The 2020 Spring Festival has given us too much to catch off guard, and the root of all of this is related to the emerging virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
The 2020 Spring Festival has given us too
much to catch off guard, and the root of all of this is related to the emerging
virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Why a small virus has such great power, in
order to understand its function, you need to start by understanding its
structure, after all, the structure determines the function.
I. New Crown Structure
First, we need to know that the name of the
virus is SARS-CoV-2. This new coronavirus belongs to the same coronavirus as
SRAS.
Coronaviruses are named after the obvious
stick-shaped particle bulges that can be observed under a microscope, which
resemble the crowns of European medieval kings.
Next, look
closely at the structure of the virus from the outside to the inside. There are
three kinds of proteins in the outermost layer of coronavirus, which are called
spike glycoprotein, small envelope glycoprotein (M protein), and membrane
glycoprotein (E-protein).
Spike
glycoprotein mainly recognizes and binds to host cell surface receptors and
plays a key role in mediating the fusion of the viral envelope and cell membrane.
In layman's terms, spike glycoprotein acts like a key, and its main function is
to open the cell membrane of the host cell.
Immediately
afterward, the envelope on the surface of the virus is also called the
capsule, which is mainly a lipid component, which is similar to the principle
of the lipid bilayer of human cell membranes and the similarity of the chemical
compatibility. cell.
Finally,
entering the inside of the cell, there is an RNA with a single-stranded
structure. As RNA has no double-stranded structure and does not have the error-correcting ability that can match the DNA, the new crown virus is more
likely to mutate.
To be clear,
this RNA structure provides the structural basis for RT-PCR, the “gold
standard” for the detection of new coronary pneumonia.
II. The Process of the Virus Attacking the Human Body
After
completing the structural observation of our enemies, we may wish to take a closer look at a virus raid in a local battle.
First, we
need to make clear that the virus cannot survive on its own, that is, it must
parasitize other host cells.
When a
virus parasites a cell, it usually goes through four steps: adsorption and
entry, husking, biosynthesis, assembly, and exocytosis.
1. Adsorption and Infiltration:
When the virus enters the adjacent position of the
alveoli through the respiratory tract, the virus specifically bind to the door
locks of certain cells, such as ACE2 receptors, by using the spinous protein as
a key, thereby cleverly deceiving the cells and opening the portal. The lipid
envelope quickly passes through the lipid bilayer and enters the host cell.
Compared
with other organs, human airway ciliary cells, and alveolar epithelial cells
have higher levels of ACE2 protein, which explains why the new crown virus
first chose the lungs to attack.
2. Unshelling:
After the virus enters the cell, the virus will attract the cell
factory picket team-lysosome to inactivate it by its own coat-protein core
capsid. This step is called "unshelling".
Because of
this, the virus's genetic material, RNA, is completely exposed inside the cell.
Of course, it will not just be satisfied with this.
3. Synthesis:
When the genetic material RNA has invaded the cell's synthesis
workshop-ribosomes, the virus finally began its wanton reproduction. This step
"synthesis" focuses on re-producing the important parts needed for
the virus, so it will be mapped again To our previous description of the
structure of the virus:
- First, one-way positive-stranded RNA directs the synthesis of a number of viral-related proteins, including nucleocapsid proteins.
- Second, one-way positive-stranded RNA is transcribed into negative-stranded RNA by using itself as a template, which in turn generates new progeny positive-stranded RNA. This process is repeated, and a large amount of new RNA is obtained.
- Thirdly, after the negative-strand RNA is selectively converted into a fragment of the positive-strand RNA, various small proteins can be specifically synthesized.
4. Assembling and Exporting:
So far we have obtained three main parts, and we can
complete the core assembly. According to some theories, lipid envelopes are
mainly obtained when the exocytosis passes through the endoplasmic reticulum or the cell membrane and the lipid membrane components are obtained.
So far, the virus has completed the entire process of replication.
What will
happen to its fate? Whether it is a long-term incubation or waiting for an opportunity, this involves the outcome of the virus. It can choose to passively
increase as the cell replicates, or it can reproduce in large numbers, causing
direct toxic killing and resource invasion to the cell.
The last question is for you. If you are a virus, what choice will you make in order to
maximize the benefits of your cluster?
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