cell cycle

• Cells are specialized to work in different levels of organization - skin cells, stomach cells, muscle cells
• Cell cycle


  Cells are either in interphase (growing, replicating DNA, doing cell functions) or M phase (mitosis and cytokenesis)
• Cells spend most of their time in interphase, not dividing
• Checkpoints


  Check that the cell is growing well, replicating DNA correctly, and ready to divide
• If a cell doesn't meet checkpoint requirements

  It can pause to fix the issue, or if it can't be fixed, the cell self-destructs (apoptosis)
• Positive regulators


  Proteins like cyclin and CDK that allow the cell cycle to progress
• Negative regulators


  Proteins like p53 that can initiate apoptosis
• G0 phase


  Resting phase where cells perform functions but don't prepare to divide, some cells stay here permanently like neurons
• Major injuries to the brain or spinal cord can be challenging to heal because many cells in G0 phase can't replicate