Under certain conditions, cytochrome c can trigger apoptosis, or programmed cell death, by activating cytosolic proteins known as caspases.

(a) Why doesn’t cytochrome c trigger apoptosis in healthy cells?
(b) What must happen in order for cytochrome c to activate the caspases

A) Cytochrome C reduction in healthy cells B) Cytochrome cause the oligomerization of APAF1 that cause the activation of Caspase-9, which activates the Caspase-3 and Caspase-7 that ultimately lead to apoptosis.

Explanation:

Apoptosis is the programmed cell death which is performed to get rid of unnecessary and damaged cells through biochemical changes in higher animals. In apoptosis the cell shrinks, cytoskeleton collapse, nuclear membrane disassemble and DNA break into fragments.

a) Cytochrome C is present in intermembranel spaces of mitochondaria and the heme group of cytochrome C accepts electrons from Complex bc1 and transferr to complex IV. Thus as the healthy cells requires proper energy to perform its regular functions the cytochrome keep reducing rapidly in it and this inhibit the cytochrome to initiate the apoptosis in healthy cell.

B) Cytochrome C is released from mitochondria in apoptotic cell and it cause the oligomerization of the inactive Apoptosis protease activating factor-1. It form apoptosome complex with APAF1 that initiate and activate the caspases. These caspases are then involved in degradation of protein.

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