Ch 10: Cell Growth and Ch 10: Cell Growth and DivisionDivision

CellsCells

Do not continue Do not continue to grow bigger, to grow bigger, instead they instead they produce more cellsproduce more cells

Why is this?Why is this?

1. The larger a cell becomes, the 1. The larger a cell becomes, the more demands the cell places on its more demands the cell places on its DNA (genetic material).DNA (genetic material).

2. The cell has more trouble 2. The cell has more trouble moving enough nutrients and moving enough nutrients and wastes across the cell membrane.wastes across the cell membrane.

Cell DivisionCell Division

growth and repair growth and repair in eukaryotesin eukaryotes

one one parentparent cell cell divides into 2 new divides into 2 new daughterdaughter cellscells

Cell DivisionCell Division

The parent cell passes The parent cell passes on an exact copy of on an exact copy of their chromosomes their chromosomes (located in DNA) to (located in DNA) to their daughter cells!their daughter cells!

What is the cell cycle?What is the cell cycle?

Continuous process Continuous process where cells grow, where cells grow, make copies of their make copies of their chromosomes, and chromosomes, and divide to form divide to form daughter cells.daughter cells.

Cell Cycle has 3 Cell Cycle has 3 Phases:Phases:

1.1. InterphaseInterphase

2.2. MitosisMitosis

3.3. CytokinesisCytokinesis

The cell cycleThe cell cycle

1 hour – several days 1 hour – several days depending on the type depending on the type of cell involved.of cell involved.

Cell CycleCell Cycle

InterphaseInterphaseWhere most time is Where most time is spent. Growth and spent. Growth and DNA replication DNA replication (copying) occur(copying) occur

InterphaseInterphase

3 stages3 stages G1G1 S phaseS phase G2G2

G1 PhaseG1 Phase

Cell growsCell grows

synthesize synthesize new proteins new proteins and organellesand organelles

New New cytoplasm cytoplasm formsforms

S PhaseS Phase

ChromosoChromosomes mes duplicateduplicate

G2 PhaseG2 Phase

Growth Growth continuescontinues

Prepare Prepare for mitosisfor mitosis

MitosisMitosis

Makes up most of the “M Makes up most of the “M Phase.”Phase.”

Nucleus divides into new Nucleus divides into new nucleinuclei

Each nucleus has a complete Each nucleus has a complete set of chromosomes.set of chromosomes.

MitosisMitosis

4 Phases (PMAT):4 Phases (PMAT): ProphaseProphase

MetaphaseMetaphase

AnaphaseAnaphase

TelophaseTelophase

ProphaseProphaseChromosomes becomes visibleChromosomes becomes visible

Sister chromatids are attached at the Sister chromatids are attached at the centromere.centromere.

Nuclear membrane breaks downNuclear membrane breaks down

Centrioles travel to opposite poles of Centrioles travel to opposite poles of the cell.the cell.

A fanlike spindle forms around each A fanlike spindle forms around each centriole.centriole.

Chromosomes Chromosomes within Prophasewithin Prophase

carry genetic carry genetic informationinformation

consists of DNAconsists of DNA cells have a specific cells have a specific number of number of chromosomeschromosomes

Chromosomes Chromosomes continued…continued…

Humans have 46 chromosomes in each cell

ChromatidsChromatids

Paired strands of a Paired strands of a duplicated duplicated chromosome.chromosome.

Attached at a Attached at a centrral region called centrral region called the the centromerecentromere

Centromere

Chromatid

MetaphaseMetaphase

Chromatids line up Chromatids line up across the center of the across the center of the cellcell

Centromeres are Centromeres are attached to a spindle attached to a spindle fiber.fiber.

Metaphase Metaphase

AnaphaseAnaphase

Spindle fibers pull sister Spindle fibers pull sister chromatids apart at chromatids apart at centromeres to opposite ends centromeres to opposite ends of the cell. of the cell.

TelophaseTelophase Chromosomes reach opposite Chromosomes reach opposite

poles of the cell and begin to poles of the cell and begin to uncoil.uncoil.

Spindle breaks downSpindle breaks down

Nuclear membranes reform Nuclear membranes reform around the chromosomes at each around the chromosomes at each polepole

The cell has 2 identical nuclei The cell has 2 identical nuclei each with a complete set of each with a complete set of chromosomes.chromosomes.

CytokinesisCytokinesis

Division of cytoplasm Division of cytoplasm into 2 separate cellsinto 2 separate cells

Works different for animal Works different for animal and plant cells.and plant cells.

CytokinesisCytokinesisAnimal Cells = Central groove called a Animal Cells = Central groove called a

“cleavage furrow” forms in the plasma “cleavage furrow” forms in the plasma membrane and pinches the 2 daughter membrane and pinches the 2 daughter cells apart.cells apart.

Plant Cells= Involves the formation of Plant Cells= Involves the formation of a cell plate between the nuclei. Cell a cell plate between the nuclei. Cell plate then transforms part of the cell plate then transforms part of the cell wall of each new cell.wall of each new cell.

CytokinesisCytokinesis

This process is found in This process is found in unicellular eukaryotes and unicellular eukaryotes and

some multicellular organismssome multicellular organisms

Use cell division to make Use cell division to make NEWNEW cells cells

Organisms also use Organisms also use mitosis to mitosis to REPLACEREPLACE cells cells that are damaged or no that are damaged or no longer useful to the longer useful to the organism.organism.

For example……For example……

Your body continuously makes new Your body continuously makes new skin cells by mitosis to replace skin skin cells by mitosis to replace skin cells that are worn out.cells that are worn out.

Mitosis is….Mitosis is….

Asexual Reproduction Asexual Reproduction = = Production of offspring by a single parent.Production of offspring by a single parent.

Offspring are then exact copies of their Offspring are then exact copies of their parents.parents.

Examples: Yeasts and freshwater animals Examples: Yeasts and freshwater animals (Hydras) reproduce this way. Their (Hydras) reproduce this way. Their offspring develop from buds on the offspring develop from buds on the parents body.parents body.

Organisms that Organisms that reproduce asexuallyreproduce asexually

CyclinCyclin

proteinprotein regulates the regulates the timing of the cell timing of the cell cycle in cycle in eukaryotic cellseukaryotic cells

Regulatory Regulatory ProteinsProteins

Two typesTwo types1.1.Internal Internal

RegulatorsRegulators2.2.External External

RegulatorsRegulators

Internal RegulatorsInternal Regulators proteins that proteins that respond to events respond to events inside the cellinside the cell

signals cell cycle to signals cell cycle to continue ONLY WHEN continue ONLY WHEN OTHER THINGS ARE OTHER THINGS ARE COMPLETECOMPLETE

External RegulatorExternal Regulator

proteins that respond to proteins that respond to events outside the cellevents outside the cell

direct cells to speed up direct cells to speed up or slow down the cell or slow down the cell cyclecycle

example: growth example: growth regulatorsregulators

Why is cell Why is cell growth regulated growth regulated

so carefully?so carefully?

Uncontrolled Cell Uncontrolled Cell GrowthGrowth

CancerCancer body loses ability to body loses ability to control growthcontrol growth

does not respond to the does not respond to the regulator proteinsregulator proteins

result = large masses of result = large masses of cells cells

TumorsTumors

masses of cellsmasses of cells

damages the damages the surrounding tissuessurrounding tissues

cells break off and cells break off and spread throughout the spread throughout the body body

Cause of cancerCause of cancer brought on by brought on by smoking tobaccosmoking tobacco

radiation exposureradiation exposure viral infectionviral infection etcetc

All cancers have one All cancers have one thing in common….thing in common….

The cell cycle has broken The cell cycle has broken downdown