BiologyBiologyCh. 10Ch. 10Cell Growth and DivisionCell Growth and Division

Core Content: SC-HS-3.4.3Core Content: SC-HS-3.4.3

10–110–1 Cell GrowthCell Growth

A.A. Limits to Cell GrowthLimits to Cell Growth

1.1. DNA “Overload”DNA “Overload”

2.2. Exchanging MaterialsExchanging Materials

3.3. Ratio of Surface Area to Ratio of Surface Area to Volume Volume

4.4. Cell DivisionCell Division

Limits to Cell GrowthLimits to Cell Growth

The larger a cell becomes, the The larger a cell becomes, the more demands the cell places on more demands the cell places on its DNA.its DNA.

The cell has “DNA overload”, and The cell has “DNA overload”, and the needs of the growing cell can the needs of the growing cell can no longer be met.no longer be met.

The more trouble a cell has The more trouble a cell has moving enough nutrients and moving enough nutrients and wastes across the cell membrane.wastes across the cell membrane.

Surface area to Volume Surface area to Volume RatioRatio

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

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

Cell Size

Surface Area (length x width x 6)

Ratio of Surface Area Ratio of Surface Area to Volume in Cellsto Volume in Cells

Cell Size

Surface Area(l x w x 6)Volume(l x w x h)

Surface area toVolume ratio

10–210–2 Cell DivisionCell Division

A.A. ChromosomesChromosomesB.B. The Cell CycleThe Cell CycleC.C. Events of the Cell CycleEvents of the Cell CycleD.D. MitosisMitosis

1.1. ProphaseProphase2.2. MetaphaseMetaphase3.3. AnaphaseAnaphase4.4. TelophaseTelophase

E.E. CytokinesisCytokinesis

Cell DivisionCell Division

Before it becomes too large, a growing Before it becomes too large, a growing cell must divide into two “daughter” cell must divide into two “daughter” cells. This is cells. This is cell divisioncell division..

Before cell division occurs, the cell Before cell division occurs, the cell copies its DNA. This ensures that each copies its DNA. This ensures that each daughter cell gets a complete set of daughter cell gets a complete set of genetic information.genetic information.

Division increases the cell’s surface Division increases the cell’s surface area to volume ratio.area to volume ratio.

ChromosomesChromosomes Chromosomes are made of DNA, which Chromosomes are made of DNA, which

carries the cell’s coded genetic carries the cell’s coded genetic information, and proteins.information, and proteins.

Cells of each organisms have a specific Cells of each organisms have a specific number of chromosomes. Ex) humans number of chromosomes. Ex) humans have 46have 46

Chromosomes are not visible except Chromosomes are not visible except during cell division.during cell division.

Each chromosome consists of two Each chromosome consists of two identical “sister” identical “sister” chromatidschromatids that are that are attached at the attached at the centromerecentromere..

The Cell CycleThe Cell Cycle

During the cell cycle, a cell grows, During the cell cycle, a cell grows, prepares for division, and divides to prepares for division, and divides to form two new daughter cells.form two new daughter cells.

InterphaseInterphase is the period between is the period between divisions, and includes G1, S, and divisions, and includes G1, S, and G2 phases.G2 phases.

The M phase follows interphase, and The M phase follows interphase, and includes mitosis and cytokinesis.includes mitosis and cytokinesis.

includes

is divided into is divided into

Concept MapConcept MapSection 10-2

Cell Cycle

M phase (Mitosis)

Interphase

G1 phase S phase ProphaseG2 phase Metaphase TelophaseAnaphase

InterphaseInterphase

InterphaseInterphase takes much longer than takes much longer than actual cell division.actual cell division.

G1G1: Cells do most of their growing. : Cells do most of their growing. Cells increase in size and synthesize Cells increase in size and synthesize new proteins and organelles.new proteins and organelles.

SS: DNA is copied: DNA is copied G2G2: Cell prepares for mitosis, makes : Cell prepares for mitosis, makes

organelles and structures needed for organelles and structures needed for cell divisioncell division

M phase

G2 phase

S phase

G1 phase

Figure 10–4 The Cell CycleFigure 10–4 The Cell CycleSection 10-2

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MitosisMitosis

Following the events of Following the events of Interphase, the cell will begin to Interphase, the cell will begin to divide. This is divide. This is mitosismitosis..

Biologists divide mitosis into four Biologists divide mitosis into four phases: prophase, metaphase, phases: prophase, metaphase, anaphase, and telophaseanaphase, and telophase

ProphaseProphase

The first and longest phase of The first and longest phase of mitosis is prophase.mitosis is prophase.

During prophase, the chromatin During prophase, the chromatin condenses to form chromosomes.condenses to form chromosomes.

The centrioles separate, and a The centrioles separate, and a spindle begins to form.spindle begins to form.

The nuclear membrane breaks The nuclear membrane breaks down.down.

MetaphaseMetaphase

The stage following prophase is The stage following prophase is metaphase.metaphase.

During metaphase, the During metaphase, the chromosomes line up across the chromosomes line up across the center of the cell.center of the cell.

Each chromosome is connected Each chromosome is connected to a spindle fiber at its to a spindle fiber at its centromere.centromere.

AnaphaseAnaphase

Following metaphase is anaphase.Following metaphase is anaphase. During anaphase, the sister During anaphase, the sister

chromatids separate into individual chromatids separate into individual chromosomes and are moved chromosomes and are moved apart.apart.

The chromosomes form groups The chromosomes form groups near the poles of the spindle.near the poles of the spindle.

Anaphase ends when the Anaphase ends when the chromosomes stop moving.chromosomes stop moving.

TelophaseTelophase

The fourth and final stage of The fourth and final stage of mitosis is telophase.mitosis is telophase.

The chromosomes gather at The chromosomes gather at opposite ends of the cell, and lose opposite ends of the cell, and lose their distinct shapes.their distinct shapes.

Two nuclear membranes begin to Two nuclear membranes begin to form.form.

CytokinesisCytokinesis

Cell division is not complete until Cell division is not complete until cytokinesis occurs. Cytokinesis is cytokinesis occurs. Cytokinesis is division of the cytoplasm.division of the cytoplasm.

In animal cells, the cell membrane is In animal cells, the cell membrane is drawn inward until the cytoplasm is drawn inward until the cytoplasm is pinched into two equal parts.pinched into two equal parts.

In plants, a cell plate forms midway In plants, a cell plate forms midway between the divided nuclei. The cell between the divided nuclei. The cell plate gradually develops into a plate gradually develops into a separating membrane.separating membrane.

Cleavage furrow in Cleavage furrow in animal cellsanimal cells

Cell plate forming in Cell plate forming in plant cellplant cell

9–39–3 Regulating the Cell CycleRegulating the Cell Cycle

A.A. Controls on Cell DivisionControls on Cell Division

B.B. Cell Cycle RegulatorsCell Cycle Regulators

1.1. Internal RegulatorsInternal Regulators

2.2. External RegulatorsExternal Regulators

C.C. Uncontrolled Cell GrowthUncontrolled Cell Growth

Cell Cycle RegulatorsCell Cycle Regulators

Cyclins regulate the timing of the cell Cyclins regulate the timing of the cell cycle in eukaryotic cells.cycle in eukaryotic cells.

Proteins that respond to events inside Proteins that respond to events inside the cell are called the cell are called internal internal regulators.regulators.

Proteins that respond to events Proteins that respond to events outside the cell are called outside the cell are called external external regulators.regulators.

Most cells grow until they come in Most cells grow until they come in contact with other cells, then they stop contact with other cells, then they stop (contact inhibition).(contact inhibition).

Control of Cell Control of Cell DivisionDivision

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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.

Figure 10–8 Effect of CyclinsFigure 10–8 Effect of CyclinsSection 10-3

Uncontrolled cell Uncontrolled cell growthgrowth Cancer cells do not respond to the Cancer cells do not respond to the

signals that regulate the growth of most signals that regulate the growth of most cells.cells.

A defect in a gene called p53 has been A defect in a gene called p53 has been found in many types of cancer cells. found in many types of cancer cells.

They continue to grow out of control, and They continue to grow out of control, and can form masses of cells called can form masses of cells called tumorstumors..

Tumors can damage surrounding tissues.Tumors can damage surrounding tissues.

Benign vs. Malignant tumorsBenign vs. Malignant tumors

If the abnormal cells remain at If the abnormal cells remain at the original site, the tumor is the original site, the tumor is BENIGN and can usually be BENIGN and can usually be surgically removed.surgically removed.

If the tumor invades other If the tumor invades other organs and impairs their organs and impairs their function, the tumor is function, the tumor is MALIGNANT.MALIGNANT.

The spreading of cancer cells is The spreading of cancer cells is METASTASIS.METASTASIS.

BREAST CANCER

BREAST CANCER CELL

NORMAL MAMMOGRAM

CANCEROUSMASS

ApoptosisApoptosis– Programmed cell death.Programmed cell death.– Usually shrink and shrivel in a Usually shrink and shrivel in a

controlled process.controlled process.– Example: development of hands and Example: development of hands and

feet. Your hands and feet have feet. Your hands and feet have webbing between them in utero. webbing between them in utero. But when a baby is born this But when a baby is born this webbing is gone because of webbing is gone because of apoptosis.apoptosis.

– Example: leaves falling off trees and Example: leaves falling off trees and plants in autumn.plants in autumn.

Stem CellsStem Cells– Unspecialized cells that can develop Unspecialized cells that can develop

into specialized cells when under the into specialized cells when under the right conditions.right conditions.

– Two types: Embryonic and adult Two types: Embryonic and adult stem cells.stem cells. Embryonic—after fertilization the Embryonic—after fertilization the

resulting mass of cells divides rapidly resulting mass of cells divides rapidly until there are about 100-150 cells. until there are about 100-150 cells. These are cells that have not become These are cells that have not become specialized yet and can be used to specialized yet and can be used to repair damaged cells in others but is repair damaged cells in others but is highly controversial.highly controversial.

Adult stem cells—found in various Adult stem cells—found in various tissues in the body and might be tissues in the body and might be used to maintain and repair the used to maintain and repair the SAME kind of tissue in which they SAME kind of tissue in which they are found.are found.