1030- Apoptosis, necrosis and excitotoxicity

Question 1

Definitions of Apoptosis, necrosis and

excitotoxicity

Answer 1

Activation of a death programme to cause a cell death, traumatic cell death from a acute injury , in neural tissue only

Question 2

Why is preventing release of intracellular molecules particularly
important in the nervous system?

Answer 2

release of excitotoxic
mediators (e.g. glutamate) from dying cells can cause injury to
adjacent neurons

Question 3

Why do cells commit apoptosis?

Answer 3

during metamorphism, to eliminate cells which have served their purpose during development , cells which have been infected by viruses , cancer cells , cells bearing excessive DNA damage , to promote self tolerance

Question 4

phosphatidylserine

Answer 4

usually located on the leaflet of the plasma membrane inside the cells, however inside apoptotic cells it is found on the extracellular membrane and can be detected by annexin

Question 5

What do phagocytes do when they find phosphatidylserine

Answer 5

engulf the dying cell and release inflammatory cytokines

Question 6

What happens to the electrochemical potential of apoptotic cells?

Answer 6

they loose the electrochemical potential which exists across the inner mitochondrial membrane. These changes can then be measured using positively charged fluorescent dyes.

Question 7

What are the causes, characteristics and effects of necrosis?

Answer 7

causes: injury ; ischaemia and hypoxia
Characteristics: damage to the cell membrane and flocculation of chromatin.
Effects : elicts inflammatory response, cell leakage and energy levels are rapidly depleted .

Question 8

What are the causes, characteristics and effects of apoptosis?

Answer 8

causes: chemotherapy , withdrawal of growth factors, contact with cytotoxic t-cells and following a developmental programme. Characteristics; blebbing the cell membrane and chromatin condensation .
Effects - energy levels stay the same, no inflammatory response or cell leakage.

Question 9

What are caspases?

Answer 9

The enzymes which drive apoptosis in multicellular organisms.

Question 10

Explain the apoptotic extrinsic pathway

Answer 10

The use of transmembrane death receptors. These receptors bind to extrinsic ligands and transduce signals which activate capsases.

Question 11

Explain the apoptotic intrinsic pathway

Answer 11

Apoptic stimuli cause mitochondrial membranes to become leaky , this leads to the release of cytochrome c into the cyptoplasm which then activates caspase

Question 12

What does elevated levels of glutamate lead to ?

Answer 12

increased levels of Ca 2+