Download CELL GROWTH AND DIVISION:

CELL GROWTH
AND DIVISION:
THE CELL CYCLE
Importance of Cell Division
• Growth of organism (adding more cells)
• To replace dead or damaged cells (healing)
Why do cells need to divide?
When cells get too large:
• They can’t get nutrients fast enough
• They can’t get rid of wastes fast
•
enough
The nucleus can’t keep up with the
demands of the cell
Chromosomes
• Coiled DNA and
•
•
protein (has
instructions for the cell
to divide)
Chromatids - identical
copies of information
(sister chromatids)
Centromere - place
where chromatids
attach
TYPICAL CELL DIVISION
(MITOSIS)
*Humans have
46 chromosomes
in each cell
(except sperm
and egg)
46
46
1 CELL
46
Each
cell
has
the
same
#
of
chromosomes
2 IDENTICAL Daughter CELLS
THE CELL CYCLE
Interphase, Mitosis and
Cytokinesis
C
E
L
L
D
I
V
I
S
I
O
N
Interphase
• G1 phase - cell grows in size
• S phase - cell duplicates its chromosomes
(DNA replication)
• G2 phase - cell makes more proteins to
help prepare for cell division
Mitosis
Divided into 4 phases:
• Prophase
• Metaphase
• Anaphase
• Telophase
Prophase
• Nuclear membrane
•
•
•
breaks down
Spindle fibers begin to
form
Centrioles (organelle
involved in cell
division) move apart
Chromatin coils into
chromosomes
(become visible)
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Metaphase
• Chromosomes
•
migrate to the middle
of the cell
Spindle fibers are
attached to the
centromeres
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Anaphase
• Sister chromatids pull
apart and move to
opposite ends of the
cell
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Telophase
• New nucleus forms
•
•
•
around each set of
chromosomes
Cell pinches inward at
center
Chromosomes unwind
into chromatin
Spindle fibers break
down
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Cytokinesis (after mitosis)
• Division of the cytoplasm
•
•
(cell divides in two begins during Telophase)
Plant cells - cell plate
forms (new cell wall)
Animal cells - cleavage
furrow
forms
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
How is the cell cycle
controlled?
Enzymes and other proteins determine:
• When a cell should start dividing
• When a cell should stop dividing
*when these proteins don’t work right or are not
made correctly, cancer can result
CANCER
A disease that results from mutations
(mistakes) in a cell’s DNA which
results in the uncontrolled division of
cells
Tumor - mass of abnormal
cells resulting from rapid cell
division
Types of Tumors
Benign
- mass of abnormal cells which is
not cancerous
Malignant
- mass of cancerous cells that
invade nearby tissues and spread
throughout the body
What do cancer cells do in
the body?
• They starve nearby cells by causing
•
blood vessels to grow into the tumor
to supply it with nutrients
(angiogenesis)
They can metastasize (spread) to the
bloodstream and go to other areas of
the body and grow new tumors
See animation