can someone please explain to me, the malfunctions in apoptosis that result in deviant cell behaviour leading to disease including cancer and also the intrinsic and extrinsic pathway?
Thank you
I'm just going to copy it from my notes given I don't know how much you already know about them. Let me know if you have questions about any of this.
Malfunctions in apoptosisCancer is caused by a damaged cell not undergoing apoptosis. These cells divide rapidly, creating large lumps called tumours. There are many reasons why apoptosis fails to occur.
Overactive apoptosis: Leads to diseases such as Huntington’s, Alzheimer’s, type 1 diabetes
Underactive apoptosis: Leads to diseases such as cancer.
ApoptosisTriggers:
-Cellular injury
-DNA damage
-Viral infection
-Old age
-Cell no longer needed
Mitochondrial (intrinsic) pathway:
A signal causes the mitochondria to release cytochrome C (a protein usually involved in the electron transport chain). Cytochrome C activates caspases in the cell.
When mitochondria are damaged they release signals called cytochromes. They act as signalling molecules for intracellular receptors that initiate apoptosis.
Death receptor (extrinsic) pathway:
Initiated by a signalling molecule binding to a death receptor, which causes the activation of enzymes called caspases.
Apoptosis:
Caspases are activated by either of the apoptotic pathways. Caspases are enzymes that cleave protein molecules, breaking down the cytoskeleton of the cell, as well as other proteins in the cytoplasm and nucleus. The caspases activate other enzymes called DNAses, which cut nuclear DNA. Blebs form on the surface of the cell, and the cell fragments into a group of vesicles. The contents of the cell never enter their environment, and are always contained within a phospholipid bilayer. The vesicles (or ‘blebs’ or ‘apoptotic bodies’) are engulfed by phagocytes (e.g. macrophages), and their contents are recycled.