Chapter 10Chapter 10Cell Growth & DivisionCell Growth & Division

Section 10-1Section 10-1

Cell GrowthCell Growth Read 1Read 1stst Paragraph Paragraph

Fig. 10-1Fig. 10-1

Limits To Cell GrowthLimits To Cell Growth 22 reasons why cells divide rather reasons why cells divide rather

than get larger.than get larger.1.1. They don’t have enough DNA.They don’t have enough DNA.2.2. They can’t move enough nutrients & They can’t move enough nutrients &

wastes across the cell membrane.wastes across the cell membrane.

DNA “Overload”DNA “Overload” Remember:Remember:

• DNA control’s cell function.DNA control’s cell function.• DNA is stored in the nucleus.DNA is stored in the nucleus.

When a cell is small, the info in DNA When a cell is small, the info in DNA is able to meet the cell’s needs.is able to meet the cell’s needs.• But, as a cell increases in size, But, as a cell increases in size, it doesn’t it doesn’t

make more DNAmake more DNA.. If it were to keep growing, there If it were to keep growing, there

would be an would be an “I“Information Crisisnformation Crisis””..

Cellular Cellular DNADNA

Compare the DNA in the nucleus to Compare the DNA in the nucleus to that of a small library.that of a small library.• Read P. 241Read P. 241

Middle paragraphMiddle paragraph

Exchanging MaterialsExchanging Materials

Recall that Recall that foodfood, , HH22OO, & , & OO22 pass pass through CM’s easily by through CM’s easily by passivepassive & & activeactive transport. transport.

WasteWaste also leaves the cell through also leaves the cell through the cell membrane.the cell membrane.

The rate at which these exchanges take place The rate at which these exchanges take place depends on the surface area of the cell.depends on the surface area of the cell.• Surface areaSurface area =Total area of the cell membrane =Total area of the cell membrane

(CM).(CM).

However, the rate at which However, the rate at which foodfood & & OO22 are are taken in, & taken in, & wasteswastes produced depends on the produced depends on the cell’s volume.cell’s volume.

• VolumeVolume =How much space is in the cell. =How much space is in the cell.

Surface Area –Volume RatioSurface Area –Volume Ratio Imagine a cell shaped like a cube.Imagine a cell shaped like a cube.

• p. 243, fig. 10-2p. 243, fig. 10-2 Follow along! Follow along!

Important things to note:Important things to note:• Volume increases much Volume increases much fasterfaster than surface than surface

area.area. This causes the surface area-volume ratio to This causes the surface area-volume ratio to

decrease.decrease. This causes serious problems for the cell.This causes serious problems for the cell.

http://plaza.ufl.edu/alallen/pgl/modules/rio/stingarees/module/why.html

Surface Area to Volume RatioSurface Area to Volume Ratio

Cell Size

Surface Area (length x width x 6)

Volume (length x width x height)

Ratio of Surface Area to Volume

Use the Use the street –trafficstreet –traffic analogy. analogy.• Read Read p. 242p. 242, bottom paragraph., bottom paragraph.

If a cell got If a cell got too bigtoo big, it would have , it would have trouble getting enough trouble getting enough OO22 & & nutrientsnutrients in, & in, & waste waste out.out.

Division of the CellDivision of the Cell Before cells get too big they divide.Before cells get too big they divide.

• Division creates Division creates 22 “ “daughter cellsdaughter cells”.”. This is called This is called cell divisioncell division..

Before cell division occurs, the cell Before cell division occurs, the cell copies its DNA.copies its DNA.• This solves the problem of info This solves the problem of info

shortages.shortages. Cell division also solves the volume Cell division also solves the volume

problem.problem.• By reducing size, the cell reduces By reducing size, the cell reduces

volume.volume.

Cell DivisionCell Division

Read Read p. 244p. 244 top paragraph top paragraph In In prokaryotes prokaryotes (pro-k)(pro-k), cell division is , cell division is

just the splitting of the cell into just the splitting of the cell into 22 parts. parts. In In eukaryoteseukaryotes (eu-k)(eu-k), cell division is , cell division is

complex & happens in complex & happens in 22 stages: stages:• MitosisMitosis• CytokinesisCytokinesis

Section 10-2Section 10-2Cell DivisionCell Division

Prokaryotic Cell DivisionProkaryotic Cell Division

Reproduction through mitosis Reproduction through mitosis is considered is considered asexualasexual..All the cells are identical to the parent cell.What are the resulting cells called?

ChromosomesChromosomes In eukaryotes, genetic info is carried by In eukaryotes, genetic info is carried by

chromosomes.chromosomes. Chromosomes are made of Chromosomes are made of DNA & proteinsDNA & proteins..

Every org. has a certain # of chromosomes:Every org. has a certain # of chromosomes: Examples:Examples:

• Fruit flies =Fruit flies = 88• Carrot cells = 18Carrot cells = 18• Human cells = 46Human cells = 46• Dog = 78Dog = 78• Sweet potato = 90Sweet potato = 90

Chromosomes are normally visible Chromosomes are normally visible onlyonly during cell division. during cell division.• The rest of the time they are in a form The rest of the time they are in a form

known as known as chromatinchromatin..Before cell division happens, chromosomes are copied.For this reason, each chromosome consists of TWOTWO identical “sister” “sister” chromatids. See p. 244, Fig. 10-3See p. 244, Fig. 10-3

When cells divide, the When cells divide, the ““sistersister” chromatids separate ” chromatids separate from each other.from each other.• 11 chromatid goes to each of chromatid goes to each of

the the 22 new cells. new cells.

Chromatids are held together by a Chromatids are held together by a centromerecentromere..• Normally located @ the middle of the chromatidNormally located @ the middle of the chromatid

Some can lie near the ends.Some can lie near the ends. A human cell contains 46 chromosomes A human cell contains 46 chromosomes

(sometimes referred to as 23 pairs)(sometimes referred to as 23 pairs)• Each consisting of 2 chromatids.Each consisting of 2 chromatids.

The Cell CycleThe Cell Cycle

Cell cycleCell cycle –series of events that cells –series of events that cells go through as they grow & divide.go through as they grow & divide.

InterphaseInterphase –period b/t cell divisions. –period b/t cell divisions.During each cell cycle:

A cell growsPrepares for divisionDivides to form 22 daughter cellsp. 245, fig. 10-4p. 245, fig. 10-4

TheTheCell Cell

CycleCycle

G1

S

G2

Consists of 4 phases:

G1 PhaseS PhaseG2 PhaseM Phase

Events of the Cell CycleEvents of the Cell Cycle Most of a cell’s life is spent in Most of a cell’s life is spent in interphaseinterphase.. Interphase is divided into Interphase is divided into 33 phases: phases:

• G1G1 Cells do most of their growing.Cells do most of their growing. New proteins & organelles are also made.New proteins & organelles are also made.

• SS Chromosomes are copied.Chromosomes are copied. Synthesis of DNA molecules takes place.Synthesis of DNA molecules takes place.

• G2G2 Shortest of the 3 phases.Shortest of the 3 phases. Organelles & molecules required for cell division are Organelles & molecules required for cell division are

made.made.

When the G2G2 phase is done, the cell is ready to enter the M phase. a.k.a. = cell division

MitosisMitosis Divided into Divided into 44 phases: phases:

• ProphaseProphase• MetaphaseMetaphase• AnaphaseAnaphase• TelophaseTelophase

Depending on the cell, mitosis can Depending on the cell, mitosis can last from minutes to days.last from minutes to days.

PMATPMAT

ProphaseProphase 11stst & longest phase. & longest phase. Chromosomes become visible.Chromosomes become visible. Centrioles separate & take up positions on Centrioles separate & take up positions on

opposite sides of the nucleus.opposite sides of the nucleus.CentriolesCentrioles -2 tiny structures located near the nuclear -2 tiny structures located near the nuclear

envelope.envelope.

SpindleSpindle –a fanlike –a fanlike Microtubule structure that Microtubule structure that helps helps

separateseparate chromosomeschromosomes..• Plant cells Plant cells don’tdon’t have centrioles. have centrioles.

Near the end of prophase:Near the end of prophase:Chromosomes coil more Chromosomes coil more tightly. tightly.The nucleolus disappears.The nucleolus disappears.The nuclear envelope The nuclear envelope breaks down.breaks down.

MetaphaseMetaphase 22ndnd phase phase

Often lasts only a few Often lasts only a few minutes.minutes.

Chromosomes line up at the midline or Chromosomes line up at the midline or equator of the cell.equator of the cell.

The centromeres of each chromosome The centromeres of each chromosome connect to the spindle.connect to the spindle.

AnaphaseAnaphase

33rdrd phase phase

During anaphase:During anaphase:• The centromeres joining the sister chromatids, The centromeres joining the sister chromatids,

separate & become individual chromosomes.separate & become individual chromosomes.• These chromosomes then move to opposite ends These chromosomes then move to opposite ends

of the cell called of the cell called polespoles..• Anaphase ends when the chromosomes stop Anaphase ends when the chromosomes stop

moving.moving.

TelophaseTelophase The The 4th4th & final phase. & final phase. Chromosomes begin to disperse into a tangle of Chromosomes begin to disperse into a tangle of

dense material.dense material. The nuclear envelope The nuclear envelope reforms around the reforms around the chromosomes.chromosomes.

The spindle breaks apart.The spindle breaks apart. The nucleolus becomesThe nucleolus becomes visible again.visible again.

includes

is divided into is divided into

Cell Cycle

M phase (Mitosis)

Interphase

G1 phase S phase ProphaseG2 phase Metaphase TelophaseAnaphase

Interphase

Prophase

Metaphase

Anaphase

Telophase

CytokinesisCytokinesis CytokinesisCytokinesis –the division of the –the division of the

cytoplasm.cytoplasm.• Cytokinesis usually occurs at the same Cytokinesis usually occurs at the same

time as telophase.time as telophase. It occurs in primarily It occurs in primarily 22 ways: ways:

• By pinching off b/t the 2 daughter cells By pinching off b/t the 2 daughter cells equally.equally.

Done in animal cells.Done in animal cells.• By building a cell plate b/t the 2 cells.By building a cell plate b/t the 2 cells.

Done in plant cells.Done in plant cells.

Mitosis VideoMitosis Video http://www.johnkyrk.com/mitosis.htm

l

https://www.youtube.com/watch?https://www.youtube.com/watch?v=TlYqh5OfJFkv=TlYqh5OfJFk

Section 10-3Section 10-3

Regulating the Cell CycleRegulating the Cell Cycle

Note!Note!• Not all cells move through the cell cycle Not all cells move through the cell cycle

at same rate.at same rate. Ex:Ex:

• Muscle cells & nerve cells don’t divide at Muscle cells & nerve cells don’t divide at all, once they are developed.all, once they are developed.

• Skin cells, digestive cells, & cells in bone Skin cells, digestive cells, & cells in bone marrow that make blood cells, divide marrow that make blood cells, divide rapidly throughout our life.rapidly throughout our life.

• Rapidly dividing cells can pass through a Rapidly dividing cells can pass through a cell cycle every few hrs.cell cycle every few hrs.

Controls of Cell DivisionControls of Cell Divisionfig.10-7fig.10-7

This illustration shows that cell This illustration shows that cell division can be turned on & off.division can be turned on & off.

The same thing happens when we The same thing happens when we have a cut in the skin or a broken have a cut in the skin or a broken bone.bone.• New cells are made until the wound is New cells are made until the wound is

healed, then they stop dividing.healed, then they stop dividing.

Fig. 10-7Fig. 10-7

Cells in a petri dish will continue to Cells in a petri dish will continue to grow until they come into contact w/ grow until they come into contact w/ other cells.other cells.

Cell Cycle RegulatorsCell Cycle Regulators

In the 1980’s, scientists discovered In the 1980’s, scientists discovered what controls the cell cycle.what controls the cell cycle.• The substance was a protein called The substance was a protein called cyclincyclin..• Cyclin regulates the cell cycle.Cyclin regulates the cell cycle.

Since this discovery, scientists have Since this discovery, scientists have found other proteins that are involved found other proteins that are involved in the cell cycle.in the cell cycle.• They call all these proteins They call all these proteins cyclinscyclins..

p. 251, fig. 10-8p. 251, fig. 10-8

Fig. 10-8Fig. 10-8

A sample of cytoplasm is removed from a cell in mitosis.

The sample is injected into a second cell in G2 of interphase.

As a result, the second cell enters mitosis.

There are There are 22 types of regulatory types of regulatory proteins:proteins:

• Internal RegulatorsInternal Regulators• External RegulatorsExternal Regulators

Internal RegulatorsInternal Regulators Made up of proteins that respond to Made up of proteins that respond to

events events insideinside the cell. the cell. Allows the cell to only proceed when Allows the cell to only proceed when

certain events have happened.certain events have happened. Ex:Ex:

• Cells wont move to the next phase in Cells wont move to the next phase in mitosis until all the right steps have mitosis until all the right steps have been completed.been completed.

External RegulatorsExternal Regulators Made up of proteins that respond to Made up of proteins that respond to

events events outsideoutside the cell. the cell. They direct cells to speed up or slow They direct cells to speed up or slow

down the cell cycle.down the cell cycle. Important during wound healing & Important during wound healing &

embryonic development.embryonic development.

Uncontrolled Cell DivisionUncontrolled Cell Division CancerCancer –a disorder in which some of the –a disorder in which some of the

body's own cells lose the ability to body's own cells lose the ability to control growth.control growth.

Cancer cells don’t respond to the Cancer cells don’t respond to the signals that regulate the growth of most signals that regulate the growth of most cells.cells.• As a result they divide uncontrollably & As a result they divide uncontrollably &

form masses of cells called form masses of cells called tumorstumors.. Tumors can damage surrounding tissues.Tumors can damage surrounding tissues.

• Cancer cells can also move throughout the Cancer cells can also move throughout the body & cause serious problems, or even body & cause serious problems, or even death.death.

What can cause cancer?What can cause cancer?• TobaccoTobacco

Smokeless or smokedSmokeless or smoked• RadiationRadiation

X-rayX-ray UVUV RadioactiveRadioactive

• Viral infectionsViral infections HPV-cervical cancer HPV-cervical cancer (inoculation available)(inoculation available)

Another cause is a damaged gene in a Another cause is a damaged gene in a chromosome called the chromosome called the p53p53 gene. gene.• Damage to the Damage to the p53p53 gene causes the cell to gene causes the cell to

lose the info needed to respond to signals lose the info needed to respond to signals that would normally control their growth.that would normally control their growth.

Cell Cycle GameCell Cycle Game http://www.pinterest.com/pin/245375

879673392966/

http://www.pinterest.com/pin/245375879673389251/

http://nobelprize.org/educational_games/medicine/2001/cellcycle.html

Stem CellsStem Cells