Cell Growth and DivisionCell Growth and Division

Cell SizeCell Size8 micrometers in diameter to 1 meter 8 micrometers in diameter to 1 meter

with small diameters.with small diameters.Most cells are between 2 and 200 Most cells are between 2 and 200

micrometers in diameter.micrometers in diameter.Human Body: Human Body:

– Smallest: sperm cellsSmallest: sperm cells– Largest: ovumLargest: ovum– Longest: nerve cellsLongest: nerve cells

Largest Living Cell- Ostrich Egg (unfertilized)Largest Living Cell- Ostrich Egg (unfertilized)

Comparison of Cell sizesComparison of Cell sizes

Cell Size LimitationsCell Size Limitations

Cell must be smallCell must be small– Large need more foodLarge need more food– Must export wasteMust export waste

Rate of DiffusionRate of Diffusion– Size :diffusion slower and less efficient.Size :diffusion slower and less efficient.

DNA (molecule where critical information DNA (molecule where critical information stored) Too large “Information Crisis”stored) Too large “Information Crisis”– Cell cannot survive unlessCell cannot survive unless

• enough DNA to support protein needsenough DNA to support protein needs• cell activities are carried out quickly and efficientlycell activities are carried out quickly and efficiently

Cell Size IncreaseCell Size Increase

Not enough cell membrane to adequately supply the cell interior with enough oxygen, water, and food.

Result: Cell Death

Surface area-to-volume ratioSurface area-to-volume ratio As cell’s size increases, its As cell’s size increases, its

volume increases much faster volume increases much faster than its surface area.than its surface area.

Surface Area and VolumeSurface Area and Volume

Surface Area: 6 (# of sides) x A x ASurface Area: 6 (# of sides) x A x AVolume: A x A X AVolume: A x A X A

•Cube doubledCube doubled•Outside Grows by 4 xOutside Grows by 4 x•Inside grows by 8 xInside grows by 8 x

Cell Growth and ReproductionCell Growth and Reproduction

Asexual Versus Sexual Asexual Versus Sexual ReproductionReproduction

AsexualAsexual Genetically identical Genetically identical

offspringoffspring Single Cell Single Cell

– ex. Bacteriaex. Bacteria Multi Cellular- Break off Multi Cellular- Break off

and new organism and new organism produced produced – ex. Hydraex. Hydra

SexualSexual Offspring inherit genetic Offspring inherit genetic

information from each information from each parent.parent.

Most plants and animals, Most plants and animals, some single celled some single celled organisms.organisms.

Asexual Versus Sexual Asexual Versus Sexual ReproductionReproduction

AsexualAsexual Survival StrategySurvival Strategy Better the conditions the Better the conditions the

faster reproduce, better faster reproduce, better chance of survival,chance of survival,

As long as conditions As long as conditions favorable; genetically favorable; genetically identical has advantagesidentical has advantages

Lack of diversity a Lack of diversity a disadvantage when disadvantage when conditions change and conditions change and are not favorable. are not favorable.

SexualSexual Different survival strategyDifferent survival strategy Finding a mate, growth Finding a mate, growth

and development take and development take more time.more time.

Genetic diversity; better Genetic diversity; better tolerate changetolerate change

Both Sexual and AsexualBoth Sexual and Asexual

Ex. YeastEx. YeastMostly asexual, however, may under certain Mostly asexual, however, may under certain

conditions reproduce sexually.conditions reproduce sexually.

Cell TheoryCell TheoryAll cells come from pre-existing All cells come from pre-existing

cells!cells!

Cell division results in two cells Cell division results in two cells that are identical to the original that are identical to the original

parent cell.parent cell.

Prokaryotic CellsProkaryotic Cells

Lack nucleus & many organellesLack nucleus & many organellesDNA molecule found in cytoplasmDNA molecule found in cytoplasmMost contain single, circular DNA with all Most contain single, circular DNA with all

genetic informationgenetic information

ChromosomesChromosomesChromaChroma (Greek) “colored” (Greek) “colored”

SomaSoma “body” “body”Genetic information is bundled into Genetic information is bundled into

packages of DNApackages of DNA

Structure of the Eukaryotic Structure of the Eukaryotic ChromosomeChromosome

Exist as CHROMATIN—Long strands of DNA Exist as CHROMATIN—Long strands of DNA wrapped around proteins.wrapped around proteins.

Microscope—Plate of spaghettiMicroscope—Plate of spaghetti

Components•Sugar-Deoxy-ribose –derived from ribose sugar-one less oxygen•Phosphate Group -backbone•4 Nitrogen Bases-In complementary base pairs held by hydrogen bonds

• Adenine & Thymine• Cytosine &Guanine

CHROMOSOMESCHROMOSOMES

Make it possible to separate DNA Make it possible to separate DNA precisely during cell divisionprecisely during cell division

CELL CYCLECELL CYCLE

• A series of events the cells go through A series of events the cells go through as they grow and divideas they grow and divide

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

Prokaryotic Cell CycleProkaryotic Cell Cycle

Regular pattern of Regular pattern of growth, DNA growth, DNA replication, and cell replication, and cell division that can take division that can take place under ideal place under ideal conditionsconditions

Just beginning to Just beginning to understand processunderstand process

Form of reproduction Form of reproduction called Binary Fission.called Binary Fission.

Result-two genetically Result-two genetically identical cells.identical cells.

Cell CycleCell Cycle

– InterphaseInterphase-Period of cell cycle b/w cell -Period of cell cycle b/w cell divisiondivision• most of the cell’s metabolic functions are most of the cell’s metabolic functions are

carried outcarried out• chromosomes are replicated chromosomes are replicated • LONGEST of Cell CycleLONGEST of Cell Cycle

– Cell Division (M Phase)Cell Division (M Phase)• MitosisMitosis when nuclear division occurs, leading when nuclear division occurs, leading

to the formation of two daughter cells.to the formation of two daughter cells.• The division of the cytoplasm, called The division of the cytoplasm, called

cytokinesiscytokinesis, follows mitosis., follows mitosis.

• Length of cell cycle depend on the type of cellLength of cell cycle depend on the type of cell

Eukaryotic Cell CycleEukaryotic Cell Cycle

Interphase: Cell prepares for Interphase: Cell prepares for MitosisMitosis

Cell grows in sizeCell grows in sizeCarry on metabolismCarry on metabolismChromosomes are duplicated for cell Chromosomes are duplicated for cell

division.division.

InterphaseInterphase

G1 Phase: Cell Growth

• Most cell growth

• Increase in size

• Synthesize new proteins and organelles

Interphase ContinuedInterphase Continued

S PhaseS Phase

““S” SynthesisS” Synthesis DNA is synthesized when DNA is synthesized when

chromosomes replicated.chromosomes replicated. Result: Cell has 2x as Result: Cell has 2x as

much DNAmuch DNA

GG22 Phase: Preparing for Cell Phase: Preparing for Cell DivisionDivision

Shortest phase of Shortest phase of InterphaseInterphase

Organelles and Organelles and molecules required for molecules required for cell division are cell division are produced.produced.

Result: Cell ready for Result: Cell ready for divisiondivision

Nitrogen Bases

Helicase-(Enzyme) unzips/breaks hydrogen bonds b/w base pairs

M PhaseM Phase

Produces 2 daughter cellsProduces 2 daughter cells““M” comes from MitosisM” comes from MitosisCell division relatively quickCell division relatively quick Includes Mitosis and CytokinesisIncludes Mitosis and Cytokinesis

– Mitosis-division of the cell nucleusMitosis-division of the cell nucleus• 2 daughter cells produced with genetic information2 daughter cells produced with genetic information

– Cytokinesis-division of the cytoplasmCytokinesis-division of the cytoplasm

Mitosis: A period of nuclear Mitosis: A period of nuclear divisiondivision

MitosisMitosis

ProphaseProphaseMetaphaseMetaphaseAnaphaseAnaphaseTelophaseTelophase

ProphaseProphase11stst / longest phase of mitosis. / longest phase of mitosis. Chromatin coils up (condenses)-Chromatin coils up (condenses)-

chromosomes.chromosomes.Duplicate chromosomes become visibleDuplicate chromosomes become visibleTwo halves of the double structure are called Two halves of the double structure are called

sister chromatids. sister chromatids. (Exact Copies of each (Exact Copies of each other)other)

CentromereCentromere—holds together sister —holds together sister chromatids.chromatids.

Prophase continued…Prophase continued…

Nucleus disappears Nucleus disappears Nuclear envelope and nucleolus disintegrate.Nuclear envelope and nucleolus disintegrate.Animals—centrioles migrate to opposite end Animals—centrioles migrate to opposite end

of the cell.of the cell.CentrioleCentriole—Small, dark, cylindrical structures —Small, dark, cylindrical structures

that are made of microtubules and are that are made of microtubules and are located just outside the nucleus.(animal cells located just outside the nucleus.(animal cells only)only)

Prophase continued…Prophase continued…

SpindleSpindle—A football shaped, cage-like —A football shaped, cage-like structure consisting of thin fibers made of structure consisting of thin fibers made of microtubules.microtubules.

Metaphase: Second stage of Metaphase: Second stage of mitosismitosis

Chromosomes Chromosomes – Line up at center of cellLine up at center of cell– Attach to the spindle fibers via centromeres.Attach to the spindle fibers via centromeres.– Pulled by spindle fibers and line up on the midline Pulled by spindle fibers and line up on the midline

(equator).(equator). One sister chromatid’s spindle fiber extends to one One sister chromatid’s spindle fiber extends to one

pole, and the other extends to the opposite poles pole, and the other extends to the opposite poles (ensures a complete set of chromosomes)(ensures a complete set of chromosomes)

Anaphase: Third Phase of MitosisAnaphase: Third Phase of Mitosis

Separation of sister chromosomesSeparation of sister chromosomes– Centromeres split apart and chromatid pair Centromeres split apart and chromatid pair

separateseparate– Pulled apart by the shortening of the Pulled apart by the shortening of the

microtubules in the spindle fiber.microtubules in the spindle fiber.

Telophase: 4Telophase: 4thth phase of mitosis phase of mitosisChromosomes reach opposite poles of cell.Chromosomes reach opposite poles of cell.Prophase changes are reversed Prophase changes are reversed

(independent existence).(independent existence).Chromosomes unwind; Spindle breaks down; Chromosomes unwind; Spindle breaks down;

nucleolus reappears; new nuclear envelope nucleolus reappears; new nuclear envelope forms each set of chromosomes; new double forms each set of chromosomes; new double membrane begins to form.membrane begins to form.

CytokinesisCytokinesis Cytoplasm divisionCytoplasm division Animal Cells—Membrane is drawn inward until the Animal Cells—Membrane is drawn inward until the

cytoplasm is pinched into two nearly equal parts.cytoplasm is pinched into two nearly equal parts.

Plant Cells—(cell membrane not flexible enough to Plant Cells—(cell membrane not flexible enough to draw inward because of rigid cell wall) Cell plate draw inward because of rigid cell wall) Cell plate forms b/w the divided nuclei. Gradually, cell plate forms b/w the divided nuclei. Gradually, cell plate develops into cell membrane that separates two develops into cell membrane that separates two daughter cells.daughter cells.

Result of MitosisResult of Mitosis Two new cells with chromosome Two new cells with chromosome

sets identical to those of the sets identical to those of the parents; Carry out same function of parents; Carry out same function of parent cells; Grow and divide like parent cells; Grow and divide like parent cells.parent cells.

TissuesTissues: group of cells that work : group of cells that work together to do a specific function.together to do a specific function.

OrgansOrgans: group of two or more : group of two or more tissues organized to perform tissues organized to perform complex activities within an complex activities within an organism.organism.

Organ SystemsOrgan Systems: Multiple organs : Multiple organs that work together to perform that work together to perform specific life function.specific life function.

Cell CycleCell Cycle

Purpose of Cell Division and Purpose of Cell Division and MitosisMitosis

Keep total cell number in a mature organism Keep total cell number in a mature organism relatively constant,relatively constant,

Replace worn-out or damaged cells,Replace worn-out or damaged cells,Enable a multicellular organism to grow to Enable a multicellular organism to grow to

adult size.adult size.

Control of Cell CycleControl of Cell Cycle

Cell cycleCell cycle 24 to 48 hours 24 to 48 hours less then an hour less then an hour never divide only maturenever divide only mature

Most muscle and nerve never Most muscle and nerve never dividedivide

A mistake in the cell cycle can A mistake in the cell cycle can lead to cancer.lead to cancer.

Cell RegulationCell Regulation Injury occurs-cells divide rapidly, healing Injury occurs-cells divide rapidly, healing

process begins, as near completion, slows process begins, as near completion, slows down, everything returns to normaldown, everything returns to normal

Cyclin-a protein that regulates timing of cell Cyclin-a protein that regulates timing of cell cyclecycle

Regulatory Proteins-Proteins that control cell Regulatory Proteins-Proteins that control cell cycle (both inside and outside cell)cycle (both inside and outside cell)– Functions: slow down or stop cell division, start Functions: slow down or stop cell division, start

cell division, etc cell division, etc – Internal Regulators- allow cell to proceed only Internal Regulators- allow cell to proceed only

when certain events have occurredwhen certain events have occurred– External Regulators-Respond to events outside External Regulators-Respond to events outside

cell.cell.• Growth factors-stimulate growth and division of cells.Growth factors-stimulate growth and division of cells.

Control of the Cell CycleControl of the Cell Cycle

Enzymes Enzymes – Begin and drive the cell cycle Begin and drive the cell cycle – Control the cycle through its phases.Control the cycle through its phases.

Cell can lose control (Cell can lose control (uncontrolled uncontrolled dividing) dividing) – failure to produce certain enzymesfailure to produce certain enzymes– production of other enzymes at the wrong time.production of other enzymes at the wrong time.

Cancer is the result of uncontrolled cell Cancer is the result of uncontrolled cell division.division.

Cell DeathCell Death

Death due to injuryDeath due to injuryApoptosis-Cell may be programmed to Apoptosis-Cell may be programmed to

die (self-destruction)die (self-destruction)– Controlled steps to deathControlled steps to death

• Cell and its chromosomes shrinkCell and its chromosomes shrink• Parts of cell membrane break offParts of cell membrane break off• Neighboring cells clean up cell’s remainsNeighboring cells clean up cell’s remains

Causes of loss of control of cell Causes of loss of control of cell cyclecycle

Environmental FactorsEnvironmental FactorsChanges in enzyme productionChanges in enzyme production

– Enzyme production is directed by genes located Enzyme production is directed by genes located on the chromosome. on the chromosome.

– A A genegene is a segment of DNA that controls the is a segment of DNA that controls the production of a protein.production of a protein.

Many studies point to portion of interphase Many studies point to portion of interphase just before DNA replication as being a key just before DNA replication as being a key control period.control period.

Cancer: A mistake in the Cell Cancer: A mistake in the Cell CycleCycle

Expressed as cancer when Expressed as cancer when something prompts the damaged something prompts the damaged

genes into action.genes into action.

CancerCancer

Cancerous cells form masses of tissue called Cancerous cells form masses of tissue called tumorstumors that deprive normal cells of nutrients. that deprive normal cells of nutrients.

Late Stages: Cancer cells enter the Late Stages: Cancer cells enter the circulatory system and spread throughout the circulatory system and spread throughout the body (body (MetastasisMetastasis), forming new tumors that ), forming new tumors that disrupt the function of organs, organ disrupt the function of organs, organ systems, and ultimately the organism.systems, and ultimately the organism.

In Cancer Cells •There is no awareness of surroundings. •Cells do not stop dividing when crowded. •Cells do not stop after a set number of divisions. •Cells do not enter a resting state. •Cells divide faster and take less time to complete the cycle.

Cancer: 2Cancer: 2ndnd Leading Cause of Leading Cause of death in the United States death in the United States

(heart disease #1)(heart disease #1)Environmental and Genetic FactorsEnvironmental and Genetic Factors Cigarette smokeCigarette smoke AirAir Water pollutionWater pollution Exposure to UV RadiationExposure to UV Radiation Viral InfectionsViral Infections Instogram, Facebook and TwitterInstogram, Facebook and Twitter p53 (gene halts cell cycle)p53 (gene halts cell cycle)

TreatmentsTreatments

Surgery (tumor removal)Surgery (tumor removal)Chemotherapy-Chemical compounds that kill Chemotherapy-Chemical compounds that kill

cancer cells and/or slow growthcancer cells and/or slow growth– Interfere with healthy cellsInterfere with healthy cells– Serious side effectsSerious side effects

RadiationRadiation

Cancer PreventionCancer Prevention

Link between healthy lifestyle and the Link between healthy lifestyle and the incidence of cancer.incidence of cancer.

Diets low in fat and high in fiber.Diets low in fat and high in fiber.Minimal amounts of fat.Minimal amounts of fat.Vitamins and minerals; carotenoids, vitamins Vitamins and minerals; carotenoids, vitamins

A, C, and E and calcium.A, C, and E and calcium.Daily exerciseDaily exerciseNo smokingNo smokingDon’t use Instogram, Don’t use Instogram,

Face Book and Twitter Face Book and Twitter

Cell DifferentiationCell Differentiation

Human body-estimated one hundred trillion Human body-estimated one hundred trillion cells.cells.

Embryo-developmental stage of a Embryo-developmental stage of a multicellular organism; organism's cells multicellular organism; organism's cells become more and more differentiated and become more and more differentiated and specialized for specific function.specialized for specific function.

DifferentiationDifferentiation

During development of an During development of an organism, cells differentiate into organism, cells differentiate into

many types of cellsmany types of cells

9959 cell with precisely determined functions

Stem Cells and DevelopmentStem Cells and DevelopmentTotipotent-cells that are able to develop into Totipotent-cells that are able to develop into

any type of cell found in the body.any type of cell found in the body.Blastocyst- after about 4Blastocyst- after about 4thth day of day of

development human embryo forms; a development human embryo forms; a hollow ball of cells with a cluster of cells hollow ball of cells with a cluster of cells inside (inner cell mass); differentiation occursinside (inner cell mass); differentiation occurs– Outer cells form tissue that will attach to momOuter cells form tissue that will attach to mom– Inner cells mass becomes the embryoInner cells mass becomes the embryo

Pluripotent CellsPluripotent CellsCells that can develop into MOST, Cells that can develop into MOST,

but not all, of body’s cell types.but not all, of body’s cell types.Ex. Inner cell mass (can not form Ex. Inner cell mass (can not form

tissues surrounding embryotissues surrounding embryo

Stem CellsStem Cells

Unspecialized cells from which Unspecialized cells from which differentiated cells developdifferentiated cells develop

Stem CellsStem Cells

Embryonic Stem Cells-found in early Embryonic Stem Cells-found in early embryosembryos– 1998 researchers from way to grow in culture1998 researchers from way to grow in culture– Can make different types of cells; sperm made Can make different types of cells; sperm made

from embryonic stem cells were used to from embryonic stem cells were used to generate live mice.generate live mice.

Adult Stem CellsAdult Stem Cells

Cells that differentiate to renew and replace Cells that differentiate to renew and replace cells in the adult body-limited potentialcells in the adult body-limited potential

Multipotent-cells that can develop into many Multipotent-cells that can develop into many types of differentiated cells.types of differentiated cells.– Most only produce type of cells of given organ or Most only produce type of cells of given organ or

tissuetissue• Eg-adult stem cells in bone marrow can develop into Eg-adult stem cells in bone marrow can develop into

several types of blood cells; while brain stem cells can several types of blood cells; while brain stem cells can produce neurons (nerve cells)produce neurons (nerve cells)

Frontiers in Stem CellFrontiers in Stem Cell

Important to human healthImportant to human healthUse of undifferentiated cells to repair or Use of undifferentiated cells to repair or

replace badly damaged cells and tissues.replace badly damaged cells and tissues.Ethical IssuesEthical Issues

– Embryonic stem cells (from early embryos)Embryonic stem cells (from early embryos)• Embryo‘s entitled to rights and protections of human Embryo‘s entitled to rights and protections of human

beings.beings.• Government funding-political issueGovernment funding-political issue• Ethical issue of life and deathEthical issue of life and death

– Technology solutions becoming availableTechnology solutions becoming available