Lecture 24

Question 1

What are some differences between apoptosis and necrosis (oncotic)?

Answer 1

1. Apoptosis normally only affects singe cells, whereas necrosis often affects a ground/field of cells
2. In apoptosis the cell shrinks in necrosis the cell swells
3. In apoptosis the chromatin condenses and the nucleus fragments, in necrosis nuclear lysis (karyorlysis and karyorrhexis)
4. In apoptosis the cell membrane remains intact, whereas in necrosis, the cell membrane is often damaged
5. In apoptosis the cytoplasm is packed into apoptotic bodies whereas in necrosis the cytoplasm is released
6. In apoptosis there is no inflammation, wheres in necrosis often induces inflammation
7. Apoptosis can be physiological whereas necrosis is always pathological

Question 2

Describe the difference in necrosis versus apoptosis on electron microscopy:

Answer 2

Necrosis - cell appears to have exploded

Apoptosis - cell contents condensed but cell is still intact

Question 3

Describe the process of TNF (macrophage) receptor mediated apoptosis:

Answer 3

1. Macrophage will recognise an old cell, pathogenic cell or cell that has completed its task and then release tumour necrosis factor alpha (TNF) then binds to a death receptor on the surface of the cell example being TNF-R1
2. As a result the death domain (inside of the cell is able to change its shape and bind to two proteins (these include FADD and TRADD)
3. The FADD and TRADD combine together to form the DISC (the death inducing signalling complex)
4. DISC then cleaves procaspase – 8 into caspase 8
5. Then caspase-3 will go on to activate other caspases
6. Caspases are committed and then go on to kill the cell

Question 4

Describe how receptor mediated apoptosis is different if it is activated by a cytotoxic T-cell:

Answer 4

1. T-cell expresses protein on cell called Fas-L then binds to FAS receptor on the cell that is going to die
2. The rest of the process occurs fairly similarly

Question 5

Describe how non-receptor mediated apoptosis occurs:

Answer 5

1. The response is induced by stress/radiation/chemicals
2. Leads to a p53 response then activates BAX/BAK
3. Leakage out of cytochrome c- APAF-1
4. Casp-9 then activates Casp-3

non-caspase dependant necrosis can also occur

Question 6

What is necroptosis?

Answer 6

programmed for of necrosis or inflammatory cell death

Question 7

What is autophagy and what is the cause of it?

Answer 7

• Bodies way of cleaning out damaged cells to regenerate newer and healthier cells
• Wide range of pathological and physiological functions that are associated with it including: cell death, cancer, innate immune system, cardiomyopathy, aging, infectious diseases, fatty liver, Type 2 diabetes, neurodegenerative diseases