Apoptosis Flashcards
What is apoptosis?
Apoptosis is programmed cell death, which is crucial for development, tissue homeostasis, and cancer defense. It involves cell shrinkage, DNA condensation, and fragmentation.
What can happen when apoptosis fails?
Failure of apoptosis can cause issues like fused fingers/toes due to unregulated cell growth, and DNA-damaged cells may survive, leading to cancer.
What are the two main types of caspases?
Initiator caspases (e.g., Caspase 8, 9) start apoptosis by activating executioner caspases (e.g., Caspase 3), which carry out cell death.
What are the visible signs of apoptosis in a cell?
Apoptotic cells are smaller, have membrane blebbing, and show chromatin condensation and nuclear fragmentation.
How does apoptosis differ from necrosis?
Necrosis is uncontrolled cell death, causing swelling, membrane rupture, and inflammation. Apoptosis is regulated and does not cause inflammation, involving cell shrinkage and DNA fragmentation.
What is the “Eat Me” signal in apoptosis?
The “Eat Me” signal involves the exposure of phosphatidylserine on the apoptotic cell’s surface, which is recognized by phagocytic cells like macrophages, leading to engulfment.
What are caspases in apoptosis?
Caspases are proteases that drive apoptosis by cleaving target proteins. They exist as inactive procaspases and become active after cleavage.
What is the extrinsic pathway of apoptosis?
The extrinsic pathway is activated by ligand binding (e.g., TNF-α or Fas ligand), leading to caspase activation and cell death.
What role does cytochrome c play in apoptosis?
Cytochrome c is released from mitochondria and binds to Apaf-1, leading to the formation of the apoptosome, which activates caspases and drives apoptosis.
What is the intrinsic pathway of apoptosis?
The intrinsic pathway is triggered by mitochondrial damage, leading to the release of cytochrome c, activation of initiator caspase 9, and cell death.
How is apoptosis regulated by Bcl2 family proteins?
Bcl2 family proteins regulate apoptosis by controlling mitochondrial permeability. Bcl2 is anti-apoptotic, while BH123 and BH3-only proteins are pro-apoptotic.
What is the role of p53 in apoptosis?
P53 promotes apoptosis by inducing the expression of pro-apoptotic genes like Bax, Bak, and Fas-R, leading to cytochrome c release and activation of cell death pathways.
What is the role of Akt kinase in apoptosis?
Akt kinase, activated by survival signals, phosphorylates Bad, preventing Bad from inhibiting Bcl2, thus preventing apoptosis.
How does Bcl2 inhibit apoptosis?
Bcl2 prevents the aggregation of BH123 proteins, stopping the release of cytochrome c from mitochondria, thus blocking apoptosis.
What happens if there is too much or too little apoptosis?
Too much apoptosis can lead to diseases like AIDS, Parkinson’s, and Alzheimer’s. Too little apoptosis can contribute to cancer.
