apoptosis

Question 1

What are the stages of cell morphology during apoptosis

Answer 1

1. cell loses volume
2. cell membrane becomes ruffed and blebs
3. RER and cell membrane combine and cell
4. Cell and nucleus shrink
5. chromosomes condense
6. nucleus fully condenses
7. nucleus breaks up
8. cell fragments in self-contained apoptotic bodies (no inflammation)

Question 2

What is secondary necrosis

Answer 2

Where small self-contained cell fragments from apoptosis break down

Question 3

What is phosphatidylserine

Answer 3

A type of phospholipid that is present on the inner monolayer in healthy cells.
PS externalisation causes cell to become a target for apoptotic cells to be phagocytosed.

Question 4

How is externalization of phosphoserine controlled

Answer 4

• in stead state flipases actively (requires ATP) maintain PS on the inner monolayer preserving the lipid asymmetry
• PS is externalised by scramblases during apoptosis because the cell is committed to death

Question 5

What are the stages of the intrinsic (mitochondrial pathway) apoptotic pathway

Answer 5

1. signal inside the cell - due to stress e.g. DNA damage
2. pro-apoptotic signals open pours (formed by bax proteins - in non-apoptotic cells BCl-2 proteins inhibit these) on mitochondria
3. mitochondrial proteins (i.e. cytochrome C) are released into the cytosol.
4. cytochrome C binds with apoptosis protease activating factor to form apo apoptosome which which activates caspases for apoptosis

Question 6

What are the stages of the extrinsic apoptosis pathway

Answer 6

1. ligand binds to death receptors
2. activation leads to caspase cascade

Question 7

What are the stages of the caspase cascade

Answer 7

1. procaspase activated by losing the prodomain
2. These activated forms are initiator caspases
3. These activate executioner caspases - these cleave essential proteins causing cell death

Question 8

What are the functions of caspases

Answer 8

• cut off from surrounding cells
• reorganise cytoskeleton
• shut down DNA replication and repair
• interrupt DNA splicing
• destroy DNA
• disrupt nuclear structure
• disintegrate cells in apoptotic bodies

Question 9

What is necrosis

Answer 9

accidental cell death - it isn’t contained contained and triggers an immune response.
- there is irreversible swelling, membrane disintegration and cell lysis

Question 10

What are the key features of necrosis

Answer 10

• cell adhesions are still intact
• changes in mitochondrial morphology
• cell and organelles shrink
• changes in mitochondrial morphology
• ER dilates
• nuclear chromatin flocculates
• membrane breaks down and lysosomal enzymes are released
• damaging to surrounding tissue

Question 11

What are the key features of apoptosis

Answer 11

• loss of cell-cell contacts
• loss of microvilli
• cytoplasm condensed and cell shrinkage
• ER dilate (bubbled appearance)
• plasma membrane becomes convoluted
• cell breaks down and apoptotic bodies form
• non-inflammatory

Question 12

What is cytochrome C

Answer 12

• usually found in the inner mitochondrial membrane, involved in electron transport in phosphorylation
• during apoptosis - released through pores in mitochondria and activate apoptosomes

Question 13

What is the annexin V binding assay (flow cytometry)

Answer 13

Annexin V-PE binds to the membrane when PS is externalised and so can be used to monitor apoptosis when fluorescently labelled

Question 14

What are the apoptotic hallmarks of cancer

Answer 14

• defects in normal programmed cell death mechanisms
• subverting the need for exogenous survival factors
• allowing time for accumulative genetic alterations
• promote resistance to the immune system
• cancer associated defects in apoptosis

Question 15

How do defects in normal programmed cell death mechanisms act as a hallmark of cancer

Answer 15

Plays a major role in parthenogenesis of tumours, allowing neoplastic cells to survive beyond their intended lifespans

Question 16

How does allowing time for accumulative gene alterations act as a hallmark of cancer

Answer 16

deregulated cell proliferation, interferes with differentiation, promotes angiogenesis and increases cell motility and invasiveness during the tumour progression.

Question 16

How do subverting the need for exogenous survival factors act as a hallmark of cancer

Answer 16

provides protection from hypoxia and oxidative stress as the tumour mass expands

Question 17

How does promoting resistance to the immune system act as a hallmark of cancer

Answer 17

Many of the weapons cytolytic T cells and natural killer cells use for attacking tumours depend on integrity if the apoptosis machinery.

Question 18

How do cancer associated defects in apoptosis act as hallmarks for cancer

Answer 18

Plays a role in chemoresistance and radio resistance, increasing the threshold for cell death and thereby requiring higher doses for tumour killing.