Lecture Notes: Understanding Cells and the Cell Cycle

Introduction to Cells

• Every living organism is made up of cells.
• Cells form tissues, tissues form organs, and organs form organ systems.
• Different types of cells: skin cells, stomach cells, muscle cells, etc.
• Cells are regulated through the cell cycle.

Cell Cycle and Growth

• Multicellular organisms grow by producing more cells, not by enlarging existing cells.
• Cell reproduction involves mitosis and cytokinesis.
• Controlled cell division is crucial; uncontrolled division can lead to cancer.

Cancer and Cell Regulation

• Cancer involves cells dividing too frequently and uncontrollably.
• Cancer cells may:
  • Fail to communicate with healthy cells.
  • Fail to anchor properly, leading to metastasis.
  • Secrete growth hormones diverting nutrients.
• Risk factors include genetic links, exposure to toxins, radiation, and UV light.
• Treatments include radiation and chemotherapy, targeting frequent cell division.

The Cell Cycle: Phases and Checkpoints

• The cell cycle is typically depicted as a pie chart.
• Interphase:
  • Cells grow, replicate DNA, and perform standard functions.
• M Phase:
  • Involves mitosis and cytokinesis (cell division).
• Most cells spend time in interphase rather than dividing.

Stages in Interphase

• G1 Phase:
  • Cell growth.
  • Checkpoints ensure DNA is undamaged and resources are adequate.
• S Phase:
  • DNA replication (S for Synthesis).
• G2 Phase:
  • Further cell growth in preparation for mitosis.

Checkpoints in the Cell Cycle

• Ensure cells are ready to progress to the next phase.
• Errors or damage can halt progress; if unfixable, apoptosis occurs (cell self-destruction).

Regulation of the Cell Cycle

• Proteins regulate cycle progression:
  • Cyclins and CDKs:
    • Cyclins bind to CDKs and fluctuate through the cycle.
    • Each phase involves different cyclin-CDK activity.
  • p53:
    • Negative regulator, can initiate apoptosis.

G0 Phase

• Resting phase where cells perform functions but do not divide.
• Some cells enter temporarily, others (e.g., neurons) may remain permanently.
• Challenges in healing brain/spinal cord injuries due to cells in G0.

Conclusion

• The regulation of cell division is crucial for organism growth and preventing diseases like cancer.
• Encouragement to explore more about the impact and regulation of the cell cycle.

Remember to explore further on topics like the role of CDKs, the significance of apoptosis, and ongoing research in cell biology.