Molecular Cell Biology

Question 1

Which cyclin/CDK is the link between the cell cycle and the external environment?

Answer 1

Cyclin D/CDK 4

Question 2

What does INK4 the CDK inhibitor protein inhibit? And what is the consequence?

Answer 2

It binds CDK4 therefore cyclin D can’t bind and hence Rb isn’t phosphorylated and therefore cannot bind E2F therefore transcription cannot occur.

Question 3

Which inhibitor protein binds the cyclin (E/A) - CDK 2 complexes?

Answer 3

KIP

Question 4

What type of inhibitor is INK4?

Answer 4

binary

Question 5

What type of inhibitor is KIP?

Answer 5

ternary

Question 6

What does KIP prevent?

Answer 6

Activation of cyclin (E/A)-CDK2 complex

Question 7

True of false - some cells spend entire life in G0 phase and some divide infrequently.

Answer 7

True - hepatocytes = infrequently, neutrons = lifetime

Question 8

Do cancer cells have Restriction point?

Answer 8

No

Question 9

Do cancer cells respond to contact inhibition?

Answer 9

No

Question 10

What is an example of a positive GF?

Answer 10

E2F

Question 11

What is an example of negative GF?

Answer 11

TGF-beta

Question 12

Do cancer cells have limited replicative life span?

Answer 12

No - they can remake telomeres when eroded.

Question 13

What is apoptosis?

Answer 13

Programmed call death

Question 14

What can the malfunction of apoptosis lead to?

Answer 14

Cancer (TNF produced by macrophages activates extrinsic pathway), neurodegeneration, AIDS (HIV deactivates Bcl-2), ischemic stroke, autoimmune (LUPUS)

Question 15

What happens if there is too much apoptosis?

Answer 15

Loss of SC, problems with regeneration.

Question 16

What happens there is too little apoptosis?

Answer 16

Too many SC, problems with regeneration and function - leukaemia.

Question 17

What is necrosis?

Answer 17

Lethal cell injury and accidental cell death in living organisms.

Question 18

What are the characteristics of apoptosis?

Answer 18

No loss of membrane integrity, shrinking of cytoplasm and nuclear condensation, mito release death signals, aggregation of chromatin at nuclear membrane.

Question 19

What are the characteristics of necrosis?

Answer 19

Loss of membrane integrity, swelling of cytoplasm and mito, total cell lysis, disintegration of organelles, no vesicle formation.

Question 20

What is the important of apoptosis in adults?

Answer 20

Tissue remodelling/maintenance, loss of endometrium at start of menstruation, maintenance of organ size and function by balancing proliferation.

Question 21

What is the importance of apoptosis in development and morphogenesis?

Answer 21

Eliminates excess cells, eliminates non-functional cells.

Question 22

What is the importance of apoptosis in disease?

Answer 22

Viral infection - CTLs kill infected cells.
Immune system - after prolonged immune response body removes effector cells.
DNA damage - damage to genome –> cancer
Cancer therapy induces apoptosis.

Question 23

What are the +ve signals that make a cell commit suicide?

Answer 23

continuous stimulation from other cells, and adhesion

Question 24

What are the -ve signals that make a cell commit suicide?

Answer 24

more free radicals and oxidants, DNA related inducers e.g. UV light, physiological activators e.g. removal of GF.

Question 25

What are the 4 stages of apoptosis?

Answer 25

Death signal, execution, engulfment, degradation.

Question 26

Give three assays that detect apoptotic cells.

Answer 26

DNA fragmentation (electrophoresis) morphological changes (blabbing, fragmentation, skrinkage) losso f membrane integrity (loss of dye exclusion)

Question 27

Describe the intrinsic pathway of apoptosis

Answer 27

DNA damage and p53, mito/cyt C, initiator caspase 9, effector caspase 3, apoptosis.

Question 28

Describe the extrinsic pathway of apoptosis.

Answer 28

Death ligand, death receptors, initiator caspase 8, effector caspase 3, apoptosis.