CHAPTER 10GROWTH

ANDDIVISION

Cell reproduction is differentin prokaryotes than in eukaryotes.

ProkaryotesLack a nucleusHave a single chromosomeReproduce by binary fission

E. Coli Reproducing by binary fission

EukaryotesHave a nucleus and membrane bound organellesReproduce by mitosis (asexual)

Parent Cell

Daughter cells

In most cases, living things grow by producing more cells.

2 main reasonswhy cells divideare: 1) too large ademand on DNA2) difficulty movingenough materialsacross the cellmembrane

If a cell continuedto grow largerwithout dividing, its DNA would nolonger be able to meet the cell’sneeds

The rate of exchange of materials acrossthe membrane depends on thesurface area of the cell; while the rate at which foodand oxygen are used up and wastes are produced depends on the cell’s volume.

As a cell increases in size, thevolume increases much morequickly than the surface area.this causes problems in moving sufficient materials across the membrane.

Cell division solves the problemof moving enough materials byincreasing the surface area of the cell and solves the problemof insufficient DNA by replicating the chromosomes(making a copy of the DNA).

Before it becomes too large, agrowing cell divides formingtwo “daughter” cells in theprocess called cell division.

CELL CYCLE

Phases of the Cell CycleG1 phaseS (synthesis) phaseG2 phaseM phase (mitosis)

G1, S, and G2 are collectivelycalled Interphase.

INTERPHASE

G1 PHASEFirst growth stageCell increases in sizeSynthesize new proteins and

organelles

DNA molecules are synthesizedChromosomes duplicated

S phase

Time between DNA synthesis & mitosis

Cell continues growingNeeded proteins and organelles produced

G2 phase

M PHASECell growth & protein production stop

Cell’s energy used to make 2 daughter cells

Called mitosis or karyokinesis (nuclear division)

Only occurs in eukaryotes

M phase orMitosis is Divided into4 sub phases:ProphaseMetaphaseAnaphaseTelophase

CELLS UNDERGOING MITOSIS

ProphaseLongest phaseChromosomes become visibleCentrioles move to poles of cellNuclear membrane breaks down

Nucleolus disappearsChromosomes attach to spindle at centromere

23Nucleus & Nucleolus have disintegrated

Chromosomes

Chromosomes

Nucleolus Cytoplasm

Nuclear Membrane

HUMAN CHROMOSOMES

MetaphaseChromosomes line up along equator of cellMicrotubules connect centromeres to pole of spindle

METAPHASE

STEPS IN ANAPHASE

Chromosomes are separated Spindle fibers shorten so chromosomes are pulled to poles of cell

MITOTIC SPINDLE

ANAPHASE

STEPS IN TELOPHASE Separation of chromosomes completed Cell plate forms (plants) Cleavage furrow forms(animals) Nucleus & nucleolus reform Chromosomes uncoil

TELOPHASE

       Plant             Animal

CYTOKINESIS

Occurs after chromosomes separate

Forms two, identical daughter cells

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CYTOKINESISCleavage furrow in animal cell

Cell plate in plant cell

NO. ALL CELLS DO NOT MOVE THROUGH THE CELL CYCLE AT THE SAME RATE.MUSCLE CELLS AND NERVE CELLS DO NOT DIVIDE ONCE THEY HAVE DEVELOPED.51. SKIN, DIGESTIVE TRACT, AND BONE MARROW CELLS DIVIDE RAPIDLY THROUGHOUT LIFE.

YES. THE CONTROLS ON CELL GROWTH AND CELL DIVISION CAN BE TURNED ON AND OFF.

THE PROCESS OF CELL DIVISION IS TURNED ON WHEN AN INJURY OCCURS. THE CELLS AT THE EDGE OF THE INJURY ARE STIMULATED TO DIVIDE RAPIDLY.

CANCER IS A DISORDER IN WHICH SOME OF THE BODY’S OWN CELLS LOSE THE ABILITY TO CONTROL GROWTH.

CANCER CELLS DO NOT RESPOND TO THE SIGNALS THAT REGULATE THE GROWTH OF MOST CELLS. CANCER CELLS DIVIDE UNCONTROLLABLY AND FORM MASSES OF CELLS CALLED TUMORS. TUMORS ARE HARMFUL BECAUSE THEY DAMAGE SURROUNDING TISSUES.

CANCER MAY BE CAUSED BY TOBACCO, RADIATION, OR VIRAL INFECTION.

ALL CANCERS HAVE ONE THING IN COMMON: THE CONTROL OVER THE CELL CYCLE HAS BROKEN DOWN.

A LARGE NUMBER OF CANCER CELLS HAVE A DEFECT IN THE P53 GENE. THE P53 GENE NORMALLY HALTS THE CELL CYCLE UNTIL ALL CHROMOSOMES HAVE BEEN REPLICATED.

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MITOSIS ANIMATIONName each stage as you see it occur?

41

TEST YOURSELF OVER MITOSIS

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MITOSIS QUIZ

43

NAME THE STAGES OF MITOSIS:

Interphase

Early prophase

Mid-ProphaseLate Prophase

Metaphase

Late Anaphase

Early Anaphase

Early Telophase, Begin cytokinesis

Late telophase, Advanced cytokinesis

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IDENTIFY THE STAGES

Early, Middle, & Late Prophase

Late ProphaseMetaphase Anaphase

Late Anaphase Telophase Telophase & Cytokinesis

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45

LOCATE THE FOUR MITOTIC STAGES IN PLANTS

Metaphase

Prophase

Anaphase

Telophase