apoptosis and necrosis

Question 1

define apoptosis

Answer 1

programmed cell death of a single cell through intracellular sequence of events

Removal of a targeted cell without the release of products harmful to the surrounding cells

Question 2

list 3 inhibitors of apoptosis

Answer 2

Growth factors
Extracellular cell matrix
Sex steroids

Question 3

list 4 inducers of apoptosis

Answer 3

Glucocorticoids
Free radicals
Ionising radiation
DNA damage

Question 4

what are the 3 types of DNA damage that can cause apoptosis?

Answer 4

Single-strand break
Base alteration
Cross-linkage

Question 5

name a disease caused by a LACK of apoptosis

Answer 5

cancer:

lack of apoptosis – mutated p53 gene producing faulty p53 protein so it cannot control apoptosis

Question 6

name a disease caused by TOO MUCH apoptosis

Answer 6

HIV:

too much apoptosis – kills the antibodies in the blood so the body can’t defend itself.

Question 7

define necrosis

Answer 7

traumatic death

death of most or all of the cells in an organ or tissue due to disease, injury, or failure of the blood supply.

There is bioenergetic failure and loss of plasma membrane integrity

Question 8

give 5 clinical examples of necrosis

Answer 8

Toxic spider venom
Frostbite
Cerebral infarction
Avascular necrosis of bone – femur has single arterial supply through the neck of the femoral head
Pancreatitis

Question 9

what are the 4 types of necrosis

Answer 9

1. coagulative
2. Liquefactive
3. Caseous

4.Gangrene

Question 10

what is coagulative necrosis? (where does it happen, what is its cause)

Answer 10

Most common type
Can occur in most organs
Cause by ischaemia

Question 11

what is liquefactive necrosis? (where does it happen, what is its cause)

Answer 11

Occurs in the brain due to its lack of substantial supporting stroma

Question 12

what is Caseous necrosis? (what is its distance pattern, which disease is characterised by this form)

Answer 12

Causes a ‘cheese’ pattern
TB is characterised by this form of necrosis

Question 13

what is gangrene? what does it look like?

Answer 13

Necrosis with rotting of the tissue
Affected tissue appears black due to deposition of iron sulphide (from degraded haemoglobin)

Question 14

what are the different mechanisms of apoptosis?

Answer 14

intrinsic - apoptosis in response to internal stimuli eg. DNA damage

extrinsic - apoptosis in response to external stimuli

Question 15

what are the 2 groups of modulators involved in intrinsic apoptosis?

Answer 15

Bcl-2 family

Bax family

Bcl-2:Bax ratio determines the cell’s susceptibility to apoptotic stimuli

Question 16

how is the extrinsic pathway of apoptosis carried out?

Answer 16

specific ligands binding at ‘death receptors’ on the cell surface, initiate signal transduction cascade

Question 17

what is the execution phase is apoptosis?

Answer 17

common to both pathways (intrinsic and extrinsic)

Both pathways results in a cascade activation of caspases

initiator caspases -> executioner caspases -> degrade the cells

Question 18

what happens to a cell structure when it undergoes apoptosis?

Answer 18

Nuclear shrinkage (pyknosis)
DNA Fragmentation (karyorrhexis)
Cell shrinks

However - Retains an intact plasma membrane

dead cells are then phagocytosed

Question 19

main differences between apoptosis and necrosis:

• stimuli

Answer 19

apoptosis: physiological, intracellular stimulus

necrosis: pathophysiological, extracellular stimulus (injury, disease)

ie, apoptosis happens in the healthy body all the time, whereas necrosis is often due to a disease

Question 20

main differences between apoptosis and necrosis:

• inflammation and tissue damage

Answer 20

apoptosis: no inflammation, no secondary tissue damage, integrity of cellular structures maintained

necrosis: inflammation and secondary tissue damage, swelling and disintegration of cellular structures

Question 21

main differences between apoptosis and necrosis:

• ATP dependent?

Answer 21

apoptosis - to activate cell death pathway need ATP

necrosis - abnormal pathway, no ATP needed

Question 22

give an example of necrosis

Answer 22

renal infarction

Question 23

What is the role of p53 protein?

Answer 23

p53 protein looks for DNA damage, if damage is present p53 switches on apoptosis.

Question 24

Activation of which family of protease enzymes can turn on apoptosis?

Answer 24

Caspases.

Question 25

Activation of what receptor can activate caspase and therefore apoptosis?

Answer 25

FAS receptor