Hey it's professor Dave, let's learn about pharmaceuticals.
We all get sick from time to time. Whether it's just a cold, or
something more serious, and there's great controversy amongst the public about how
to treat disease.
Some argue that conventional medicine is best suited to address the health needs
of the human body, while others are skeptical, avoiding the entire system in
favor of some kind of alternative. But before anyone discredits Western
medicine, they must understand that all disease has a molecular basis. Whether
the cause is bacterial infection, a genetic mutation, or anything else, any
proposed treatment that does not address this fundamental cause for the disease
is very unlikely to have any merit. So let's examine a few types of diseases
and the methods that science has come up with to combat them, which we can refer
to as drugs. One category of disease is genetic disorder.
These can be hereditary, passed down from parent to offspring or they can be the
result of a mutation sustained during a person's lifetime.
These will always involve some change to DNA that affects the product of gene
expression, resulting in a protein with behavior that deviates from what is
normal. If we need to shut down a particular biochemical process that has
gone awry, one solution that we have stumbled upon in science is the concept
of an inhibitor. We know that there are enzymes and receptors that mediate so
much of what goes on in the cell, and sometimes we may need to silence one of
these. An inhibitor is a molecule that will fit into the active site of, say, an
enzyme, and bind either reversibly through electrostatic interactions or
more permanently through covalent bonds, such that the normal substrate is unable
to enter. This kind of inhibition, called competitive inhibition, prevents the
substrate from coordinating and therefore also prevents the enzyme from
performing its function. There is also noncompetitive inhibition, where a
compound binds to the enzyme in some other location and causes a
conformational change that decreases the active site's affinity for the substrate.
This also disrupts enzymatic function. Many poisons work this way, and are
dangerous because of the important cellular processes they inhibit. But when
an irregular cellular process is doing harm to the organism, an inhibitor can
stop this activity. Inhibitors are therefore a huge part of the
pharmaceutical industry. We have to recognize that if a disease such as some
form of cancer is the direct result of a genetic mutation and results in either
a misbehaving or non-functional protein, then that is the fundamental
cause of the disease. Any potential solution or cure must specifically
address that cause, by somehow inhibiting the expression of that gene,
inhibiting the resulting protein, or some other similar biochemical strategy.
When the cause is this specific, there is nothing about diet or exercise that can
have any impact whatsoever, since your general health, as important as it is,
is not linked to the highly specific origin of such a disease. That's why skepticism
towards the pharmaceutical industry, which can certainly be legitimate from a
social or economic standpoint, if misplaced onto the science itself, can
have disastrous consequences on the health of an individual or an entire
population. Another application for inhibitors can be found in the domain of
mental health. We learned about neurotransmitters, and it is the case
that molecules like serotonin, dopamine, and norepinephrine will dictate your
mood by transmitting signals through the synaptic cleft. If these
neurotransmitters exist in insufficient concentrations, it can lead to depression.
One solution to this problem is to use a reuptake inhibitor. This is a molecule
that blocks the receptors that reabsorb some of the neurotransmitter molecules
which results in a greater
concentration of neurotransmitters in the synaptic space, and therefore more
effective transmission. Once again, the fundamental cause of the problem is that
not enough of a particular molecule is being transmitted, so a drug that
addresses that problem by increasing the transmission of that molecule one way or
another is going to be best suited for solving that issue. In this way, those who
criticize antidepressants as being merely a chemical solution to a deeper
problem are not fully aware of the specific chemical nature of the problem
in the first place.
This does not mean psychotropic drugs are the solution for every mental health
issue, but they can be very successful for certain people. Some diseases are the
result of some kind of deficiency in an essential vitamin or mineral.
Take vitamin C, for example. As we now understand, this molecule, also called
L-ascorbic acid, acts as a coenzyme in certain enzymatic pathways, such as
collagen synthesis. Collagen, a structural protein present in connective tissue, is
the most abundant protein in the human body, and vitamin C is needed to activate
the enzyme that performs one of the steps in synthesizing collagen. If we do
not consume enough vitamin C, collagen synthesis is impaired and we get scurvy,
like a pirate on the high seas.
The reason this would happen is that vitamin C is predominantly found in
fruits and vegetables, and these tend to spoil during a long journey. A vitamin is
therefore just a molecule that we need to ingest for proper cellular function
because we can no longer synthesize it ourselves, as the ability was lost
somewhere over the course of biological evolution. But plants still make all
these nutrients, so as long as we eat the plants we will be just fine.
The amazing feat of modern chemistry is to recognize the link between a disease
like scurvy and a molecule like ascorbic acid, and furthermore to know the
structure of this molecule such that we can build it ourselves, and
offer it in the form of supplements to those who do not have access to the
whole foods that contain them.
Contrary to popular belief, there can be absolutely no difference between a
molecule of ascorbic acid found in a fruit and one made in a lab, because they
are identical arrangements of precisely the same atoms. It is the shape of a
molecule that causes its bioactivity, not its source. Another category of disease
is the pathogenic. A pathogen is any microorganisms that can cause disease
like bacteria or viruses. Most bacteria are harmless or even beneficial to the
human body, but there are some that cause infectious diseases, like tuberculosis or pneumonia.
It was not that long ago that we were completely unaware that these organisms
even existed. But once we realized that they were responsible for certain
diseases, our studies of these organisms led to the invention of antibiotics,
which can kill certain bacteria. Many of these operate on the basis of a
difference between bacterial cell structure and human cell structure.
Bacterial cells possess a cell wall made of a substance called peptidoglycan,
which human cells do not possess. The first antibiotic ever discovered,
penicillin, inhibits a bacterial enzyme that is used to regenerate the cell wall.
So in the presence of the drug the cell wall of bacterial cells will rupture,
spilling their contents and thus killing the bacteria. Antibiotics like penicillin
and others that followed have almost single-handedly doubled the human
lifespan. Viruses, however, have different structures and mechanisms of survival
from bacterial cells, as viruses are not cells at all, they are much tinier and
operate by inserting their genetic material into a host cell, hijacking the
cellular machinery, and forcing it to generate more viruses, while typically
destroying the cell in the process. Thus, antibiotics do not work on viruses.
Instead, vaccines have proven effective in training the human body to prepare
a response to certain types of viruses by introducing a piece of the virus so
that the immune system can recognize and remember it for optimal future response.
This is how we have largely eradicated many diseases like smallpox, polio, and measles.
However, again, skepticism of vaccination threatens to facilitate the return of
some of these diseases. For other viruses a more complex approach is required, but
any legitimate antiviral drug will disarm some biochemical process that the
virus relies on. For example, in order to invade a host cell, receptors on the
virus must recognize certain receptors on the cell. If inhibitors are introduced
that block either of these receptors, the virus will not be able to enter and
reproduce. Other drugs can inhibit the transcription of viral DNA once it is
inside the cell. And ribozymes are specially designed enzymes that can
target viral DNA and chop it up so it can't be transcribed. Whatever the case
may be, any legitimate treatment must be preceded by a sophisticated knowledge of
the biochemistry involved.
By contrast, some diseases are strictly physiological, like many forms of
cardiovascular disease. These involve the heart or blood vessels and can occur
because of poor diet, lack of exercise, or other lifestyle factors. These are the
ones in which a holistic approach to general health can be effective in
preventing, but there are also medications that offer some assistance.
All of these systems will be covered in greater detail in the upcoming biology series.
So we must understand that in order to treat a disease, it is
imperative that we understand how it operates on the cellular and molecular
level, and then come up with a strategy that addresses some detail on one of
these levels. That is the approach of pharmaceutical drugs, which are specially
designed molecules that can inhibit specific biochemical processes.
This allows us to eliminate pathogens, silence mutant enzymes, and more. If by
blind chance an
ancient tradition has discovered a food or plant that has legitimate medicinal
properties, which is certainly possible since humans have been curious and bold
enough to try things far before we understood chemistry, that substance has
those medicinal properties because it contains an active ingredient, some
molecule inside it that performs a biochemical function similar to the
strategies we have discussed, not because the plant as a whole is sacred or magic.
Everything in your body is made of molecules, and every biological process
involves the interaction of those molecules. Unfortunately, most people do
not have a background in chemistry and biochemistry
so when trying to make assessments about health and medical treatment they must
simply go by what they have heard. But there is a lot of misinformation out
there, whether it is genuine misunderstanding or deliberate
manipulation for financial gain. A vilification of Western medicine is a
popular meme that leads people away from legitimate medical treatment, as they
instead opt for alternative medicines with no real impact other than a placebo
effect, which can be enough to cure your headache, but will never cure your cancer.
Luckily, as you continue to build your understanding of science, you won't be so
easily manipulated.
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