Lecture on Cell Cycle and Cancer

Introduction

• The Amoeba Sisters introduce the concept of cell activity and the cell cycle.
• All living organisms are made of cells; multicellular organisms have specialized cells (e.g., skin, stomach, muscle cells) organized into tissues and organs.
• Importance of cell regulation via the cell cycle.

Cell Growth and Reproduction

• Cells can grow in size but multicellular organism growth is due to cell division.
• Mitosis and cytokinesis are processes that allow for new body cell creation.

Cancer and Cell Division

• Cancer involves uncontrolled cell division.
• Cancer cells divide too frequently and lack regulation.
• Issues with cancer cells:
  • Poor communication with healthy cells
  • Inability to perform normal functions
  • Lack of secure anchoring leading to potential spread
  • Secretion of their own growth hormones, diverting nutrients from healthy cells
• Causes of cancer:
  • Genetic links and family history
  • Toxins, radiation, and UV light exposure
• Tumors can form from uncontrolled growth, some remain localized while others spread.
• Treatments include radiation and chemotherapy, targeting frequently dividing cells.

The Cell Cycle

• Cell cycle is often depicted as a pie chart with two main phases:
  • Interphase: Cells grow, replicate DNA, and perform functions.
  • M Phase: Includes mitosis and cytokinesis, where cell division occurs.
• Most cells spend time in interphase, not dividing.
• Cells’ division frequency varies; e.g., hair follicle cells divide frequently.

Checkpoints in the Cell Cycle

• Importance of checkpoints to ensure proper division:
  • G1 Checkpoint: Assesses cell growth, DNA integrity, and resources.
  • G2 Checkpoint: Ensures DNA replication accuracy and resource availability.
  • M Phase Checkpoint: Ensures chromosomes are aligned and attached correctly.
• If checkpoints are not met and issues can't be fixed, cells undergo apoptosis (self-destruction).

Regulation of the Cell Cycle

• Proteins play a key role in regulation, including:
  • Cyclin and Cdk (Cyclin-dependent kinase): Positive regulators that move cell cycle forward.
  • p53: Negative regulator that can initiate apoptosis.
• Cyclin levels rise and fall with signals, coordinating the cell cycle's phases.

G0 Phase

• Some cells enter G0, a resting phase where they perform functions but do not prepare for division.
• Cells can be temporarily or permanently in G0, such as many neurons in the brain and spinal cord.
• Cells in permanent G0 cannot participate in M phase, impacting recovery from injuries.

Conclusion

• Encouragement to explore the topics further and continue learning.