Hudmon Lec 2

Question 1

what is apoptosis

Answer 1

phagocytosis of apoptotic cells and fragments

Question 2

what is necrosis

Answer 2

enzymatic digestion and leakage of cellular contents

Question 3

what are the physiological causes of the apoptotic pathways

Answer 3

1. Programmed destruction of cells during embryogenesis: many
2. Involution of hormone-dependent tissues upon hormone deprivation: endometrial cell breakdown during menstrual cycle
3. Cell loss in proliferating cell populations: intestinal crypt epithelia
4. Elimination of potentially harmful self-reactive lymphocytes: before or after maturation
5. Cell death induced by cytotoxic T lymphocytes

Question 4

what are the pathological causes of the apoptotic pathways

Answer 4

DNA damage; accumulation of misfolded proteins; cell injury in certain infection (viral infections); pathological atrophy in parenchymal organs after duct obstruction (pancreas, kidney, and parotid gland)

Question 5

what is the intrinsic pathway

Answer 5

1. Mitochondrial (intrinsic) pathway
   - Cell injury
   GF withdrawal
   –> DNA damage (radiation, toxins, free radicals)
   –> Protein misfolding (ER stress)

Question 6

what is the extrinsic pathway

Answer 6

2. Death receptor (extrinsic) pathway
   - Receptor-ligand interactions
   –> Fas
   –> TNF receptor

Question 7

what are the two apoptotic pathways

Answer 7

intrinsic and extrinsic

Question 8

what is the role of BCL-2 in apoptosis

Answer 8

• Bax, Bak, and Bad proteins can increase mitochondrial membrane permeability by forming a dimer and inserting into the mitochondrial membrane. So this is called pro-apoptotic proteins
• Bcl-2 and Bcl-x can bind Bax family proteins and inhibit their function so this is called anti- apoptotic proteins
  1. central players

Question 9

what is the role of Cytochrome C in apoptosis

Answer 9

• Caspases (cysteine-aspartic proteases, cysteine aspartases or cysteine-dependent aspartate-directed proteases)
• released from mitochondria can activate caspase-9 to initiate caspase cascade

Question 10

what is the role of the 2 types of caspases in apoptosis

Answer 10

Initiators and executioner (caspase-3 and 7)

Question 11

what is the role of activated caspases

Answer 11

1. activate other proteases
   –> Degradation of cytoskeletal proteins
2. can activate endonucleases
   –> Cleavage of DNA leading to DNA fragmentation (DNA ladder)

Question 12

what is the role of blebs formation

Answer 12

Dying cells collapse into cytoplasmic buds and apoptotic bodies

Question 13

what is the role of phagocytosis in apoptosis

Answer 13

• bodies of macrophages
• Dead cells are cleared before they can release their cytoplasmic contents
• Prevents triggering an inflammatory response
• Nothing remains of dead cell

Question 14

what mechanisms of cell injury are there

Answer 14

1. ATP depletion
2. mitochondria damage
3. membrane damage
4. increased ROS
5. calcium influx

Question 15

what is the cell size of necrosis vs. apoptosis

Answer 15

necrosis: enlarged
Apoptosis: reduced

Question 16

what is the nucleus of necrosis and apoptosis

Answer 16

necrosis: Pyknosis → karyolysis
Apoptosis: Fragmentation into nucleosome sized fragments

Question 17

what is the plasma membrane for necrosis and apoptosis

Answer 17

necrosis: disrupted
apoptosis: Intact, but altered structure

Question 18

what is the cellular contents of necrosis and apoptosis

Answer 18

necrosis: enzymatic digestion, leakage
apoptosis: Intact, in apoptotic bodies

Question 19

what is the inflammation in necrosis and apoptosis

Answer 19

necrosis: frequent
apoptosis: none

Question 20

does necrosis or apoptosis deal with physiologic or pathologic roles

Answer 20

necrosis: Invariably pathologic
apoptosis: Often physiologic; may be pathologic