Cell Cycle and Cancer: Key Points

Introduction

• Cells are fundamental units of life; all living things are made of cells.
• Multicellular organisms have specialized cells working together in tissues, organs, and organ systems.
• Regulation of cell functions is essential.

Growth and Cell Division

• Organisms grow through cell reproduction, not by individual cell enlargement.
• Mitosis allows the division of cells to create new body cells.
• Unregulated cell division can lead to cancer.

Cancer and Uncontrolled Cell Growth

• Cancer involves cells that divide uncontrollably.
• Characteristics of cancer cells:
  • Poor communication with healthy cells
  • Inability to perform normal functions
  • Lack of secure anchoring
  • Some can secrete growth hormones, diverting nutrients from healthy cells
• Risk factors for cancer:
  • Genetic predisposition
  • Exposure to toxins, radiation, or UV light
• Tumors can be benign (stay put) or malignant (spread).

Cell Cycle Overview

• The cell cycle consists of two main phases:
  • Interphase: Cells grow, replicate DNA, and perform functions
  • M Phase: Mitosis and cytokinesis occur
• Most of the time, cells are in interphase.

Phases of Interphase

1. G1 (Gap 1): Cell growth and preparation for DNA replication
2. S (Synthesis): DNA replication occurs
3. G2 (Gap 2): Further cell growth and preparation for mitosis

Checkpoints in the Cell Cycle

• G1 Checkpoint:
  • Checks cell growth, DNA damage, and resources
• G2 Checkpoint:
  • Ensures DNA was replicated correctly and checks resources
• M Phase Checkpoint:
  • Ensures chromosomes are aligned and attached properly for separation

Response to Checkpoint Failure

• If a cell fails a checkpoint and the issue is fixable, it may pause.
• If not fixable, the cell undergoes apoptosis (self-destruction) to avoid dividing with damage.

Regulation of the Cell Cycle

• Proteins regulate the cell cycle:
  • Positive Regulators: Allow progression (e.g., cyclin and Cdk)
  • Negative Regulators: May stop cell cycle (e.g., p53 initiates apoptosis)
• Different cyclins bind to Cdk at different phases, influencing cell cycle progression.

G0 Phase

• G0 Phase: Resting state where some cells perform functions but do not prepare to divide.
• Some cells, like neurons, may remain in G0 permanently, affecting healing after injury.

Conclusion

• The cell cycle and its regulation are crucial areas of research, especially concerning cancer.
• Stay curious and explore beyond this material.