Control of Programmed Cell Death (Apoptosis)

Question 1

Apoptosis

Answer 1

Apoptosis is triggered by cell death signals that can be internal or external

Apoptosis is essential during development of an organism to remove cells no longer required as development progresses or during metamorphosis.

Cells may initiate apoptosis in the absence of growth factors.

External signal - The production of death signal molecules from lymphocytes is an example of an external death signal

Internal signal - DNA damage is an example of an internal death signal

Question 2

External and internal death signals

Answer 2

External death signal - External death signal molecules
bind to a surface receptor protein and trigger a protein cascade within the cytoplasm

Internal death signals - An internal death signal resulting from DNA damage causes activation of p53 tumour-suppressor protein.

Both types of death signal result in the activation of caspases (types of protease enzyme) that causes the destruction of the cell)