Cells Alive 6: Cell Death Flashcards
Necrosis
Non-Programmed cell death, non-physiological process
Apoptosis
Programmed Cell Death, Homeostatic mechanism, can also occur as a defence mechanism
Autophagy
Survival mechanism that can lead to cell death
What causes Necrosis?
Accidental death following an injury such as trauma or lack of blood supply, the cells burst and the release of cell content causes inflammation
How does apoptosis occur?
by the process of phagocytosis, it is controlled and there is no inflammation
What proteins break down the cells in apoptosis?
Caspases
How does the extrinsic pathway of apoptosis work?
Death receptor binds to death ligand, this triggers the activation of caspases and proteins that form the disc complex, caspase 8 triggers caspase 3, 6 and 7
What is DISC?
death inducing signalling complex
What is the intrinsic pathway of apoptosis?
Signalling/ Trigger occurs from inside the cell, e.g. radiation or toxins to activate caspases
What is a negative signal?
Absence of growth factors or hormones or any factor that supresses apoptosis
What is a positive signal?
Radiation, Toxins Viral infection (not receptor-mediated)
What does cytochrome C mediate?
The production of cast base 9
What is Autophagy?
Cell self-eating process, induced by starvation- it degrades cytplamsic constituents and organelles in the lysosome
What is an example of apoptosis?
Removal of a tadpoles tail to become a frog
What is the purpose of apoptosis?
To destroy cells that represent a threat to the entirety of the organism, e.g cells infected with viruses, cells with DNA damage and potentially cancer cells
What do initiator caspases activate
a cascade that activates effector caspases
What do effector caspases do?
Cleave cellular components, such as the nuclear lamina, activate DNAses and other structural proteins
What are some negative signals that trigger the intrinsic pathway?
absence of growth factors/ hormones, loss of factors that usually suppress apoptosis
What are some positive signals that trigger the intrinsic pathway?
Radiation, Toxins, hypoxia
Changes in mitochondrial membrane
2) Opening of the MPT pore
3) Release in the cytoplasm if mitochondrial proteins (e.g. cyt C)
4) Binding of Cyt C to pro-caspase 9 leading to its activation
What modulates the events of the intrinsic pathway?
- Bcl2, Bcl-X-anti-apoptotic
- Bax, Bid, Bad-pro-apoptotic
They regulate the release of Cyt C from the mitochondria
What caspase does the intrinsic pathway activate?
Caspase 9
How is autophagy different to apoptosis?
Has markers, ULK, Beclin, and LC3
