Mechanism

Question 1

What are the two opposite sets of signals that determine the survival or apoptosis of cells?

Answer 1

The two opposite sets of signals that determine the survival or apoptosis of cells are death signals (proapoptotic) and prosurvival (anti-apoptotic) signals

Question 2

How is apoptosis different from necrosis?

Answer 2

Apoptosis is different from necrosis because
apoptosis is a highly regulated process that engages the cell’s own signaling cascades and results in the cell’s own death (suicide).
In contrast, necrosis is an uncontrolled form of cell death that is often triggered by external factors such as injury or infection.

Question 3

What is the role of caspases in apoptosis

Answer 3

Caspases are enzymes that cleave proteins after aspartic residues and play a crucial role in apoptosis. They are activated by proapoptotic signals and cleave specific proteins, leading to the breakdown of the cell’s structure and function

Question 4

What are proapoptotic signals and where do they come from

Answer 4

Proapoptotic signals can come from external sources such as cytokines or toxins or from internal signals such as DNA damage. These signals activate caspases, leading to apoptosis.

Question 5

Give some examples of anti-apoptotic signals.

Answer 5

Examples of anti-apoptotic signals include growth factors, cytokines, and certain cellular pathways. These signals act to inhibit caspase activation and promote cell survival

Question 6

Why is the balance between proapoptotic and anti-apoptotic signals important for maintaining tissue homeostasis

Answer 6

The balance between proapoptotic and anti-apoptotic signals is important for maintaining tissue homeostasis because excessive cell death or cell survival can lead to disease progression. The regulation of apoptosis is essential for tissue development, immune system function, and the prevention of cancer

Question 7

Define apoptosis

Answer 7

Apoptosis is a type of (programmed) cell death induced by
a tightly regulated suicide program. It is characterized by
activation of intrinsic enzymes of the cell that degrade its
own nuclear DNA and proteins (nuclear and cytoplasmic).

Question 8

Physiological Situations

Answer 8

Removal of excess cells during embryogenesis and
developmental processes: For example, disappearance
of web tissues between fingers and toes.
• Elimination of cells after withdrawal of hormonal
stimuli: For example, endometrial cell breakdown during
the menstrual cycle.
Elimination of cells after withdrawal of tropic stimuli:
For example, neutrophils in an acute inflammatory
response, lymphocytes after immune response.
• Elimination of potentially harmful cells: In immunology,
the clones of self-reactive lymphocytes that recognize
normal self antigens are deleted by apoptosis.