Final answer:
In apoptosis, the intrinsic pathway is activated by internal factors such as DNA or organelle damage. The protein p53 is crucial as it can halt cell division for repairs or initiate apoptosis if the damage is unfixable.
Step-by-step explanation:
In apoptosis, the intrinsic pathway is triggered by internal problems such as organelle damage or DNA damage. This type of cell death is programmed and is a way for the body to dispose of cells that are no longer needed or are a threat to the organism, such as those with irreparable DNA damage. Proteins such as p53 play a key role in this process; they can arrest the cell cycle to allow for DNA repair. If the damage is too extensive, p53 can also lead to the initiation of apoptosis to prevent the damaged cell from proliferating, which could lead to cancer. Apoptosis is an essential mechanism for maintaining the health of an organism by removing unwanted or damaged cells in a controlled manner.