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Apoptosis vs. Autophagy

Instructor: Artem Cheprasov
This lesson goes over two different processes. First, you'll learn what apoptosis means and why it occurs and then what autophagy refers to and why it occurs as well.

Dinner or Death?

Dinner or death? Which would you choose? Probably dinner. The cells of your body choose dinner over your death as well. Actually, the cells of your body choose their own death over your death too! How so? Well, you'll find out as you learn about apoptosis vs. autophagy in this lesson.

Apoptosis

Let's start with cell death.

Apoptosis, historically referred to as necrobiosis or single cell necrosis, is commonly called cell suicide. In other words, the cell carefully and deliberately 'programs' and executes its own death. Thus, apoptosis is also known as programmed cell death.

The term apoptosis comes to us from the Greek prefix 'apo-', which refers to the separation of something and the suffix '-ptosis', which refers to 'falling off'. As in, the falling off of leaves from a tree or petals from a flower. However, in our case, the term apoptosis is generally used with respect to a couple of things:

1. The fact that an apoptotic cell can break apart into smaller segments that give it the appearance of falling apart like a flower.

2. The fact that apoptotic cells essentially leave an empty space behind where they once were. Sort of like a leaf dropping out from a field of leaves on a tree and leaving an empty space.

Note how the cell appears to fall apart during apoptosis.
Apoptosis

Apoptosis is a very carefully controlled process of cell death. This should be contrasted with necrosis, which is a very messy process involving cell death. Apoptosis occurs for numerous reasons. Sometimes, it's a process of normal tissue development. Other times, the cell may commit suicide in order to save the body. For instance, if the cell recognizes it's becoming cancerous, it may self-destruct.

Autophagy

OK. Now let's move on to dinner and see what it has to do with death.

Autophagy refers to a process where a cell degrades its own cytoplasmic material. Meaning, the cell degrades its internal contents. Autophagy comes from 'auto-', self, and '-phagy', eating. So the cell is literally eating itself in autophagy. This digestive process occurs in what is sometimes referred to as a cell's 'stomach', the lysosome.

The lysosome can devour whatever must be, including improperly folded proteins, infectious organisms inside the cell, mitochondria, damaged internal organelles, and much more.

It does so through one of three major ways:

1. The lysosome can merge with a balloon-like structure, called a vesicle, which contains whatever needs to be digested. This is known as macro-autophagy.

2. The lysosome can invaginate, or pull into itself, whatever it wants to eat on its own. This is known as micro-autophagy.

3. The lysosome can use chaperone proteins to guide other proteins across the lysosomal membrane and into the lysosome itself for digestion and destruction. This is known as chaperone-mediated autophagy.

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