What is Apoptosis?

Apoptosis, also known as programmed cell death, occurs when a cell discovers a flaw in its genetic code and destroys itself in a way that doesn’t harm any of the cells around it and allows its organelles to be reabsorbed by its neighbors.

The Process of Apoptosis

Apoptosis begins when the cell recognizes a disturbance in its genetic code through the use of caspases (tumor suppressor proteins). The tumor suppressor proteins, most commonly p53, registers a problem in the cell and signals to begin repairing damages. Once the damage is too severe and the cell can no longer fix itself, p53 initiates apoptosis.

(AssayGenie)

Shrinkage

The first chemically initiated step of apoptosis is cell shrinkage. The cell membrane will shrink down and compact the organelles. At this step the nucleus breaks down its DNA into small pieces that aren't harmful

Membrane Blebbing

Membrane blebbing is when the cytoskeleton of the cell breaks up and puts pressure on the cell membrane, this causes the membrane to bulge outward.

Apoptotic Bodies

After blebbing occurs the blebs will start to break off into apoptotic bodies. These bodies carry organelles and pieces of the cytoskeleton, they are completely contained in the membrane to prevent any damaged DNA from entering other cells.

Phagocytosis

Phagocytosis occurs when white blood cells, most commonly macrophages or phagocytes absorb and destroy the apoptotic bodies. While it is uncommon, during this step healthy cells can absorb healthy apoptotic bodies to use their organelles or proteins.

Why is Apoptosis Important?

Apoptosis is vital for cellular regeneration and formation throughout every stage of our lives'. Our skin is constantly changing, with cell turnover happening every 28-30 days, this can't happen without apoptosis. As the deeper layers of the epidermis move to the surface, the cells at the surface layer will perform apoptosis to make way for new, healthy cells. This also happens in many cases in utero, the most common example of this is when a fetus is around 7-8 weeks. Before this, the fetus has paddle-like webbed hands, at 7-8 weeks apoptosis is initiated to destroy the cells that make up the webbing.

However, the most important function of apoptosis is for tumor suppression. When the damaged DNA is discovered by the cell, the cell will hit "the self destruct button" and destroy the DNA before it can cause mutations in the neighboring cells and cause a tumor.

Apoptosis vs Cell Necrosis

What's the difference?

(AAT Bioquest)

Apoptosis and cell necrosis are two different types of cell death. Apoptosis, as explained above, is programmed cell death. This occurs when there is a malfunction in the cell's genetic code, the cell will process this and destroy itself in a way that allows the cells around it to utilize the organelles and proteins found inside the apoptotic bodies. Cell necrosis is cell death that is not quite as clean as apoptosis. Caused by acute cellular injury, necrosis causes the cell to bleb similarly to apoptosis but then it will rupture and cause inflammation.