Cell death

Question 1

What are the three phases of apoptosis?

Answer 1

Commitment
Execution
Clearance

Question 2

What happens during the commitment phase of apoptosis?

Answer 2

The cell receives signals which induce apoptosis (can be from external source or internal)

Question 3

What happens during the execution phase of apoptosis?

Answer 3

Morphological and biochemical changes occur

Question 4

What happens during the clearance phase of apoptosis?

Answer 4

Apoptotic bodies are phagocytosed

Question 5

What can happen to induce apoptosis?

Answer 5

Cell injury
Loss of survival factors
Death receptor received

Question 6

Give an example of a death receptor

Answer 6

FasL ligand brought to Fas receptor on cell by cytotoxic T cell - induces cell signalling cascade which results in apoptosis, and T cell dies

Question 7

Give an example of loss of survival factors

Answer 7

RPE stops the secretion of PEDF and VEDF growth factors which usually suppress apoptosis

Question 8

What could cause cell injury?

Answer 8

Microbial agents
Physical agents
Chemical agents
Immune injury
Lack of nutrients
Metabolic changes

Question 9

Give an example of a cell injury, and the response to it

Answer 9

Radiation damage causes extensive DNA damage
p53 transcription factor activated which causes gene expression
DNA is repaired, or apoptosis occurs if irrepairable

Question 10

What happens within the nucleus during apoptosis?

Answer 10

Chromatin condenses
Nucleus condenses and fragments

Question 11

What happens outside of the nucleus during apoptosis?

Answer 11

Cytoplasm constricts, causing cell to shrink and increase in density
Cell membrane buds/blebs

Question 12

What is the final stage of apoptosis?

Answer 12

Formation of apoptotic bodies and their phagocytosis

Question 13

How does necrosis happen?

Answer 13

Cells swells, organelles disfunctional
Blebs (leaks) into external environment (cellular materials exposed)
Inflammatory reaction occurs

Question 14

Give an example of necrotic disease

Answer 14

Gas gangrene (caused by low oxygen levels)

Question 15

What happens in a cell once it receives a death receptor?

Answer 15

Caspase cascade is activated

Question 16

Which caspases initiate the cascade?

Answer 16

1
2
8
9
10

Question 17

Which caspases are effectors?

Answer 17

3
6
7

Question 18

What are caspases and what do they do?

Answer 18

Enzymes which cleave each other in a cascade fashion and activate other enzymes which induce DNA breakage and cell disassembly

Question 19

How is apoptosis regulated?

Answer 19

Factors which inhibit or encourage apoptosis

Question 20

Give an example of a pro-apoptotic factor

Answer 20

Bax subfamily
BH3 subfamily

Question 21

Give an example of an apoptosis inhibitor

Answer 21

BCL-2 subfamily
Inhibitors of apoptosis proteins
Caspase inhibitors

Question 22

Give an example in the eye where over apoptosis occurs

Answer 22

Glaucoma (RGCs)