Cell Growth & Division
10-1 Cell Growth
Limits to cell growth
10-1 Cell Growth
DNA overload
When a cell is small, its DNA is able to meet
all of the cell’s needs.
As the cell grows it
produces more organelles,
but the DNA is not
replicated and it cannot
meet the cell’s needs.
10-1 Cell Growth
Exchanging
materials
The rate at which food and oxygen
are used up and waste products are
produced depends on the cell’s
volume.
As the cell grows it becomes more
difficult for it to get rid of wastes and
to get food and oxygen into the
cell.
10-1 Cell Growth
Ratio of surface area to volume
Imagine a cell that is shaped like a cube.
The surface area of a cell would be equal to
length x width x number of sides(6) of a cell.
The volume of the cell would be equal to
length x width x height of the cell.
The volume of the cell increases more
rapidly than the surface area.
10-1 Cell Growth
Example
Cell size
Surface
area
volume
Ratio of surface
area to volume
10-1 Cell Growth
Division of the cell
The process by which a cell
divides into two new daughter
cells is called cell division.
Before the cell divides, it
replicates all of its DNA.
This process reduces cell volume
and solves the DNA overload
problem.
Division of the cell – Cell growth
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
Chromosomes
The information that is passed
from one generation to the next
is carried by chromosomes.
They are made up of DNA and
proteins
A chromosome consists of two
sister chromatids.
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
Cell cycle
The G1, S and G2 phases
are part of the interphase in
the cell cycle.
The cell cycle is divided
into four phases, which are:
G1 phase: the cell
grows
S phase: DNA is
replicated
G2 phase: The cell
prepares to divide
M phase: mitosis
and cytokinesis
10-2 Cell Division
10-2 Cell Division
Back
Prophase
Anaphase
Metaphase
•Telophase
Cell Cycle
Cytokinesis
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
Prophase
During prophase,
the chromosomes
become visible. The
centrioles take
positions in opposite
sides of the cell and
form the spindle.
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
Metaphase
During metaphase,
the chromosomes line
up across the center
of the cell.
Microtubules connect
the centromere of
each chromosome to
the two poles of the
spindle.
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
Anaphase
During Anaphase, the
centromeres that joined the sister
chromatids split becoming
individual chromosomes.
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
Telophase
The chromosomes
move to opposite
sides of the cell and
a nuclear envelope
forms around each
group of
chromosomes.
10-2 Cell Division
10-2 Cell Division
Cytokinesis
The process in which the
cytoplasm separates, forming
completely the two new daughter
cells.
It usually occurs about the same
time as Telophase.
This occurs different in plants and
in animals.
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
10-2 Cell Division
Animals
The cell membrane is drawn inwards
until the cytoplasm is pinched into
two nearly equal parts.
Each part contains its own nucleus
and cytoplasmic organelles.
10-2 Cell Division
Plants
A structure known as the cell
plate forms midway between
the divided nuclei.
The cell plate gradually
develops into a separating
membrane.
A cell wall then begins to
appear in the cell plate.
10-3 Regulating the Cell Cycle
Regulating the Cell
Cycle
10-3 Regulating the Cell Cycle
10-3 Regulating the Cell Cycle
10-3 Regulating the Cell Cycle
10-3 Regulating the Cell Cycle
10-3 Regulating the Cell Cycle
If center cells are removed,
cells near the space will
start to grow again.
Cells grow until they
touch other cells
SHOWS: Cell division
genes can be turned on
and off
10-3 Regulating the Cell Cycle
CELL CYCLE REGULATORS
In early 1980’s scientists discovered a
protein in dividing cells that caused a
Mitotic spindle form in
_________________to
NON-dividing
_______________ cells
10-3 Regulating the Cell Cycle
CELL CYCLE REGULATORS
Levels of this protein rose and fell with
the cell cycle so it was named
CYCLIN
__________ because it seemed to
control the cell cycle.
A whole family of
CYCLINS have since been
discovered that regulate the
TIMING
of CELL CYCLE
_____________________
in EUKARYOTIC CELLS
10-3 Regulating the Cell Cycle
OTHER REGULATORS
______________
INTERNAL REGULATORS
Proteins that respond to events inside
the cell.
Allow cell cycle to proceed only if
certain processes have happened
EX: Cell can’t enter mitosis until all the
chromosomes have been copied
10-3 Regulating the Cell Cycle
OTHER REGULATORS
EXTERNAL REGULATORS
______________
Proteins that respond to events outside
the cell.
Signals tell cell to speed up or slow
down the cell cycle
EX:
Growth factors stimulate cells to divide
Especially important during
wound healing and
embryo development
10-3 Regulating the Cell Cycle
EXTERNAL REGULATORS
Molecules on the surface of neighboring
cells act as signals to slow down
or stop the
cell’s cycle.
These signals prevent
excessive growth and
keep tissues from
disrupting each other.
10-3 Regulating the Cell Cycle
SEM Image by: Riedell
10-3 Regulating the Cell Cycle
NO CONTACT INHIBITION
Cancer cells don’t stop
when they touch nearby
cells. . .
they just keep growing!
That’s what makes
a tumor.
http://www.exn.ca/news/images/2000/08/02/20000802-cancer.jpg
10-3 Regulating the Cell Cycle
Carcinogens
10-3 Regulating the Cell Cycle
CELL CYCLE
p53