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Cell Biology

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Cell Biology is the study of biology on the molecular level.

In the last section we discussed how COVID-19 invades the cells in your airway.

But epithelial cells have a complex barrier called the cell membrane that typically prevents things from entering inside.

Cell membrane diagram depicting the complicated interplay of proteins, lipids, and carbohydrates (Source:
Cell membrane diagram depicting the complicated interplay of proteins, lipids, and carbohydrates (Source: ResearchGate).

Yet, somehow the virus is able to break this barrier and enter the cell. How does it do that?

Three Important Principles of Cell Biology

Principle 1: The Cell has a lot of Parts; But these Parts Work Together

In addition to the cell membrane, each (eukaryotic) cell has numerous components called organelles. Read important information about the organelles below:

Khan Academy article that breaks down the important organelles. This article was made for students preparing for the MCAT (medical school entrance exam).
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Learning hack #3: Go beyond memorization. For example, knowing that “the mitochondria is the powerhouse of the cell” is not good enough. A good way to go beyond memorization is ask, “what would happen to a cell if I removed the mitochondria?”.

Principle 2: Cells Get Energy through Cellular Respiration

One of the most important (yet pretty complicated) component of cells is their ability to create energy in the form of a molecule called ATP. Because there are a lot of moving parts, I recommend first watching a video to get a good overview of cellular respiration.

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Learning hack #4: Don’t get caught up in the details. Cellular respiration is a mechanism. You will likely encounter many mechanisms and systems in biology. It is easy to get caught up in making flash cards and trying to memorize every step. Don’t do that. First, understand the bigger picture of how energy is made. Then you can understand the specific steps.

Principle 3: Cells Can Use that Energy to Replicate

The final important concept is how cells can now use ATP to grow and even completely replicate.

Inside your body right now, billions of cells are probably in the process of replicating to help you grow and replace older cells. Interestingly, cancer is when your cells replicate out of control and start hurting your body.

Going back to the COVID-19 virus…

The virus does something kind of messed up: it binds to the ACE2 receptor on the cell membrane.

ACE2 is a protein on the cell membrane of airway epithelial cells that helps regulate our blood pressure by binding to a molecule called angiotensinogen. The spikes on the coronavirus have evolved to trick the ACE2 receptor that its angiotensinogen by having a shape that fits perfectly into the ACE2 receptor.

Now that the virus is inside the cell, it can manipulate the organelles in the cell. And eventually, it can hijack the DNA of the cell to create clones of the virus. This part will be discussed in the Genetics & Development section.

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