What are mitogens?
They are produced by dividing cells to keep nearby neighboring cells from dividing.
They are extracellular signals that stimulate cell division.
They are transcription factors that induce cell death.
They are kinases that block cell proliferation.
The Correct Answer and Explanation is :
The correct answer is:
They are extracellular signals that stimulate cell division.
Explanation
Mitogens are signaling molecules, typically proteins or peptides, that promote cell division by stimulating cells to progress through the cell cycle. These extracellular signals bind to specific receptors on the surface of target cells and activate intracellular signaling pathways, leading to the expression of genes necessary for cell cycle progression and division.
Mitogens play a critical role in regulating cellular proliferation, especially during growth, development, wound healing, and immune responses. They are particularly important in processes requiring rapid cell multiplication, such as in the repair of damaged tissues or the activation of immune cells during an infection.
The key steps in mitogen-induced cell division include:
- Binding to Receptors: Mitogens bind to cell surface receptors, often receptor tyrosine kinases (RTKs), triggering receptor activation.
- Signal Transduction: This activates downstream signaling cascades such as the MAPK (Mitogen-Activated Protein Kinase) pathway or PI3K-AKT pathway.
- Gene Expression: The signaling pathways lead to the activation of transcription factors like MYC and cyclins, which regulate the expression of genes required for the G1/S transition in the cell cycle.
- Progression Through the Cell Cycle: The cell progresses from the G1 phase to the S phase, where DNA replication occurs, ultimately leading to cell division.
Mitogens are tightly regulated because uncontrolled cell division can result in disorders like cancer. In cancer, some cells acquire mutations that mimic mitogenic signaling, leading to unchecked proliferation.
Misconceptions:
- Mitogens are not transcription factors but extracellular signals that indirectly influence gene transcription.
- Mitogens do not block cell proliferation but instead stimulate it.
- Mitogens are not produced to prevent neighboring cells from dividing, but they may influence local cellular behavior in specific contexts.