Download We discussed yesterday that cells can*t continue to grow bigger and

We discussed yesterday that cells can’t continue to
grow bigger and bigger. The surface area to volume
ratio becomes too small and diffusion can’t happen
fast enough to meet the demands of the cell.
To solve this problem, a growing cell divides to
form two daughter cells which are identical
copies of the original cell.
•Prior to cell division, the DNA is duplicated to
give each daughter cell a complete copy of
DNA.
•During division, the cytoplasm and organelles
are divided up between the 2 cells. This results
in 2 cells with a smaller volume.
The Cell Cycle
G0- Rest
Mitosis = Division
2 daughter
cells

G2-Growth 2
•The volume of the
cell increases again.
•DNA is checked for
mistakes.
•Mistakes are either
repaired or the cell is
destroyed—Apoptosis
Important note:
G1, S, and G2 together
make what is called
INTERPHASE which
means “between
divisions.”
DNA
 Size
DNA
Size
S- Synthesis
DNA is copied so both
daughter cells will have
a complete set of DNA
•Cells are doing their
job!
•Some cells remain in
rest forever (nerve cells)
others never rest (bone
marrow, skin).
•This cycle is controlled
by proteins called
Cyclins and CDK’s
G1- Growth 1
•The volume increases
as the cell make
organelles and
proteins.
•DNA in the nucleus is
uncoiled because it is
being used to make
proteins and
organelles.