29 Flashcards
What is replicative senescence?
Cells cannot divide forever and can only divide a finite number of times
What is telomerase?
An enzyme that maintains the ends of chromosomes
What cells express telomerase?
Germ cells and stem cells
Why do normal cells senesce?
Due to the erosion of telomeres
What happens at G0?
Most cells exit the cell cycle programme as part of a differentiation programme
What is necrosis?
Programmed cell death however the contents leak out as it dies and the body reacts by intiating an immune response which can lead to inflammation
What is apoptosis?
Physiological cell death
Energy dependent
Metabollically active
Endogenous cellular processes
Membrane integrity is maintained and where the dying cells do not elicit an inflammatory reaction
What is DNA laddering?
A process in apoptosis whereby DNA is chopped in into fragments in a specific way
What are the morphological features of apoptosis?
The nucelei show condensation Formation of Apoptotic bodies There is specific DNA fragmentation by enzymes Energy dependent process Regulated by genes
What are caspases?
Special proteases
C for cysteine and Asp for aspartic acid
What are two types of caspases?
Initiator caspase
Executionar caspase
What are the two basic pathways of apoptosis?
Extrinsic pathways and intrinsic pathways
What is the extrinsic pathway of apoptosis?
Activated by cell surface receptors
Death receptors
Activated by ligands binding to the receptors
What is the intrinsic pathway of apoptosis?
Activated by events within cells
Depends on mitochondria
Release of cytochrome c which can work with other proteins to activate
Why is it important to regulate mitochondrial permeability?
Suitable apoptotic stimulus causes increased permeability which promotes apoptosis via an intrinsic way
proteins form channels to release cytochrome c
