Cell Growth and Cell Growth and ReproductionReproduction

Chapter 5Chapter 5

Limits to Cell SizeLimits to Cell Size Cell is Cell is too smalltoo small::

Not enough roomNot enough room for organelles and for organelles and moleculesmolecules

As a cell grows, its volume increases much As a cell grows, its volume increases much faster than its surface area.faster than its surface area.

Cell is Cell is too bigtoo big:: DiffusionDiffusion of molecules will be of molecules will be too slowtoo slow..

Why can’t most organisms be just one Why can’t most organisms be just one giant cell?giant cell?

DiffusionDiffusion limits cell size limits cell size DNADNA limits cell size limits cell size Surface area-to-volume ratioSurface area-to-volume ratio

As cell’s size increases, its volume As cell’s size increases, its volume increases much faster than its surface increases much faster than its surface areaarea

Cell ReproductionCell ReproductionChromosomes:Chromosomes: 1.1. Structures that contain DNAStructures that contain DNA2.2. Dark when stained.Dark when stained.3.3. Carriers of genetic material (Carriers of genetic material (passed passed

from generation to generationfrom generation to generation.).)4.4. Typically exist as Typically exist as chromatinchromatin – ( – (long long

strands of DNA wrapped around strands of DNA wrapped around proteinsproteins.).)

The Cell CycleThe Cell Cycle Occurs in Eukaryotic CellsOccurs in Eukaryotic Cells Regular pattern of: Regular pattern of:

GrowthGrowth DNA duplication DNA duplication cell division cell division

4 Stages in the cell cycle:4 Stages in the cell cycle:

Gap 1 (GGap 1 (G11), Synthesis, Gap 2 (G), Synthesis, Gap 2 (G22), Mitosis), Mitosis Enzymes control the transfer through the Enzymes control the transfer through the

stagesstages

Gap 1 (GGap 1 (G11))

First StageFirst Stage Cell carries out normal functionsCell carries out normal functions Cell increases in sizeCell increases in size Organelles increase in numberOrganelles increase in number

SynthesisSynthesis

Second StageSecond Stage Synthesis = “the combining of parts to Synthesis = “the combining of parts to

make a whole”make a whole” Cell makes a copy of its DNACell makes a copy of its DNA

Gap 2 (GGap 2 (G22))

Third StageThird Stage Similar to GSimilar to G11 phase phase Includes a critical checkpoint … the cell Includes a critical checkpoint … the cell

will only reproduce if everything is in will only reproduce if everything is in order.order.

The Cell CycleThe Cell Cycle The sequence of The sequence of GROWTHGROWTH and and

DIVISIONDIVISION of a cell: of a cell: InterphaseInterphase – Growth stage of cell cycle – Growth stage of cell cycle MitosisMitosis – Division stage of cell cycle. – Division stage of cell cycle.

ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophase

CytokinesisCytokinesis – process in which cell’s – process in which cell’s cytoplasm dividescytoplasm divides

InterphaseInterphase

1.1. Precedes MitosisPrecedes Mitosis

2.2. Includes G1, Synthesis, and G2 stagesIncludes G1, Synthesis, and G2 stages

3.3. Most of a cell’s life is spent in this Most of a cell’s life is spent in this growth stagegrowth stage

4.4. Chromosomes are duplicated in Chromosomes are duplicated in preparation for cell divisionpreparation for cell division

ProphaseProphase1.1. First and First and longest stage of Mitosislongest stage of Mitosis

2.2. Chromatin uncoilsChromatin uncoils to form visible chromosomes to form visible chromosomes

3.3. Chromosomes composed of two halves called Chromosomes composed of two halves called sister chromatidssister chromatids

4.4. Sister chromatids are held together by a Sister chromatids are held together by a centromerecentromere..

5.5. Nuclear Envelope disintegratesNuclear Envelope disintegrates (disappears) (disappears)

6.6. Centrioles and spindles help in chromatid Centrioles and spindles help in chromatid separationseparation

PROPHASEPROPHASE

MetaphaseMetaphase

1.1. 22ndnd phase of mitosis phase of mitosis

2.2. Chromosomes move to the equatorChromosomes move to the equator

3.3. Each Each sister chromatidsister chromatid is attached to its is attached to its own spindle fiberown spindle fiber

4.4. Spindle fibers are Spindle fibers are attached to centromereattached to centromere

METAPHASEMETAPHASE

AnaphaseAnaphase

1.1. 33rdrd phase of mitosis phase of mitosis

2.2. CentromeresCentromeres are are splitsplit

3.3. Sister Chromatids are pulled apartSister Chromatids are pulled apart

ANAPHASEANAPHASE

TelophaseTelophase

1.1. 44thth and and Final stage of MitosisFinal stage of Mitosis

2.2. Chromatids reach opposite polesChromatids reach opposite poles of the cell of the cell

3.3. Two distinct daughter cells are formedTwo distinct daughter cells are formed

4.4. Processes of prophase are reversedProcesses of prophase are reversed

TELOPHASETELOPHASE

Results of MitosisResults of Mitosis Creates Creates two new cellstwo new cells from original from original::

Chromosome sets are identical to parent Chromosome sets are identical to parent cell.cell.

Guarantees genetic continuityGuarantees genetic continuity Creates tissues, organs, and organ Creates tissues, organs, and organ

systemssystems

Interphase

Metaphase Anaphase

Telephase/

Daughter Cells

Prophase

Mitosis of an onion cell

Mitosis of a White Fish Blastula Cell

What is CancerWhat is Cancer

22ndnd leading cause of death in U.S. leading cause of death in U.S. ½ of men and 1/3 of women develop it½ of men and 1/3 of women develop it 200 different types200 different types Risk can be reduced by lifestyle changesRisk can be reduced by lifestyle changes

Normal Cell OrganizationNormal Cell Organization

Groups of cells form organs which Groups of cells form organs which produce functions.produce functions.

Early in life, cells divide frequentlyEarly in life, cells divide frequently Later in life, cells only grow and divide to Later in life, cells only grow and divide to

replace old cells or repair injuriesreplace old cells or repair injuries

Cancer Cell OrganizationCancer Cell Organization

Abnormal Cells Abnormal Cells (mutated DNA or don’t (mutated DNA or don’t perform proper function)perform proper function) Inherit damaged DNA from ParentsInherit damaged DNA from Parents Damaged by exposure to something Damaged by exposure to something

(sunlight, smoking, etc.)(sunlight, smoking, etc.) Out of control cell multiplication; forms Out of control cell multiplication; forms

mass of cells (tumors)mass of cells (tumors)