Question

COMPARE AND CONTRAST BETWEEN CONTACT INHIBITION AND
SENESCENCE.

Answer 1

Contact inhibition and senescence are both biological phenomena that play significant roles in various cellular processes. However, they have distinct characteristics:

1. **Contact Inhibition:**
- **Definition:** Contact inhibition refers to the phenomenon where cells stop dividing when they come into contact with each other, preventing overcrowding and maintaining tissue integrity.
- **Function:** It ensures controlled cell growth and prevents the formation of tumors. It's crucial for tissue organization during development and wound healing.
- **Mechanism:** When cells are tightly packed, they send signals that inhibit further cell division. This mechanism helps maintain appropriate cell density.

2. **Senescence:**
- **Definition:** Cellular senescence is a state in which cells lose their ability to divide and proliferate due to factors like DNA damage, telomere shortening, or stress.
- **Function:** Senescence contributes to tissue repair and limits the propagation of damaged cells that could potentially become cancerous. It's also associated with aging.
- **Mechanism:** Senescent cells undergo various changes, including altered gene expression, secretion of inflammatory factors, and changes in cell morphology. They remain metabolically active but cannot divide.

In summary, contact inhibition is a mechanism that regulates cell division to prevent overcrowding, while senescence is a state of irreversible cell cycle arrest often triggered by damage or stress. Both processes are important for maintaining tissue homeostasis and preventing uncontrolled growth, but they operate through different mechanisms and have distinct roles in cellular physiology.

Answer 2

Step-by-step explanation:

Contact inhibition of proliferation may be viewed as a reversible form of cell cycle arrest.

Furthermore, to transition from cell cycle arrest to senescence, contact-inhibited cells must activate growth-activating pathways such as mTOR.