Chapter 4C Apoptosis Flashcards
What is apoptosis?
Apoptosis is the natural and controlled death of cells within the body.
What triggers the mitochondrial (intrinsic) pathway of apoptosis?
Internal cell damage, such as mutated DNA, triggers the intrinsic pathway.
What are the two pathways of apoptosis?
The two pathways are:
Mitochondrial (intrinsic) pathway
Death receptor (extrinsic) pathway
What do both apoptosis pathways require?
Both pathways require a signal to initiate apoptosis and activate caspase enzymes.
Why do cells undergo apoptosis?
Cells undergo apoptosis when they malfunction, are damaged, or are no longer needed by the body.
What are caspases?
Caspases are death enzymes that trigger the breakdown of the cell during apoptosis.
What role do mitochondria play in the intrinsic pathway?
Mitochondria release cytochrome c into the cytosol when the cell is damaged.
What happens after cytochrome c is released?
Cytochrome c binds with intrinsic proteins to form an apoptosome.
What does the apoptosome do?
The apoptosome activates caspase enzymes, which initiate apoptosis.
What triggers the death receptor (extrinsic) pathway of apoptosis?
Death signaling molecules produced by immune cells trigger the extrinsic pathway.
Where do death signaling molecules bind?
They bind to death receptors on the cell membrane.
What happens when death signals bind to receptors?
The binding activates caspase enzymes, which initiate apoptosis.
What are the four stages of apoptosis?
The four stages are:
Activation of caspases
Digestion of cell contents
Cell shrinkage
Blebbing and formation of apoptotic bodies
What happens during the activation of caspases?
Mitochondria release cytochrome c when internal damage is detected, triggering caspase activation.
What happens during digestion of cell contents?
Caspases cut internal proteins (cytoskeleton) and break down organelles.
What happens during cell shrinkage?
The cell and nucleus shrink and collapse.
What happens during blebbing and formation of apoptotic bodies?
The cell membrane bulges, forming vesicles called apoptotic bodies that contain broken-down cell contents.
What happens after apoptosis?
Phagocytes (immune cells) engulf and digest apoptotic bodies through phagocytosis.
Why is apoptosis needed?
Apoptosis is needed for proper development
Examples:
The resorption of the tadpole tail
The formation of the fingers and toes of the fetus
The formation of the proper connections between neurons in the
brain
Why is apoptosis needed to destroy cells?
Apoptosis is needed to destroy cells
Examples:
Cells infected with viruses
Cells of the immune system once they are no longer needed (after infections)
Cells with DNA damage
Cancer cells
What is necrosis?
Necrosis is unregulated death of cells.
What can cause necrosis?
Necrosis can occur due to infection (by viruses & bacteria) or injury (physical damage such as cuts, burns, etc.).
What happens to a cell during necrosis?
The cell swells, bursts its membrane, and releases its contents into the surrounding tissues.
What is the result of necrosis?
The release of cellular contents causes inflammation, which is not seen with apoptosis.
