Apoptosis Flashcards
(19 cards)
What is apoptosis?
Apoptosis is a form of programmed cell death that plays a crucial role in maintaining tissue homeostasis and removing damaged or unnecessary cells.
What are the key pathways of apoptosis?
The key pathways of apoptosis are the intrinsic (mitochondrial) pathway and the extrinsic (death receptor) pathway.
What triggers the intrinsic (mitochondrial) pathway?
The intrinsic pathway is triggered by internal cellular stress such as DNA damage, oxidative stress, or growth factor deprivation.
What is mitochondrial outer membrane permeabilization (MOMP)?
MOMP involves Bcl-2 family proteins regulating mitochondrial membrane integrity, with pro-apoptotic proteins creating pores in the membrane.
What happens during the release of cytochrome c?
Cytochrome c is released from mitochondria into the cytosol.
What is the apoptosome?
The apoptosome is formed when cytochrome c binds to Apaf-1 and procaspase-9.
What is the role of caspase-9 in apoptosis?
Caspase-9 is activated by the apoptosome and in turn activates downstream executioner caspases such as caspase-3, -6, and -7.
What triggers the extrinsic (death receptor) pathway?
The extrinsic pathway is triggered by external signals via death receptors on the cell surface, such as Fas/CD95 and TNF receptor.
What occurs during ligand binding to death receptors?
Death ligands bind to their receptors, activating them.
What is the death-inducing signaling complex (DISC)?
The DISC is formed when receptor activation recruits adaptor proteins and procaspase-8 or -10.
What is the function of caspase-8?
Caspase-8 is activated by the DISC and can directly activate executioner caspases or amplify the signal through the mitochondrial pathway.
What activates initiator caspase-8?
DISC activates initiator caspase-8, which can directly activate executioner caspases or amplify the signal through the mitochondrial pathway by cleaving Bid to tBid, promoting MOMP.
What role does Bid play in apoptosis?
Bid, a pro-apoptotic Bcl-2 family protein, links the extrinsic and intrinsic pathways. Caspase-8 cleavage of Bid activates the mitochondrial pathway.
What are executioner caspases?
Executioner caspases (e.g., caspase-3, caspase-7) degrade cellular components.
What are the effects of executioner caspases on cellular substrates?
Executioner caspases cleave structural and regulatory proteins (e.g., lamin, PARP), leading to DNA fragmentation, cytoskeletal breakdown, and membrane blebbing.
What is phagocytosis in the context of apoptosis?
Apoptotic bodies express ‘eat-me’ signals, such as phosphatidylserine on the outer leaflet of the plasma membrane, attracting macrophages and neighboring cells to engulf them.
What are pro-apoptotic factors?
Pro-apoptotic factors include Bax, Bak, cytochrome c, and caspases.
What are anti-apoptotic factors?
Anti-apoptotic factors include Bcl-2, Bcl-xL, and inhibitors of apoptosis proteins (IAPs).
What determines whether a cell undergoes apoptosis?
The balance between pro-apoptotic and anti-apoptotic factors determines whether a cell undergoes apoptosis, ensuring controlled and non-inflammatory cell death.
