Lecture Notes on Cell Cycle and Cell Division

Introduction

• Curiosity about cell activity while in class.
• Cell theory: All living things are made of one or more cells.
  • Multicellular organisms have cells that work together in tissues, organs, and systems.

Specialized Cells

• Types of cells: skin cells, stomach cells, muscle cells, etc.
• Functions are regulated by the cell cycle.

Cell Growth and Reproduction

• Multicellular organisms grow by increasing the number of cells, not by enlarging existing ones.
• Cell reproduction involves mitosis and cytokinesis.
  • Necessary to understand why we grow.

Cancer and Cell Division

• Cancer results from uncontrolled cell division.
  • Cells divide too frequently, leading to cancer.
• Cancer cell characteristics:
  • Poor communication with healthy cells.
  • Inability to perform normal functions.
  • May secrete growth hormones that divert nutrients.
• Causes: Genetic links, exposure to toxins, radiation, excessive UV light.
• Treatments: Radiation and chemotherapy target frequently dividing cells.

The Cell Cycle

• Represented as a pie chart.
  • Phases: Interphase and M phase.
• Interphase: Cells grow, replicate DNA, perform functions.
• M Phase: Mitosis and cytokinesis, where actual cell division occurs.

Mitosis Frequency

• Hair follicle cells divide frequently (related to hair growth and chemotherapy side effects).

Checkpoints in the Cell Cycle

• Ensure cells do not divide with errors.
• Key Phases:
  • G1: Growth and resource check.
  • S Phase: DNA synthesis.
  • G2: Preparation for mitosis.
  • M Phase: Metaphase checkpoint for chromosome alignment.

Consequences of Failing Checkpoints

• Possible cell pause for repairs.
• Irreparable damage leads to apoptosis (cell self-destruction).

Regulation of the Cell Cycle

• Proteins play a key role in regulation.
• Positive regulators (e.g., Cyclin and CDK) and negative regulators (e.g., p53).
  • CDK is a kinase enzyme; works with cyclin.

G0 Phase

• Resting phase where cells are not preparing to divide.
• Some cells stay here temporarily; others, like neurons, may stay permanently.
  • Implications for healing, particularly in brain and spinal cord injuries.

Conclusion

• Encouragement to explore the topic further.
• Stay curious about cellular functions.