Unit 7: Cell Growth and Division

10-1 Cell Growth10-2 Cell Division10-3 Regulating the Cell CycleUnit 7: Cell Growth and Division10-1 Cell GrowthWhy do cells divide rather than getting larger in size?Demands on information from the DNA becomes too greatThe cell has difficulty moving enough nutrients and wastes across the cell membrane

10-1 Cell Growth: Division of the CellThe process by which a cell divides into two new daughter cells is called cell divisionBefore division occurs a cell must:Copy its DNA

10-2 Cell DivisionWhy do cells divide?To repair damaged or old cellsSo the organism can get larger (grow)

10-2 Cell DivisionBefore a cell can divide it must make a copy of its entire chromosome so that it can pass it on to the two new cells created by division.Eukaryotic cell division is complex and involves two main stages:Mitosis the division of the nucleusCytokinesis the division of the cytoplasm

10-2 Cell DivisonChromosomesGenetic information in eukaryotic cells is organized into chromosomes.Chromosomes are only visible (with a light microscope) during cell division, it is then that they pack tightly into a dense visible structure.Chromosomes are copied before divisionCopied chromosomes consist of two identical sister chromatids held together by an area called the centromere.

Parts of a Homologous Pair of Chromosomes

CentromereChromosomeChromatidHomologous Chromosomes10-2 Cell DivisionThe Cell CycleScientists describe the events in the life of the cell as the cell cycle.During the cell cycle the cell grows, prepares for division, and divides to form two daughter cells which will then re-enter the cell cycle from the beginning.

The Cell CycleThe cell cycle has four phases:G1S phaseG2M phase

10-2 Cell DivisionEvents of the Cell CycleStage 1: InterphaseGap 1Synthesis PhaseGap 2Stage 2: Mitotic Phase (Cell Division)MitosisProphaseMetaphaseAnaphaseTelophaseCytokinesis

10-2 Cell DivisionInterphaseGap 1: cells grow, make proteins and organellesSynthesis phase: DNA replication takes placeGap 2: cell grows organelles and molecules need for replication are produced

Mitosis: The division of the nucleusProphaseChromosomes become visible Centrioles separate and move to opposite ends of the cell The spindle (a structure that helps to separate the chromosomes) formsNucleolus disappears and nuclear envelope breaks down

MetaphaseMicrotubles attach to the centromeres to move the chromosomesChromosomes line up in the center of the cell

Mitosis: The division of the nucleusAnaphaseCentromeres that join sister chromatids split in halfSister chromatids split and become individual chromosomesChromosomes move to opposite poles of the cell

TelophaseChromosomes begin to disperse and are less visibleNuclear envelopes begin to reform around each cluster of chromosomesThe spindle fibers dissolve

Mitosis

At the end of InterphaseProphaseMetaphaseAnaphaseTelophaseBlood lilly MitosisAt the end of InterphaseProphaseMetaphaseAnaphaseTelophase1410-2 Cell DivisionCytokinesisThe result of Mitosis is the formation of two nuclei each with duplicate sets of chromosomes formed within the cytoplasm of a single cell.Cytokinesis separates the cytoplasm of the cell into two.During cytokinesis in plant cell a cell plate forms between the nucleiDuring cytokinesis in animals a cleavage furrow forms pinching the two cells apart

Do You Know the Stages of Mitosis?

CYTOKINESISPROPHASEANAPHASEANAPHASEINTERPHASEMETAPHASETELOPHASE1610-3 Regulating the Cell CycleControls on Cell Division:When cells come in contact with other cells they usually respond by not growingIf cells are scraped away the cells bordering the gap will divide and fill the open space.This means that cell division can be turned on and off depending on the environment around the cell.

10-3 Regulating the Cell CycleCell cycle regulators:Cyclins are one type of protein that regulates the timing of the cell cycleInternal regulators: proteins that respond to events inside the cellProteins that prevent mitosis from happening without all of the DNA being copied firstExternal regulators: proteins that respond to events outside the cellGrowth factors are proteins that trigger cell division during healing and embryonic developmentSome proteins on the outside of cells slow down or stop cell cycles of nearby cells

Uncontrolled Cell GrowthCancer is a disease caused by cells that do not respond to the signals that regulate growth.According to the American Cancer Society:As of 2008 in the United States of America a man has a 1 in 2 chance of developing cancer in his lifetime and a woman has a 1 in 3 chance of developing cancer in her lifetimeCancer accounts for 1 in 4 deaths in the U.S. each year.What Causes Cancer?Gene changes due to: diet tobacco use exposure to radiation exposure to chemicals Inherited genes (cyclins/growth factors dont work)

Immune System Failure

Carcinogens

21Allergic reactions swelling itching also flu like symptoms greatest concern is extreme allergic reactionsBiological Therapy:Elicits a response from your immune system (helps immune system fight cancerous cells)Weakening of the bones can -effect sex characteristicsHormone Therapy:Blocks hormones that cancer needs to growSimilar to radiation therapyChemotherapy: Chemicals target cancer cells given 2 or more at a timeCan injure or kill healthy cellsRadiation Therapy:Damages cancer cells DNA, cells wont reproduceRestricted to a few types of cancer - may not get all cells-damages organsSurgery: physically remove tumor

Side EffectsTreatment22Cancer Among MenThe three most common cancers among men include:Prostate cancerLung cancerColorectal cancerThe leading causes of cancer death among men are:Lung cancerProstate cancerLiver cancer

Cancer Among WomenThe three most common cancers among women include:Breast cancerLung cancerColorectal cancerThe leading causes of cancer death among women are:Lung cancerBreast cancerColorectal cancer