The Handy Chemistry Answer Book (2014)

Many of the questions in this chapter were submitted by undergraduate students from around the country. We’ve listed all of their names in the Acknowledgement section at the beginning of the book. We want to thank them again for submitting such interesting questions, and if you have questions about chemistry that you’d like to see answered, please send them to us!

MEDICINE AND DRUGS

How does Viagra® work?

Viagra^® (Sildenafil) interferes with an enzyme located in the erectile tissue that breaks down a molecule called cGMP (cyclic gunaosine monophosphate). Viagra® slows down this enzyme, allowing the amount of cGMP to build up. cGMP is responsible for a process known as vasodilation, or widening of the blood vessels in smooth muscle cells. More blood in these vessels means a stronger erection.

How does my ADHD medication work?

Ritalin® (Methylphenidate) is probably the most common drug for the treatment of ADHD (attention-deficit hyperactivity disorder). Ritalin® is a stimulant, increasing the levels of dopamine in your brain. Your brain normally releases dopamine to communicate feelings of pleasure and to increase the rate at which your neurons fire, which is supposed to help you focus.

How do painkillers know what part of the body to target?

Or phrased another way—why doesn’t your whole body get a little numb when you take a painkiller? Let’s limit this discussion to what are called nonsteroidal drugs, like ibuprofen. Ibuprofen, and other drugs like it, work by interrupting the series of signals that your body uses to communicate pain to your brain. The COX (cyclooxygenase) family of enzymes play an important, but intermediate, role in this pathway. This means that the COX enzymes take one type of signal and convert it into another that your body recognizes as pain. By working on an intermediate messenger, ibuprofen only takes effect where the pain is occurring—that first signal has to already be there—so your whole body doesn’t get numb when you take ibuprofen.

What’s the difference between acetaminophen and ibuprofen?

While the structure of acetaminophen and ibuprofen are very different, the mode of action is similar. Both of these painkillers interfere with the COX family of enzymes we just talked about. Ibuprofen interacts more broadly with members of this family of enzymes, which ends up making it a good painkiller as well as a good antiinflammatory medication. Acetaminophen binds primarily to one of the members of this family (COX–2), so it’s basically just a painkiller.

Why do some prescription pills come in such elaborate colors/capsules?

There’s no chemical reason for this. Sometimes pills are colored for branding purposes—Pepto-Bismol® is pink, Viagra® is blue, Cymbalta® is green—and you recognize those colors. It can also help people keep track of which pill is which, and also to remember which ones to take.

How does cold medication work?

Unfortunately, doctors and scientists still have not found a cure for the common cold! Cold medicines work by trying to minimize the symptoms of a cold while your body is busy fighting the virus that caused it in the first place. Some medicines, like those you buy at your local drugstore, work by using antihistamines, pain medicines, and decongestants to help relieve symptoms. These include all of the things you typically associate with a cold: a runny nose, a scratchy throat, sneezing, and dry or itchy eyes. Other cold remedies try to help strengthen or support your body’s immune system while it fights the cold. These include vitamins (often vitamin C), zinc supplements, and echinacea. You shouldn’t expect these to bring immediate relief to your symptoms as you would with over-the-counter medications, though.

What is echinacea?

Echinacea is a group of flowers, related to daisies, sometimes also called coneflowers. Different members of this group are used in herbal medicines to stimulate the body’s immune system. Scientific studies on the effectiveness of echinacea are contradictory, however, as some have shown clear effects in the prevention of or shortening of the length of colds, while others have concluded that it is mostly ineffective.

What is typically analyzed when a doctor takes your blood sample?

There are actually several types of blood tests that your doctor may perform, depending on your symptoms and what they are looking for. These include tests to look at your blood chemistry, the enzymes present in your blood, tests of how well your blood is able to form a clot, tests to assess risk for heart disease, or a complete blood count. A complete blood count can detect the presence of many diseases and immune system disorders by measuring the numbers of red and white blood cells, platelets (blood cell fragments that promote clotting), hemoglobin (the protein that carries oxygen), hematocrit (the amount of space taken up by red blood cells), and mean corpuscular volume (a measure of the size of red blood cells).

Blood chemistry tests provide information about the health of your muscles, bones, and organs. This test reports blood glucose, calcium, and electrolyte levels. It will also test the function of your kidneys. This is often a test that requires you to not eat any food for some length of time before the test so that the doctor can get an accurate measure of your blood chemistry that is not influenced too heavily by what you have eaten recently.

Blood tests to assess heart disease focus on measuring your cholesterol levels. This includes low-density lipoproteins (LDLs, often called “bad” cholesterol), high-density lipoproteins (HDLs, often called “good” cholesterol), and triglycerides (a type of fat). This test also typically requires you to not eat for about half a day prior to having your blood taken, as your cholesterol levels can be easily influenced by what you have recently had to eat.

While blood tests typically cannot diagnose diseases themselves, they can provide a strong indication of what disease(s) you may have and direct your physician to provide other tests that can confirm a diagnosis.

What chemicals are typically analyzed in a urine analysis?

Just like a blood analysis, there are several analytes that can be looked at by urine analysis: pH, density, proteins, glucose, ketones, leukocytes, blood, or human chorionic gonadotropin (the presence of which can indicate pregnancy).

The results can indicate several things about a person’s health. If the person is well-hydrated, for example, a lower density would be expected. The presence of proteins in the urine is uncommon, and this may indicate that the patient’s kidneys are not functioning properly. Similarly, glucose and ketones should not be present in the urine, but if they are, their presence could be a symptom of diabetes.

Can cold weather really cause a cold?

This actually is not true! Colds are caused by a virus that must enter your body to cause cold symptoms. Contracting the cold virus really has nothing (directly) to do with cold weather. The only reason colds seem to be more prevalent during colder seasons is that people spend more time indoors, placing them in closer proximity to one another, which makes it easier for the virus to spread between people.

Why does drinking alcohol make people loopy?

Alcohol, specifically ethanol (CH₃CH₂OH), is a mild depressant that affects your central nervous system. The specific biological effects are pretty complicated—some systems are enhanced by ethanol, others are inhibited. This combination of effects is why drinking can relax your muscles but also make you more animated. It may seem that alcohol lowers your inhibitions, but some experiments suggest this is a psychological effect and not a chemical one.

Can cracking your knuckles really lead to arthritis?

No. In your joints there is a liquid called synovial fluid, which serves as a lubricant. When you cause your knuckles to crack the synovial fluid has to fill more space, and this is what causes your knuckles to make a cracking noise. Arthritis comes about when your immune system starts to cause harm to your joints. Of course, cracking your knuckles too much can still cause other problems for your joints, just not arthritis.

How does your liver process alcohol?

The liver contains an enzyme called alcohol dehydrogenase, which is responsible for metabolizing ethanol. Alcohol dehydrogenase converts the ethanol to another molecule called acetaldehyde, which is then excreted from the body. A healthy liver can process about half an ounce of pure ethanol each hour, which equates to roughly one beer, one glass of wine, or an ounce of liquor each hour.

What happens chemically that causes a hangover?

Hangovers are believed to be caused by the buildup of acetaldehyde. This aldehyde is formed from the oxidation of ethanol, which is of course the “alcohol” you drank in the first place. Acetaldehyde is an intermediate in your body’s process for dealing with all that booze you drank last night. An enzyme, acetaldehyde dehydrogenase, further oxidizes acetaldehyde to acetic acid.

Of course there are a lot of other factors that might make you feel terrible the morning after a big night out. Your liver gets pretty taxed dealing with all of the toxins, which is why some people think that distilled alcohol (which removes heavier molecules in the alcoholic beverage) leads to less severe hangovers.

Is it true that coffee can help you to sober up faster?

Unfortunately, no. Intoxication is related to the amount of alcohol (ethanol) in your body, and the quantity of alcohol will only decrease as your liver works to metabolize the liquor. Drinking caffeine won’t really do much to accelerate your liver function, so coffee cannot, in fact, sober you up. It may help you to stay more awake or alert, but you’ll still be intoxicated.

Does putting urine on a jellyfish sting really help?

You may have heard of this before, but it seems that it may just be an old wives’ tale. Washing the area of the sting with saltwater is recommended so as to deactivate any of the stinging cells from the jellyfish that may be present on your own skin. Fresh water may actually reactivate the cells that caused the sting, causing you further pain.

Does eating chocolate or fried food cause acne?

No. Acne is caused by oil glands in a person’s skin over-producing an oil called sebum, which is what the body naturally uses to keep skin lubricated. If this excess oil, along with dead skin cells, blocks your pores, then your skin can become irritated and a pimple may form. While the causes of excess sebum production are not definitively established, there is no reason to think that chocolate or fried foods are at fault.

A common myth is that eating some foods, such as chocolate, causes acne. Pimples are actually caused by a build up of sebum, but why this happens is not clearly understood.

What causes dandruff?

Despite what you may have heard, dandruff is actually not caused by dry skin but rather by a specific type of fungus or yeast. While dandruff does cause flaky scales of skin to shed off of the top of a person’s head, dandruff is actually due to the interplay between yeast organisms and natural oil glands. Unfortunately there is no genuine cure for dandruff, but it can be controlled by using special shampoos containing zinc pyrithione, selenium sulfide, coal tar, or ketoconazole. To be effective, these products typically need to remain on the skin for several minutes before being washed away. In fact, the scalp is not the only place that dandruff can occur! Dandruff can also manifest on a person’s eyebrows, mustache, and beard area, as well as the ears and the nose.

Can wearing a copper bracelet help with the symptoms of arthritis?

Arthritis is caused by deterioration of the cartilage in a person’s joints, where deterioration happens faster than the body is able to repair it. Copper bracelets are sold based on the idea that a person may have a copper deficiency that leads to the pain in their joints, thus implying that copper from the bracelet could be absorbed through the skin to help correct the deficiency. In fact, copper deficiencies are extremely rare, and most people eat plenty of copper in their regular diet. Rarely are additional copper supplements necessary. It has not been proven that copper can be absorbed through the skin, nor has it been proven that the bracelets can help with any symptoms of arthritis or joint pain.

Moreover, excess intake of copper can result in poisoning, so if copper can be absorbed through the skin from a bracelet, one would want to monitor their dosage carefully. It is also worth pointing out that we know of no cases of poisoning resulting from wearing copper bracelets.

Can eating carrots help your eyesight?

It does seem likely that carrots help your eyesight, so it’s not a myth! Carrots, and other colorful vegetables, tend to have a lot of vitamin A, and vitamin A helps the retina to stay healthy and working well. This is because it helps to generate rhodopsin, which is a light-sensing molecule located in the retina. Developing a deficiency of vitamin A can actually lead to night blindness!

Unlike the myth about chocolate causing acne, carrots actually do help your eyesight because they contain a lot of vitamin A, which is important for the health of your retinas.

Does spinach provide a good source of dietary iron?

Spinach has the same dietary content as many other green vegetables. However, spinach additionally contains oxalic acid, which actually prevents iron from being absorbed by the body! Thus it may actually be a worse source of iron than other foods. An interesting anecdote: The iron content of spinach was initially reported to be about ten times higher than it actually is, all due only to a misplaced decimal point. Spinach does contain plenty of good antioxidants and vitamins, though, so we don’t mean to suggest you should stop eating it. It’s just that if you heard it was an exceptionally great source of iron, you may have been misled by the original mixup over how much iron is actually present in this vegetable.

Will you contract poison ivy if you come into contact with a person who has it?

Poison ivy is caused be a an oil called urushiol, found on the leaves of poison ivy plants. The only way to contract poison ivy is to come into contact with this oil. Thus, if a person who has poison ivy still has some of the oil from the plant present on their skin, they could spread that oil to another person. In most cases, though, by the time a person has a rash, the oil will have been washed away. To be clear, the blisters on a person’s skin who is suffering from a poison ivy rash do not themselves have the potential to spread poison ivy to other people.