But, rather than focus on this utter nonsense, I would prefer to highlight the significant impact birth control will have on the future of our civilization and our planet.
The human population has grown steadily since the beginning of our species. However, the rate of growth began to skyrocket after the industrial revolution, and our population has actually doubled over the last 50 years, reaching 7 the billion mark in March of this year. This is an astounding statistic since it took until 1804 – around 50,000 years – to reach our first billion.
World Population: 1800 – 2100 (Wikimedia Commons)
What makes these numbers really scary is the concept of carrying capacity, which is an ecological term used to describe the maximum number of individual members of a species that a certain habitat can support. In this case, the species is human and that certain habitat is planet earth.
Here’s the thing: the availability of our resources will not match the rate of population growth. Given our current technologies, there is only so much food we can grow, only so much water we can drink, only so much space we can inhabit, only so much waste we can safely rid, only so much energy we can harness. There will be a point that the human population will hit its carrying capacity on earth, and when it does, the chances of widespread famine will be great, and the delineation between the developing world and the developed world will be no longer.
Given this very serious issue, Britain’s Royal Society has recently convened to discuss the future of the human population and on April 26th, 2012, and published their findings in the People and the Planet Report [PDF]. For me, key findingnumber three struck a cord:
Reproductive health and voluntary family planning programmes urgently require political leadership and financial commitment, both nationally and internationally. This is needed to continue the downward trajectory of fertility rates, especially in countries where the unmet need for contraception is high. (emphasis theirs)
Political leadership and financial commitment – Did you see that, American politicians?? For those of you who are unnecessarily waging war on women’s reproductive rights, its time to get your giant heads out of your collective asses and realize the implications of legislation that would go against ensuring both the continued success of our species and the health of our planet. It is time to stop spending money on these regressive and oppressive campaigns guised under the false pretense of “religious freedom” and start making a financial commitment to the women (and by association, men) who live in our nation.
To drive this point even further, here is another excerpt from the People and the Planet Report (my favorite bit, found in Box 2.5 on page 33):
Women bear the main physical burden of reproduction: pregnancy, breastfeeding and childcare. They also bear the main responsibility for contraception as most methods are designed for their use. Men, it may be argued, reap the benefits of children without incurring an equal share of the cost. It follows that women may be more favourable to the idea of small families and family planning than their partners but unable to express their inclinations in male-dominated systems. Such views received international endorsement in the Program of Action resulting from the UN conference on population in 1994. Paragraph 4.1 states that “improving the status of women is essential for the long-term success of population programs”.
We currently live in a nation where 99% of women who are of reproductive age have used some form of birth control at least once. And when it comes to hormonal contraception, over 80% of sexually active women aged 15-44 have relied on “the pill” as a means to prevent unwanted pregnancies. This has contributed to an average of two births per American woman, which is considered to be the replacement rate for a population. Compare this number to countries where birth control and reproductive education is scarce – countries like Niger (7.52 births per woman) or Afghanistan (5.64 births per woman) – and one can see the impact of family planning through contraception. Furthermore, it has been well documented that women in developed worlds who are provided with the means to control their fertility are more empowered and their families are healthier.
While our situation in the US is significantly better compared to underdeveloped nations where rape and the cultural devaluing of women is commonplace, we still have a responsibility to uphold – a responsibility that would undoubtedly increase the quality of life for women (and men), as well as contribute to the overall health of the human population. Why would we want to go backwards and remove the ability of a woman to decide when, if ever, she would like to reproduce?
Having access to birth control empowers women and allows them to make greater contributions to society. And because contraception is primarily the responsibility of a woman, our society needs to ensure that birth control, reproductive education, and family planning resources are readily available to EVERYONE.
The United Nations predicts that the ten-billionth person will be born around 2050. Will we continue to fight this ridiculous fight against women’s rights or will we redirect our collective energy to developing technologies that will help our species and planet better cope with the increasing demands associated with a steadily rising population? Let’s stop allowing stupidity to prevail and let’s start doing the right thing: making sure that birth control is readily available to any woman who wishes to use it. Because, now more than ever, it is clear that birth control will save the world.
Note: In my readings for this article, I came across a wonderful resource for anyone interested in learning more about human fertility and population growth. Through the wonders of the internet, Academic Earth is offering a free (!) online course called Global Population Growth, given by Yale University professor Robert Wyman.
These views are the opinion of the author and do not necessarily either reflect or disagree with those of the DXS editorial team.
Today, Carolyn S. Miles, president and CEO at Save the Children writes at the Huffington Post (ducks) about the latest findings regarding our ability to stop a preterm birth from happening. As anyone who’s given birth knows, it’s not easy to stop that process once it starts, and that persistent inability means devastating outcomes for some families. As Miles writes:
One thing that cervical cancer awareness overlooks is that HPV causes not only that cancer but also can play a role in penile, vaginal, urethral, anal, and head and neck cancers. In fact, a recent study found that about 1 in 10 men and almost 4 in 100 women are orally infected with HPV, the most common sexually transmitted virus in the United States, and HPV-related head and neck cancer rates are higher among men. Further, HPV-related oral cancers have been on the rise for about two decades now, and HPV is now responsible for about 50% of oral cancers today.
Research also shows that about 50% of college age women acquire an HPV infection within four years of becoming sexually active. In addition, an infected mother can pass HPV to her baby during childbirth, and the virus can populate the child’s larynx, causing recurrent growths that block the respiratory tract and require surgical removal.
The remainder of this post appeared initially on the Parents of Kids with Infectious Diseasesite, which provides information for preventing infectious disease in addition to supporting parents whose children have them. As insidious as HPV is, the vast majority of HPV infections can be prevented now with a vaccine.
Have you or a loved one ever had an abnormal Pap test result? If precancerous cells were identified, the cause was almost undoubtedly infection with human papillomavirus (HPV).Almost all cases of cervical cancerarise because of infection with this virus. Yet a vaccine can prevent infection with the strains that most commonly cause cervical cancer.
A vaccine against cancer. It’s true.
For the vaccine to work, though, a woman must have it before HPV infects her. You may find it difficult to look at your daughter, especially a pre-teen daughter, and think of that scenario. But the fact is that even if your daughter avoids all sexual contact until, say, her wedding night, she can still contract HPV from her partner. As we noted above, it happens to bethe most common sexually transmitted infection.
About 20 million Americans have an HPV infection, and 6 million people become newly infected every year. Half of the people who are ever sexually active pick up an HPV infection in a lifetime. That means your daughter, even if she waits until her wedding night, has a 1 in 2 chance of contracting the virus. Unless it’s a strain that causes genital warts, HPV usually produces no symptoms, and the infected person doesn’t even know they’ve been infected.
Until the cancer shows up.
And it can show up in more places than the cervix. This virus, you see, favors a certain kind of tissue, one that happens to be present in several parts of you. This tissue, a type of epithelium, is a thin layer of the skin and mucous membranes. It’s available for viral invasion in the cervix, vagina, vulva, anus, and the mouth and pharynx. In fact, HPV is poised to replace tobacco as the major cause of oral cancers in the United States.
The virus can even sometimes pass from mother to child, causingrecurrent respiratory papillomatosis, the recurrent growths in the throat that must be removed periodically and can sometimes become cancerous. It strikes about 2000 children each year in the United States.
How does a virus cause cancer? To understand that, you must first understand cancer. You may know that cells reproduce by dividing, and that cancer occurs when cells divide out of control. Behind most cancers is a malfunction in the molecules that tell cells to stop dividing. These molecules operate in a chain reaction of signaling, like a series of well-timed stoplights along a boulevard. If one starts sending an inappropriate “go” signal or fails to send a “stop” signal, the cell divides, making more cells just like it that also lack the right signals. If your body’s immune system doesn’t halt this inappropriate growth, we call it cancer.
The blueprint for building these “stop” molecules is in your genes, in your DNA sequences. As a virus, HPV also requires a blueprint to make more viruses. Viruses use the division machinery of the host cell—in you—to achieve reproduction by stealthily inserting their own DNA blueprint into the host DNA.
Sometimes, when it’s finished with the host, a virus leaves a little bit of its DNA behind. If that leftover DNA is in the middle of the blueprint for a “stop” molecule, the cell won’t even notice. It will use the contaminated instructions to build a molecule, one that no longer functions in stopping cell division. The result can be cancer.
Of the 150 HPV types or strains, about 40 of which pass through sexual contact, two in particular are associated with cancer,types 16 and 18. They are the ones that may persist for years and eventually change the cellular blueprint. The vaccines developed against those two strains are, therefore, anti-cancer vaccines.
Without a successful viral infection, viral DNA can’t disrupt your DNA. That’s what the HPV vaccine achieves against the two strains responsible forabout 70% of cervical cancers. Recent high-profile people have made claims about negative effects of this vaccine, claims that have beenthoroughly debunked. The Centers for Disease Control and Prevention as always offersaccurate informationabout the side effects associated with available HPV vaccines.
This achievement against cancer, including prevention of almost 100% of precancerous cervical changes related to types 16 and 18, is important.
Worldwide, a half million women receive a cervical cancer diagnosis each year, and 250,000 women die from it. These women are somebody’s daughter, wife, sister, friend. Women from all kinds of backgrounds, with all kinds of sexual histories.
Women whose precancerous cervical changes are identified in time often still must undergo uncomfortable and sometimes painful procedures to get rid of the precancerous cells. These invasive procedures includecone biopsiesthat require shots to numb the cervix and removal of a chunk of tissue from it. Cone biopsies carry a risk of causing infertility or miscarriage or preterm delivery. A vaccine for your daughter could prevent it all.
HPV doesn’t care if your daughter has had sex before. It’s equally oblivious to whether the epithelium it infects is in the cervix or in the mouth or pharynx or in an adult or a child. What it does respond to is antibodies that a body makes in response to the vaccine stimulus.
Even if your daughter’s first and only sex partner passes along one of the cancer-associated strains, if she’s been vaccinated, her antibodies will take that virus out cold. It’s a straightforward prevention against a lifetime of worry—and a premature death.
For more info: Facts about theHPV vaccinefrom the National Cancer Institute.