Biology unit 7 test 5
how to get rid of unwanted cells cleanly
- contract with another death process; necrosis
- occurs in frogs (tadpol has tail cells removed)
How to regulate cell number and cell size
apoptosis - programmed cell death
what is apoptosis
- proteolytic cascade carried out by sparse family of enzymes
- present in all cells as inactive precurors - procascades
- can be rapidly activated in response to apoptotic signals
what is an apoptotic signal
- a signal that is all or none
- irreversible once it reaches a certain point
- regulated by Bcl2 family of proteins push cells to death through apoptotic pathway
when do you want cell death to occur
when there is cell stress, dna damage, free radicals, lack of survival factors
how is apoptosis triggered
1. release of cytochrom C
2. Multiple cytochrome C and Adaptor proteins bind
3. recruitment of procaspase - a molecules
4. apoptosome is formed and actrivation of procaspase - a occurs causing caspade cascade leading to apoptosis
what is 'pruning' in the developing nervouse system
- cell death matched number of nerve sells to number of target cells
- survival factors often act by shifting the balance of pro- and anti-apoptic Bcl-2 family members
- Bcl2 protein block apoptosis
what are mitogens
they push cells past the G1/S restriction point
what are growth factors
- if cell divides without growing, daughter cell will get smaller and smaller
- neurons, muscle cells permanently stop dividing, then start to grow/specialize "terminally differentiated
hyperplasia definition
more cells
hypertrophy definition
bigger cells
Positive regulators in cell growth
- inhibition protein of degradation
- stimulation of protein synthesis
negative regulators of growth
- oppose actions of growth factors
- limits muscle grows by inhibiting differentiation of precursors into muscle fibres during fetal development
- inhibits an RTK-induced pathway that drives protein synthesis and cause hypertrophy in muscle
what is myostatin
- a negative growth factor expressed in skeletal muscle