Question

please help me answer the following questions

Apoptosis:

What are triggers? What does this cause in cell? What is importance of location of PS
​(phosphatidyl serine) in cell membrane?

Caspases (role and examples of targets in cell)

Apoptosome (look at role of cytochrome c)

Answer 1

What are triggers? What does this cause in cell?

Triggers can be intracellular or extracellular death signals which causes apoptosis. Apoptosis, also called programmed cell death is a normal phenomenon which occurs often in multicellular organisms. It’s a process which is activated within the cell and it leads to the death of the said cell without damaging it’s neighboring cells. All nucleated animal cells contain various inactive procaspases, which when activated into caspase on receiving death signals, triggers the death of the cell by cleaving specific proteins in the cytoplasm and nucleus. These death signals can be intracellular or extracellular in nature. They can vary from DNA damage and viral infection to developmental cues such as those leading to the degradation of a tadpole's tail. Damaged or stressed cells can trigger the procaspase activation from within the cell(intracellular death signals). The activation of death receptors on the cell surface can also lead to procaspase activation from outside the cell (extracellular death signals).

What is importance of location of PS  (phosphatidyl serine) in cell membrane?

Phosphatidylserine is a phospholipid which is a part of the cell membrane. It is mainly located in the inner leaflet of the plasma membrane. When a cell undergoes apoptosis, it is seen in the extracellular (outer) surface of the cell and this acts as a signal for macrophages to engulf the cells.

Caspases (role and examples of targets in cell) :

Caspases mediates apoptosis in multicellular organisms. It triggers the death of the cell by cleaving specific proteins in the cytoplasm and nucleus.Examples of targets of caspases are: structural proteins like actin, components of cellular DNA repair mechanisms like ADP-ribose.

Apoptosome (look at role of cytochrome c) :

During apoptosis, cytochrome c are released from the mitochondria in response to internal or external death signals. This cytochrome c binds to the the cytosolic protein Apaf-1 and leads to the formation of apoptosome, a quaternary protein stucture.