Download 5.1 Cell Cycle

5.1 Cell Cycle
Chapter 5 Cell Growth and Division and Growth
Mr. Shilala
DAHS
KEY CONCEPT
Cells have distinct phases of growth, reproduction,
and normal functions.
The cell cycle has four main stages:
gap 1, synthesis, gap 2, and mitosis..
• The cell cycle is a regular
pattern of growth, DNA
replication, and cell division.
• Stages get their name from early
observations
– Interphase when a cell was not
dividing
• Improvements in technology
led interphase being called
– Gap 1,DNA synthesis and
Gap 2
• Realized during interphase
cells carry out normal
functions and grow
– Mitosis when a cell was dividing
Stages of Cell Cycle
1. Gap 1 (G1):
– Cell growth and
normal functions
– Cell Spends majority of
time here
– Varies by type of cell
– Must pass a critical
checkpoint before
going to synthesis
stage
• Like passing a physical
before participating in
sports
2. DNA Synthesis (S)
– Cell copies DNA
– Cell now contains 2
identical copies of
DNA
3. Gap 2 (G2):
– Additional growth
– Cell is getting ready to
divide
– Also contains critical
checkpoint
• Undamaged DNA etc
4. Mitosis – division of
cell nucleus
– Two processes
• Mitosis
• Cytokinesis – cytoplasm
splitting
– Occurs only if the cell is large
enough and the DNA
undamaged
Cells divide at different rates.
• The rate of cell division varies widely with
the need for those types of cells.
G0 Stage
• Stage when a cell
reaches a point where
it is highly unlikely to
divide
– Example: Neuron in
spinal cord
– Lymphocytes – divide
only when invader
enters body
Cell size is limited and determined by
the SA to V ratio.
• Cells have upper and lower limits
• Determined by the surface area to Volume
ratio.
• Surface area must allow for
adequate exchange of
nutrients.
– Cells that must be large have
unique shapes
• To maintain a suitable size
cells divide
• To maintain a suitable
size cells must divide
– Must be coordinated
• Example
– If a cell doubles in size
before dividing,
daughter cells will be
twice as large as
original cell –
eventually cells too
large to survive