Biology
Ch. 10
Cell Growth and Division
Core Content: SC-HS-3.4.3
10–1 Cell Growth
A. Limits to Cell Growth
1.
DNA “Overload”
2.
Exchanging Materials
3.
Ratio of Surface Area to Volume
4.
Cell Division
Limits to Cell Growth
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The larger a cell becomes, the more
demands the cell places on its DNA.
The cell has “DNA overload”, and the
needs of the growing cell can no
longer be met.
The more trouble a cell has moving
enough nutrients and wastes across
the cell membrane.
Surface area to Volume Ratio
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As a cell grows, the volume of the cell
increases faster than the surface area.
The resulting decrease in the cell’s
ratio of surface area to volume makes
it difficult for the cell to move needed
materials in and waste products out.
Ratio of Surface Area to
Volume in Cells
Cell Size
Cell Size
Surface Area
(length x width x 6)
Surface Area
(l x w x 6)
Volume
(l x w x h)
Surface area to
Volume ratio
10–2
A.
B.
C.
D.
Cell Division
Chromosomes
The Cell Cycle
Events of the Cell Cycle
Mitosis
1.
Prophase
2.
Metaphase
3.
Anaphase
4.
Telophase
E. Cytokinesis
Cell Division
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Before it becomes too large, a growing cell
must divide into two “daughter” cells. This
is cell division.
Before cell division occurs, the cell copies its
DNA. This ensures that each daughter cell
gets a complete set of genetic information.
Division increases the cell’s surface area to
volume ratio.
Chromosomes
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Chromosomes are made of DNA, which
carries the cell’s coded genetic information,
and proteins.
Cells of each organisms have a specific
number of chromosomes. Ex) humans have
46
Chromosomes are not visible except during
cell division.
Each chromosome consists of two identical
“sister” chromatids that are attached at
the centromere.
The Cell Cycle
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During the cell cycle, a cell grows,
prepares for division, and divides to
form two new daughter cells.
Interphase is the period between
divisions, and includes G1, S, and G2
phases.
The M phase follows interphase, and
includes mitosis and cytokinesis.
Concept Map
Section 10-2
Cell Cycle
includes
G1 phase
Interphase
M phase
(Mitosis)
is divided into
is divided into
S phase
G2 phase
Prophase
Metaphase
Anaphase
Telophase
Interphase
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Interphase takes much longer than actual
cell division.
G1: Cells do most of their growing. Cells
increase in size and synthesize new proteins
and organelles.
S: DNA is copied
G2: Cell prepares for mitosis, makes
organelles and structures needed for cell
division
Figure 10–4 The Cell Cycle
Section 10-2
G1 phase
M phase
S phase
G2 phase
Go to
Section:
Mitosis
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Following the events of Interphase,
the cell will begin to divide. This is
mitosis.
Biologists divide mitosis into four
phases: prophase, metaphase,
anaphase, and telophase
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Prophase
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The first and longest phase of mitosis
is prophase.
During prophase, the chromatin
condenses to form chromosomes.
The centrioles separate, and a spindle
begins to form.
The nuclear membrane breaks down.
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Metaphase
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The stage following prophase is
metaphase.
During metaphase, the chromosomes
line up across the center of the cell.
Each chromosome is connected to a
spindle fiber at its centromere.
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Anaphase
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Following metaphase is anaphase.
During anaphase, the sister
chromatids separate into individual
chromosomes and are moved apart.
The chromosomes form groups near
the poles of the spindle.
Anaphase ends when the
chromosomes stop moving.
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Telophase
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The fourth and final stage of mitosis is
telophase.
The chromosomes gather at opposite
ends of the cell, and lose their distinct
shapes.
Two nuclear membranes begin to
form.
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Cytokinesis
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Cell division is not complete until cytokinesis
occurs. Cytokinesis is division of the
cytoplasm.
In animal cells, the cell membrane is drawn
inward until the cytoplasm is pinched into
two equal parts.
In plants, a cell plate forms midway
between the divided nuclei. The cell plate
gradually develops into a separating
membrane.
Cleavage furrow in
animal cells
Cell plate forming in plant
cell
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9–3 Regulating the Cell Cycle
A. Controls on Cell Division
B. Cell Cycle Regulators
1.
Internal Regulators
2.
External Regulators
C. Uncontrolled Cell Growth
Cell Cycle Regulators
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Cyclins regulate the timing of the cell cycle
in eukaryotic cells.
Proteins that respond to events inside the
cell are called internal regulators.
Proteins that respond to events outside the
cell are called external regulators.
Most cells grow until they come in contact
with other cells, then they stop (contact
inhibition).
Control of Cell Division
Section 10-3
Figure 10–8 Effect of Cyclins
A sample of
cytoplasm is
removed
from a cell in
mitosis.
A sample is
injected into a
second cell in
G2 of
interphase.
As a result, the
second cell
enters mitosis.
Uncontrolled cell growth
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Cancer cells do not respond to the signals
that regulate the growth of most cells.
A defect in a gene called p53 has been
found in many types of cancer cells.
They continue to grow out of control, and
can form masses of cells called tumors.
Tumors can damage surrounding tissues.
Benign vs. Malignant tumors
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If the abnormal cells remain at the
original site, the tumor is BENIGN
and can usually be surgically
removed.
If the tumor invades other organs
and impairs their function, the
tumor is MALIGNANT.
The spreading of cancer cells is
METASTASIS.
BREAST CANCER
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BREAST CANCER CELL
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NORMAL
MAMMOGRAM
CANCEROUS
MASS
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Apoptosis
– Programmed cell death.
– Usually shrink and shrivel in a controlled
process.
– Example: development of hands and feet.
Your hands and feet have webbing
between them in utero. But when a baby
is born this webbing is gone because of
apoptosis.
– Example: leaves falling off trees and
plants in autumn.
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Stem Cells
– Unspecialized cells that can develop into
specialized cells when under the right
conditions.
– Two types: Embryonic and adult stem
cells.
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Embryonic—after fertilization the resulting
mass of cells divides rapidly until there are
about 100-150 cells. These are cells that
have not become specialized yet and can be
used to repair damaged cells in others but is
highly controversial.
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Adult stem cells—found in various
tissues in the body and might be used
to maintain and repair the SAME kind
of tissue in which they are found.