cell death

Question 1

necrosis =

Answer 1

uncontrolled large scale cell death

Question 2

apoptosis =

Answer 2

programmed cell death (self suicide of 50 billion cells per day)

Question 3

what are the physical causes of necrosis?

Answer 3

trauma, cuts, burns, extreme temps (e.g. frostbite → cellular fluid freezes)

Question 4

what type of toxins cause necrosis?

Answer 4

internal = bacterial toxins, external = snake venom

Question 5

how does acute hypoxia/ischaemia cause necrosis?

Answer 5

stroke → tissues die from deprived blood flow → no O2

Question 6

describe the process of reversible necrosis

Answer 6

ATP dependent pumps stop working due to lack of O2 → so ion conc increases → water moves into cell by osmosis

membrane integrity compromised from cell and organelle swelling

Question 7

describe irreversible necrosis

Answer 7

cellular calcium level too high → autolysis occurs (destruction of cells by own enzymes especially is lysosome bursts) → cell lysis (breaking membrane down) → inflammatory response activated

Question 8

describe the process of apoptosis

Answer 8

cell shrinkage → DNA fragmentation and nuclear breakdown → breakdown of cytoskeleton → formation of apoptotic bodies → phagocytosis of apoptotic bodies

(no inflammatory response)

Question 9

why can’t apoptosis occur in ischaemic conditions?

Answer 9

requires O2

Question 10

what is apoptosis’ relationship with autophagy?

Answer 10

if lots of organelle death occurs in 1 cell it will be phagocytosed

Question 11

describe the physiological situations where apoptosis occurs

Answer 11

→ tissue size maintenance
→ developmental cell loss
→ removal of immune cells after immune response
→ hormone → menstruation

Question 12

describe the pathological situations where apoptosis occurs

Answer 12

→ DNA damage (by radiation, oxidation, stress) in own cell nucleus
→ induced in virally infected cells to prevent spread of virus

Question 13

give 4 examples of developmental apoptosis

Answer 13

C.elegans nematode worm:
→ 1mm long with 1100 cells → 131 die during development

metamorphic in tadpoles:
→ surge in thyroid hormone → initiates apoptosis in tail cells → results in adult frog

digit formation in mice:
→ web cells are apoptosis by releaser of local signalling proteins

refinement of neural connections:
→ apoptosis adjusts no. of neuronal cells to size of target by competition for survival factors

Question 14

give an event where both necrosis and apoptosis are involved

Answer 14

brain ischaemia:
→ cells in middle → site of O2 starvation → die through necrosis

→ cells around edge → die through apoptosis → prevents the spread of cell death

Question 15

model for studying apoptotic pathways =

Answer 15

C.elegans

Question 16

Ced genes are involved in ________________ leading to engulfment of _______ via ________

Answer 16

recognition of apoptotic signals, apoptotic cells, phagocytosis

Question 17

describe the basic pathway of Ced genes

Answer 17

IL-1 → CED-9 → CED-4 → CED-3 → apoptosis

Question 18

which CED genes are pro-apoptotic?

Answer 18

IL-1, CED-4, CED-3

Question 19

which CED gene is anti-apoptotic?

Answer 19

CED-9

Question 20

______ are executioners of cell death and essential for apoptosis

Answer 20

caspases

Question 21

EGL-1 =
CED-9 =
CED-4 =
CED-3 =

Answer 21

BH3
BCL2
APAF1
caspases

Question 22

what are the 2 pathways for the activation of apoptosis?

Answer 22

intrinsic and extrinsic

Question 23

describe the extrinsic pathway for activation of apoptosis

Answer 23

→ tumour necrosis factor family (TNF)
→ 6 related death receptors in trimmers on cell surface

apoptotic signal → Fas ligand on killer lymphocyte (CD4+) binds to death receptor → activation of caspase 8 → death inducing signalling cascade activated

Question 24

describe the intrinsic pathway for activation of apoptosis

Answer 24

takes place inside the cell being apoptosed

triggered by DNA damage → release of mitochondrial contents or developmental signals

Question 25

what decides if cytochrome C or other mitochondrial proteins are released?

Answer 25

balance between pro and anti apoptotic factors → BLC-2 family proteins

EGL-1 (homolog BH3) → only protein → pro apoptotic,
CED-9 (homolog Bcl2) = anti apoptotic

apoptotic stimulus causes Bcl2 family proteins in mitchochondrial membrane to gather → form channels → allows mitochondrial contents to pass through