Cell Death Flashcards
Briefly explain Necrosis
Occurs when cells are damaged by injury - exposure to toxic chemicals, mechanical trauma
1)Cell swells
2)Cell contents leak out
3) Inflammation of surrounding tissue
What is apoptosis
Programmed cell death
Name the 2 types of cell death
Necrosis & apoptosis
Why do cells under go apoptosis?
1)Proper growth & development
2)Destroy cells that represent a threat to the organism
Examples of apoptosis leading to proper development
Reabsorption of tadpole tail during metamorphosis to frog
Formation of fingers & toes in foetus requires removal of tissue in between them
What cells may cause a threat to the body & trigger apoptosis
> Cells infected with virus
Cells of the immune system
Cells with DNA damage
Cancer cells
State some morphological changes in apoptosis?
> Chromosomal DNA is usually fragmented
Chromatin condenses & nucleus breaks up
Cell shrinks & breaks down into membrane-enclosed fragments called apoptotic bodies
Apoptotic bodies & fragments phagocytosed by macrophages & nearby cells to remove them from the tissue
What is blebbing?
Cell’s cytoskeleton breaks down & causes membrane to bulge outwards - causes cells to break into apoptotic bodies
What stimuli trigger apoptosis?
> Ligation of cell surface receptors
DNA damage - defects in DNA repair mechanisms
Treatment with cytotoxic drugs or irradiation
Lack of survival signals
Contradictory cell cycle signals
Developmental death signals
What are the initiators & execution of apoptosis?
Caspases (protease enzymes)
What does caspase stand for?
Cysteine-dependent aspartate specific protease
What can insufficient apoptosis lead to?
> Cancer (cell accumulation, resistance to therapy, defective tumour surveillance by the immune system)
Autoimmunity (failure to eliminate autoreactive lymphocytes)
Persistent infections (failure to eradicate infected cells)
What does excessive apoptosis lead to?
> Neurodegeneration (Alzheimer’s, Parkinson’s, Huntington’s)
Autoimmunity (uncontrolled apoptosis induction in specific organs)
AIDS (Depletion of T lymphocytes(
Ischaemia (stroke, myocardial infarction)
How does a caspase work in terms of amino acids?
Binds to cysteine at active site and cleaves target proteins at specific aspartate acids
Where are and what are caspases synthesised from/as?
Synthesised in cells as procaspases
