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The Cell

The Cell. Marlene Smith IB Biology HL. Introduction. The cell is as fundamental to Biology as the atom is to Chemistry. Simplest collection of matter that can live. Everything an organisms does occurs at the cellular level All cells are related by their descent from earlier cells.

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The Cell

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  1. The Cell Marlene Smith IB Biology HL

  2. Introduction • The cell is as fundamental to Biology as the atom is to Chemistry. • Simplest collection of matter that can live. • Everything an organisms does occurs at the cellular level • All cells are related by their descent from earlier cells.

  3. Cell Theory • All organisms are composed of 1 or more cells. • The cell is the basic functional unit of life; all the chemical reactions of life occur in the cell. • New cells arise from pre-existing cells. • Cells contain inherited information (genes)that control growth, functioning and reproduction.

  4. Historical Perspective • Development of Cell Theory II Invention of the Microscope • 1665-Van Leeuwenhoek(microbes) and Hooke(cells in cork) • 1830’s-Scwhann & Scleiden-all animals& plants are made of cells • 1855-Virchow-cells come from cells • 1900’s-chromosomes carry genetic infomation

  5. Microscopes • Most important tool of Cytology • 2 impt. Values in Microscopy Magnification: how much larger object appears than with naked eye-enlargementResolution: inversely related to wavelength of radiation used by the microscope-ability to distinquish between 2 separate points • Types - Advantages • Light • Electron : TEM & SEM

  6. Inexpensive simple to use natural colors living specimens magn = 1000X max.= 0.2um wavelength of light = .4 - .7 um Expensive complex to use false colors dead organisms mag=100,000X max.=.002um view internal components of organelles Light v. Electron

  7. Organelles • Carry out life functions • Require an EM for study of ultrastructures • Comparative Sizes • ribosomes = .1 um • nucleus = 10-20 um

  8. Comparative Sizes of • Molecules • DNA nucleotide - .002 um • cell membrane - .007 um • virus • organelle 0.1-10 um • prokaryote cell - 1 - 5 um • eukaryote cell - 20-50 um

  9. Factors that limit cell size • Cell exchange materials with environment by diffusion • Rate of Diffusion is slow - rate decreases from source • As Cell Surface area is doubled the Volume is cubed • decrease in surface to volume ratio reduces efficiency • the larger the cell the less efficient the transport

  10. Multicellular Organisms and Large Cells overcome diffusion problem by • Flattened shape • protrusions- ex. villi in small intestine • develop specialized organs for transport of substances ex. red blood cells & conducting tubes inplants

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