Cell Growth and Division Chapter 10 By the time you finish reading this sentence, 50 million of your cells will have died and been replaced by others.

Cell Growth and Cell Growth and DivisionDivision

Chapter 10

By the time you finish reading this By the time you finish reading this sentence, 50 million of your cells sentence, 50 million of your cells will have died and been replaced will have died and been replaced by others. Some are lost through by others. Some are lost through 'wear and tear’, some just reach 'wear and tear’, some just reach the end of their life, and others the end of their life, and others deliberately self-destruct.deliberately self-destruct.

A. Importance of Cell A. Importance of Cell Growth and DivisionGrowth and Division

Allows for an organism’s growth

Replaces damaged cells

Allows cells to maintain the proper surface area-to-volume ratio

WHY CAN’T A CELL JUST KEEP GETTING WHY CAN’T A CELL JUST KEEP GETTING BIGGER?BIGGER?

HOWEVER>>>>The larger a cell becomes, the more demands it places on it’s DNA. It also has more trouble moving nutrients and wastes across the cell membrane.

Allows cells to maintain the proper Allows cells to maintain the proper surface area-to-volume ratiosurface area-to-volume ratio

1. Cells cannot simply grow by increasing in size.

Cells of adults and children of a species are the same size.

• The Cell membrane determines the surface area of the cell.

• The volume of a cell is determined by the amount of cytoplasm present with all its contents.

• As a cell’s size increases, its volume increases much faster than its surface area.

The cell overcomes these problems through the process of cell division.

Ratio of Surface Area to Ratio of Surface Area to Volume  Volume    

As the size of a cell increases, its volume increases faster than the surface area.

The decrease in the cell’s ratio of surface area to volume makes it more difficult for the cell to move needed materials in and waste products out quickly enough for the cell to survive.

Find surface area

Find surface area

Find surface area

Find surface area

Find Volume

Find Volume

Find Volume

Find Volume

Find Ratio

Find Ratio

Find Ratio

Find Ratio

How do little elephants grow up to be BIG elephants?

Why do animals shed their skin?

Cell Division!Cell Division!More next time!More next time!

Quiz over Ch 10.1 Cell Growth Next Time

Regulating Cell Division (Cell Regulating Cell Division (Cell Cycle)Cycle)

Cells stop growing when they come in contact with each other-such as when a wound is healing

Cyclins-proteins within the cell that regulate the timing of eukaryotic cell division

a. Internal Cyclins-usually controls cell division events inside the cell like the beginning and end of cell cycle stages.

b. External Cyclins -for events outside the cell. These usually speed up or slow down the cell cycle and heal wounds.

CANCERCANCEROccurs when cells do not respond to normal signals that regulate growth

*Most cancer cells have defect in the p53 gene

Benign Tumor-a tumor that only grows in one place. Noninvasive and usually treatable

Malignant Tumor-invasive uncontrolled growth of cells

Skin Cancer

Cell Division!Cell Division!

Ch 10.2Ch 10.2

Cell ReproductionCell Reproduction

ProkaryotesBacteria

EukaryotesPlants &

animals

ProkaryotesProkaryotes

Lack a nucleus Have a single chromosomeReproduce asexually by

binary fission Include bacteria

Steps in Binary FissionSteps in Binary Fission

1. Cells increase their cell mass slightly

2. DNA & cell components are replicated

3. Each cell divides into 2 daughter cells

Binary Fission of Bacterial Binary Fission of Bacterial CellCell

E. Coli E. Coli Dividing by Binary Dividing by Binary FissionFission

EukaryotesEukaryotes

Contain a nucleus & membrane bound organelles

Asexually reproduce cells by mitosis

VocabularyVocabularyMitosisMitosis = division of the cell nucleus and

its contentsCytokinesisCytokinesis = the division of cell

cytoplasm into two identical daughter cells

ChromatinChromatin = the combination of DNA and histone proteins

Chromosome-main organelle involved in Cell Cycle

DiploidDiploid = Two copies of each chromosome, one paternal, one maternal

ChromosomChromosomeses

in the in the Larger Larger SchemeScheme

Chromosome Chromosome StructureStructure

1 – Chromatid-because each has an identical half they are “sister” chromatids

2 – Centromere3 – Short arm4 – Long arm

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ChromosomesChromosomes

Made from DNA– Genetic material

directs activities determines characteristics

Formed from chromatin– Uncoiled DNA

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Chromosomes Chromosomes (cont.)(cont.)

Each chromosome (at this point) is made up of 2 identical chromatids

– Joined strands of identical duplicated genetic material

Joined at centromere

– Chromatids separate and each cell has identical information

Formed in S phase of cell cycle

From: http://www.rothamsted.bbsrc.ac.uk/notebook/courses/guide/chromo.htm

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From: http://www.accessexcellence.org/RC/VL/GG/nucleosome.html

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Sets of chromosomesSets of chromosomes

Each human somatic (body) cell – 23 pairs of chromosomes (46 total)

Homologous chromosomes– Each pair is called homologous

Similar in size, shape and genetic content Not identical! One from each parent

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Cell Cycle Interphase

– G1 - growth and normal cell activity G0 – never divides again

– S - Synthesis of DNA DNA replication

– G2 - Growth for division, organelles double

Mitosis - Division of the nucleus Cytokinesis - Division of the cytoplasm (cell)

Cell CycleCell Cycle

Stages in growth & division

G1 Phase S Phase G2 Phase M Phase Cytokinesis

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1/ 25/ 01

Page: 5

Cell cycleCell cycle

G0

Growth & normal cell activity

DNA replication

Growth for divisionOrganelles double

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Length of cell cycleLength of cell cycle

Ranges from 20 minutes to 20 hoursSome cells divide constantly and others

never divide– Muscle cells– Red Blood cells– Skin cells– Bone cells– Nerve cells

G1 PhaseG1 Phase

First growth stageCell increases in sizeCell prepares to copy its DNA

Synthesis (S) PhaseSynthesis (S) Phase

Copying of all of DNA’s instructions

Chromosomes duplicated

G2 PhaseG2 Phase

Time between DNA synthesis & mitosis

Cell continues growingNeeded proteins produced

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MitosisMitosisA process in which eukaryotic cells form

two identical nuclei.– Each cell receives a complete set of

chromosomes– division of the nucleus

Cytokinesis– division of the cytoplasm

2 independent cells (genetically identical)

– Different in plant and animals

Significance of the process of mitosis

M PhaseM Phase

Cell growth & protein production stop

Cell’s energy used to make 2 daughter cells

Called mitosis or karyokinesis (nuclear division)

Life Cycle of a CellLife Cycle of a Cell

Mitosis is a cycle with no beginning or end.

Interphase – Resting StageInterphase – Resting Stage

Cells carrying on normal activities

Chromosomes aren’t visibleCell metabolism is occurringOccurs before mitosis

InterphaseInterphase

D. Stages of MitosisD. Stages of Mitosis

ProphaseMetaphaseAnaphaseTelophase

Major Events in MitosisMajor Events in Mitosis

Cells Undergoing MitosisCells Undergoing Mitosis

Steps in ProphaseSteps in Prophase1. DNA coils tightly & becomes

visible as chromosomes2. Nuclear membrane disappears3. Nuceolus disappears4. Centrioles migrate to poles5. Spindle fibers begin to form

and the chromosomes attach

Eukaryotic ChromosomeEukaryotic Chromosome

Spindles attach here

ProphaseProphase

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Spindle fibers

Centrioles

Steps in MetaphaseSteps in Metaphase

Spindle fibers from centrioles attach to each chromosome

Cell preparing to separate its chromosomes

Cell aligns its chromosomes in the middle of the cell

MetaphaseMetaphase

MetaphaseMetaphase

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Steps in AnaphaseSteps in Anaphase

Cell chromosomes are separated

Spindle fibers shorten so chromosomes pulled to ends of cell

Mitotic SpindleMitotic Spindle

AnaphaseAnaphase

AnaphaseAnaphase

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

Steps in TelophaseSteps in Telophase Separation of

chromosomes completed

Cell Plate forms (plants)

Cleavage furrow forms(animals)

Nucleus & nucleolus reform

Chromosomes uncoil

TelophaseTelophase

       Plant             Animal

TelophaseTelophase

Animal Cell Plant Cell

Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm

CytokinesisCytokinesis

Occurs after chromosomes separate

Forms two, identical daughter cells

CytokinesisCytokinesis

Cell Plate Forming in Plant Cells

Animal Mitosis -- Review

Interphase

Prophase

Metaphase

Anaphase

Telophase

Interphase

Plant Mitosis -- ReviewInterphase

Prophase

Metaphase

Anaphase

Telophase

Interphase

04/18/23 Page: 75From: http://www.kumc.edu/instruction/medicine/anatomy/histoweb/cytology/large/Cyt001.JPG

04/18/23 Page: 76http://virtual.yosemite.cc.ca.us/randerson/Lynn's%20Bioslides/45.jpg

04/18/23 Page: 77http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/Bio%20101/Bio%20101%20Laboratory/Mitosis/Photographs/whitefish_mitosis_prophase_metaphase_anaphaseX400.jpg

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http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/Bio%20101/Bio%20101%20Laboratory/

Mitosis/Photographs/whitefish_mitosis_anaphaseX400.jpg

http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/Bio%20101/Bio%20101%20Laboratory/Mitosis/Photographs/whitefish_mitosis_telophaseX400.jpg

QuizQuiz Next time!Next time!

Regulating Cell Division (Cell Regulating Cell Division (Cell Cycle)Cycle)

Cells stop growing when they come in contact with each other-such as when a wound is healing

Cyclins-proteins within the cell that regulate the timing of eukaryotic cell division

a. Internal Cyclins-usually controls cell division events inside the cell like the beginning and end of cell cycle stages.

b. External Cyclins -for events outside the cell. These usually speed up or slow down the cell cycle and heal wounds.

Benign Tumor-a tumor that only grows in one place. Noninvasive and usually treatable

Malignant Tumor-invasive uncontrolled growth of cells

Skin Cancer

CANCERCANCEROccurs when cells do not respond to normal signals that regulate growth

*Most cancer cells have defect in the p53 gene

Make a little bookMake a little book

Page one – TitlePage two – interphase including G1, S, G2Page three – prophasePage four – metaphasePage five – anaphasePage six – telephasePage seven – cytokinesisPage eight – the end

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Test informationTest information Cell Cycle

– Order– S phase– Cancer– Interphase

Mitosis completed– What does each cell have?

Chromosomes Mitosis

– Prophase– Metaphase– Anaphase– Telophase

Cytokinesis