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Cell Cycle
The life of a cell
• Most cells in the body are called
somatic cells.
• These cells go through a series of
stages called the cell cycle.
• Most of the cell’s life is spent in
interphase, a phase of growth and
normal functioning.
• A portion of its life is spent in cell
division.
• Only happens in eukaryotes
The Cell Cycle
• The four stages of
the cell cycle are:
• G1- A time for
growth
• S- Genetic Material
replicates
• G2- Cell Grows
• M- Cell divides
using mitosis.
Checkpoints
• The cell cycle has a series of checkpoints- cell
cycle control system.
• Checkpoints are controlled by proteins.
• 3 Checkpoints– G1-Checks for normal growth
– G2-Checks for proper DNA synthesis
– M-Checks for proper attachment in mitosis before
cells are pulled apart.
• If any of these checkpoints failapoptosis
(programmed cell death)
How do checkpoints work?
• There are a series of
proteins called cyclindependent kinase.
• These enzymes wait
for a signal from the
cell and then activate
the cell cycle.
• Signal is in the form
of a protein, usually.
Cell Cycle Demo
http://www.cellsalive.com/cell_cycle.htm
What can go wrong?
• At any point in the cycle, the cell could
malfunction.
• If it does not pass a checkpoint, it either
dies or goes into a permanent resting
state.
• If the checkpoint system malfunctions,
cells divide uncontrollablyCancer!