stem cells and embryology

Question 1

what is the difference between apoptosis and nerosis?

Answer 1

apoptosis is programmed cell death whereas necrosis if less controlled and leads to a release in cytoplasmic content

Question 2

what happens to a cell in apoptosis?

Answer 2

the cell wwould shrink and consense
the cytoskeleton would collapse
the nuclear envelope would dissassamble
DNA ladders would form, the nuclear DNA breaks up into fragments)
phagocytosis occurs (the cell surface is alterned which attracts macrophages)
this rapid removal of the dying cell avoids the damaging consequences of cell necrosis
the organic components of the apoptic cell are recycled by the macrophage

Question 3

what is the purpose of massive cell death?

Answer 3

apoptisis in the developing mouse separates the mouse paw digits to sculpt them
individual fingers and toes are separated by apoptosis
it helps to get rid of the tail of a tadpole
unneeded cells die by apoptosis

Question 4

What does apoptosis depend on?

Answer 4

it depends on an intracellular proteolytic cascade which is mediated by caspases

Question 5

what is apoptosis carried out by?

Answer 5

casapases- these are a family of proteases (these cleave other proteins)
procaspase is activated by cleavage, which amplifies proteolytic cascade
lamin districts the nucleus
PARP
p21WAF1/cip1
cytoskeleton proteins

Question 6

what is CAD and what is it encoded by?

Answer 6

its a caspase-activated DNase
a protein in hymans is encoded for by the DFFB gene
it breaks up the DNA during apoptosis and promotes cell differentiation
it normally an inactive monomer which is inhibited by iCAD

Question 7

what are the 2 different casapse cascades which form the 2 main forms of apoptosis?

Answer 7

extrinsic caspase 8 cascade
intrinsic caspase 9 mitochondrial pathways
both these pathways function to activate the executioner caspases (3, 6, and 7)

Question 8

what happens in the extrinsic pathway of apoptosis?

Answer 8

Fas death receptor binds with the fas ligand on the killer lymphocyte
then fas/fasL complex causes aggregation and cleavage of procaspase-8 or -10 which causes a caspase cascade

Question 9

what happens in the intrinsic pathway of apoptosis?

Answer 9

cytochrome C and Apaf-1 bind to cause aggregation of Apaf-1 and binding of procaspase-9,
this then causes the activation of procaspase 9 which triggers a caspase cascade

Question 10

what proteins regulate the intrinsic pathway of apoptosis?

Answer 10

bak and bax

Question 11

what do bak and bax do?

Answer 11

they: promote death
activate cytochrome C from the mitochondria into the cytosol
form channels in the outer mitochondrial membrane
allow cytochrome c to be released into the cytosol
promote the assembly of apaf-1 to form an apoptosome
procasapse becomes activates within the apoptosome
it triggers a caspase cascade that leads to apoptosis

Question 12

what do survival facotrs do?

Answer 12

they bind to cell surface recpetors
activate intracellular signalling pathways
keep death programme suppressed
regulate members of Bcl-2 family proteins
increase the production of apoptosis-supressing members of the Bcl-2 family

Question 13

what are the 3 ways that extracellular survival factors can inhibit apoptosis?

Answer 13

• they increase the production of anti-apoptotic Bcl2 protein
• they inactivate pro-apoptic BH3-only Bcl2 proteins
• they inactivate Hid, an anti-IPA (inhibitor of apoptosis)