AP BIOLOGY

Detailed explanation-1: -Intrinsic pathway of apoptosis The intrinsic apoptosis pathway begins when an injury occurs within the cell. Intrinsic stresses such as oncogenes, direct DNA damage, hypoxia, and survival factor deprivation, can activate the intrinsic apoptotic pathway.

Detailed explanation-2: -The intrinsic apoptosis pathway is initiated by, for example, chemotherapy and/or radiotherapy. It is activated by a range of exogenous and endogenous stimuli, such as DNA damage, ischemia, and oxidative stress. Moreover, it plays an important function in development and in the elimination of damaged cells.

Detailed explanation-3: -Excess cellular levels of ROS cause damage to proteins, nucleic acids, lipids, membranes and organelles, which can lead to activation of cell death processes such as apoptosis. Apoptosis is a highly regulated process that is essential for the development and survival of multicellular organisms.

Detailed explanation-4: -Reactive oxygen species (ROS) are short-lived and highly reactive molecules. Low doses of ROS activate cell survival signalling pathways: UPR, Nrf2. High doses of ROS activate cell death signalling pathways: apoptosis and necroptosis. ROS activate mitochondrial, death receptor and ER pathways of apoptosis.