Video Transcript
The figure shows antibody proteins
in pale yellow binding to a surface protein of a COVID-19 coronavirus. How do these antibodies help the
body to fight the COVID-19 infection? (A) They chemically destroy the
virus protein coat directly. (B) They release antiviral
chemicals into the virus to stop replication. (C) They trigger natural killer
cells to attack the virus directly. (D) They stop the virus from
entering a host cell so it can no longer replicate. Or (E) they activate mast cells
that stimulate an inflammatory response.
To answer this question, we will
need to review how antibodies help the body to fight the virus that causes COVID-19
in humans. Let’s remove our answer choices for
now so we’ve got a bit more space to figure this out.
You might already know that
antibody therapy and vaccines are becoming very useful to combat COVID-19. So, let’s discuss antibody
structure and their function in the adaptive immune system, before taking a look
back at our answer choices to figure out which one is correct.
An antibody is usually depicted as
a Y-shaped molecule, which you might have noticed in the image provided by the
question. By looking at a simplified image of
an antibody that shows this Y shape more clearly, we can see that the tips of the Y
contain specific antigen-binding sites. Antibodies with specific
antigen-binding sites are developed in response to foreign invaders in our bodies,
such as viruses, and are stored in the lymph organs from which they can be secreted
to combat any additional attacks. This is how resistance to viruses
such as COVID-19 is obtained.
Our question asks us about the
antibodies that are produced against the virus that causes COVID-19. In our diagram, we can see that the
antibodies are binding to the surface or spike proteins of the coronavirus. Because this spike protein is
implicated in viral entry into our own cells, which are sometimes called host cells,
the antibodies will disrupt this process. Remember that viruses must be able
to enter host cells in order to replicate and continue reinfection, so antibodies
can prevent this.
Let’s bring back or answer choices,
as now we have enough information to answer our question. The way that these antibodies help
the body to fight the COVID-19 infection is answer choice (D). They stop the virus from entering a
host cell so it can no longer replicate.
