apoptosis Flashcards
(15 cards)
What is apoptosis?
It is the natural and controlled death of cells within our body.
Cells die by apoptosis – programmed cell death
pathways of apoptosis
intrinsic pathway
extrinsic pathway
intrinsic pathway
- If there is damage inside the cell (eg. mutated DNA),
mitochondria release cytochrome c - Cytochrome c binds with intrinsic proteins to form an
apoptosome which activates caspase enzymes. - Caspases initiate apoptosis.
role of caspase enzymes
. When a cell is no longer needed or is damaged, it should break down safely so it doesn’t harm the body. Caspases act like tiny scissors that cut up parts of the cell to help it die in a clean and controlled way.
4 stages of apoptosis
Activation of caspases
Digestion of cell contents
Cell shrinkage
Blebbing and formation of apoptotic bodies
Activation of caspases
mitochondria release cytochrome C
when internal damage is detected.
Digestion of cell contents :
caspases cleave/cut internal
proteins (cytoskeleton) & breakdown organelles
Cell shrinkage :
the cell and nucleus shrink/collapse
Blebbing and formation of apoptotic bodies :
the membrane
bulges and forms membrane enclosed vesicles called
apoptotic bodies containing broken down cell contents.
when apoptosis is needed for proper development
The resorption of the tadpole tail
The formation of the fingers and toes of the fetus
The sloughing off of the inner lining of the uterus (menstrual cycle)
The formation of the proper connections between neurons in the
brain
apoptosis desroys cells
Cells infected with viruses
Cells of the immune system once they are no longer
needed (after infections)
Cells with DNA damage
Cancer cells
Necrosis
Necrosis is unregulated death of cells.
This can occur when a cell is damaged by :
- infection (by viruses & bacteria)
- injury (physical damage eg. cuts, burns etc.)
The cell swells, bursts its
cell membrane and the contents are released into the surrounding tissues – causing
INFLAMMATION
(not seen with apoptosis)
- too little apoptosis
With less apoptosis and more cell growth, this may lead to
the formation of tumours ( masses of damaged cells)
2 types of tumours
- benign
not cancerous - malignant
- these are cancerous.
( metasis can spread from one part of the body to another)
Excessive apoptosis
When there is too much apoptosis occurring – too many healthy cells are programmed to die. Many diseases that affect the nervous system (neurological
disorders) are linked to increased rates of apoptosis.
eg. Huntington’s disease, Dementia, Parkinson’s disease,
Alzheimer’s disease.
