Cell Aging and Death ✓ Flashcards
Necrosis
death of tissues
no energy required
always pathological
Coagulative necrosis
preservation of cell outline
microenvironment too toxic for proteolysis (cells cannot clean up mess)
common, often seen in MI
Liquefactive necrosis
no cell structure remains
viscous mass of dead cells left behind (pus)
bacterial + fungal infections, brain injury
Caseous necrosis
‘cheesy’
TB
Apoptosis
programmed cell death in response to specific signals
requires energy
can be physiological or pathological
example of physiological apoptosis
normal growth
removal of self-reactive lymphocytes
hormonal-dependant involution
examples of pathological apoptosis
injury, chemo, viral infection
two types of pathway for apoptosis
extrinsic or intrinsic
extrinsic apoptosis
initiated death receptors which activate caspases
two death receptor in extrinsic apoptosis
Fas and TNF
Fas
recognition of the self
apoptosis in lymphocytes
fas mutations = autoimmune diseases
TNF
apoptosis in association with inflammation
Intrinsic apoptosis
mitochondrial pathway
growth signals promote anti-apoptotic molecules in the mitochondrial membrane, when these are removed, they’re replaced by Bax and Bak which stimulate caspase release
p53
sense damage to DNA, can halt cell cycle
if DNA cannot be repaired, stimulates caspases
Cellular aging
can be caused by
- oxidative stress (free radical damage)
-accumulation of metabolic by-products (lipofuscin)
calorie restriction can extend life - reduces IGF signalling which can silence specific genes
