Cell Growth and Reproduction Chapter 5. Limits to Cell Size Cell is too small: Cell is too small: Not enough room for organelles and molecules Not enough

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  • Cell Growth and ReproductionChapter 5

  • Limits to Cell SizeCell is too small:Not enough room for organelles and moleculesAs a cell grows, its volume increases much faster than its surface area.Cell is too big: Diffusion of molecules will be too slow.

  • Why cant most organisms be just one giant cell?Diffusion limits cell sizeDNA limits cell sizeSurface area-to-volume ratioAs cells size increases, its volume increases much faster than its surface area

  • Cell ReproductionChromosomes: Structures that contain DNADark when stained.Carriers of genetic material (passed from generation to generation.)Typically exist as chromatin (long strands of DNA wrapped around proteins.)

  • The Cell CycleOccurs in Eukaryotic CellsRegular pattern of: GrowthDNA duplication cell division 4 Stages in the cell cycle:Gap 1 (G1), Synthesis, Gap 2 (G2), MitosisEnzymes control the transfer through the stages

  • Gap 1 (G1)First StageCell carries out normal functionsCell increases in sizeOrganelles increase in number

  • SynthesisSecond StageSynthesis = the combining of parts to make a wholeCell makes a copy of its DNA

  • Gap 2 (G2)Third StageSimilar to G1 phaseIncludes a critical checkpoint the cell will only reproduce if everything is in order.

  • The Cell CycleThe sequence of GROWTH and DIVISION of a cell:Interphase Growth stage of cell cycleMitosis Division stage of cell cycle.ProphaseMetaphaseAnaphaseTelophaseCytokinesis process in which cells cytoplasm divides

  • InterphasePrecedes MitosisIncludes G1, Synthesis, and G2 stagesMost of a cells life is spent in this growth stageChromosomes are duplicated in preparation for cell division

  • ProphaseFirst and longest stage of MitosisChromatin uncoils to form visible chromosomesChromosomes composed of two halves called sister chromatidsSister chromatids are held together by a centromere.Nuclear Envelope disintegrates (disappears)Centrioles and spindles help in chromatid separation

  • PROPHASE

  • Metaphase2nd phase of mitosisChromosomes move to the equator Each sister chromatid is attached to its own spindle fiberSpindle fibers are attached to centromere

  • METAPHASE

  • Anaphase3rd phase of mitosisCentromeres are splitSister Chromatids are pulled apart

  • ANAPHASE

  • Telophase4th and Final stage of MitosisChromatids reach opposite poles of the cellTwo distinct daughter cells are formedProcesses of prophase are reversed

  • TELOPHASE

  • Results of MitosisCreates two new cells from original: Chromosome sets are identical to parent cell.Guarantees genetic continuityCreates tissues, organs, and organ systems

  • InterphaseMetaphaseAnaphaseTelephase/Daughter CellsProphaseMitosis of an onion cell

  • Mitosis of a White Fish Blastula Cell

  • What is Cancer2nd leading cause of death in U.S. of men and 1/3 of women develop it200 different typesRisk can be reduced by lifestyle changes

  • Normal Cell OrganizationGroups of cells form organs which produce functions.Early in life, cells divide frequentlyLater in life, cells only grow and divide to replace old cells or repair injuries

  • Cancer Cell OrganizationAbnormal Cells (mutated DNA or dont perform proper function)Inherit damaged DNA from ParentsDamaged by exposure to something (sunlight, smoking, etc.)Out of control cell multiplication; forms mass of cells (tumors)