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Cell Structure and Function
Chapter 7
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Cell History Robert Hooke (1635-1703)
Viewed slices of cork under a crude compound microscope He saw boxes which reminded him of cells that monks lived in Hence the name “cell”
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Hooke’s Microscope
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Cell History Anton van Leeuwenhoek (1632-1723)
Designed an early microscope First to see living organisms in a drop of water
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Cell History Robert Brown (1773-1858)
Used special stains and dye to view nucleus
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Cell History Theodor Schwann, zoologist, (1810-1882)
Rudolph Virchow, physician ( ) Mathias Schleiden, botanist ( )
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Cell Theory Schleiden, Schwann and Virchow each contributed to the cell theory (1838-9): Cells are the basic unit of structure and function of all living things All living things are composed of one or more cells New cells are produced from existing cells
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Cell Types Prokaryotic Eukaryotic
First appear in fossil record 3.5 BYA No membrane bound organelles Bacteria Eukaryotic Evolved 1.5 BYA Have membrane bound organelles Protists, fungi, animals, plants
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Cell Structures Cell Wall
Found in plants, fungi, algae, and most bacteria Rigid Provide structure and protection Composed of cellulose or chitin
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Cell Structures Cell Membrane Selectively permeable Flexible
Regulates what goes in and out Flexible Provides protection and support Made of a lipid bilayer
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Cell Membrane Regulates what goes in and out of the cell – SELECTIVE PERMEABILITY Wastes and cell products need to exit CO2, O2 (in plants), hormones Nutrients need to enter Sugar, O2, CO2 (in plants), amino acids Lipid Bilayer
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Phospholipids Fatty acid tails are non-polar Heads are polar
Tails don’t want to be near water because water is polar Polar ♥ Polar Non-polar ≠ Polar
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Cell Membrane Fluid Mosaic Model
Fluid: in motion -Mosaic: different stuff Outside of cell Inside (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains
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Cell Transport Substances need to cross the CM
Some molecules are small and non-polar → don’t require energy O2, CO2 Some molecules are polar or too big to cross CM → do require energy Proteins, sugars
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Diffusion Movement of molecules from an area of high concentration to low concentration Small, non-polar molecules will diffuse across CM DOES NOT REQUIRE ENERGY!! = Passive Transport
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Dynamic Equilibrium Dynamic = changing, moving Equilibrium = balanced
Molecules will diffuse until dynamic equilibrium is reached Molecules will continue to move
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Osmosis Diffusion of water across a membrane
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Osmosis High water to low water Fresh water to salt water
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Hypotonic Solution ‘Hypo-’ means less
Concentration of solute (dissolved solids) is less outside of cell than inside Water will enter cell Cell may lyse (burst) Cell wall prevents lysis in plant cells
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Hypertonic Solution ‘Hyper-’ means more
Concentration of solute is higher outside of cell Cell will lose water Plasmolysis results in plant cells
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Isotonic Solution ‘Iso-’ means equal
Solute concentration is the same outside and inside the cell No change in cell size Animals prefer this
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Facilitated Diffusion
Large molecules moving down their concentration gradient use a protein to facilitate (help) their crossing the CM Diffusion = no energy!
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Facilitated Diffusion
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Active Transport Requires energy
Used for large molecules or substances moving against their concentration gradient (low to high) Exocytosis – exiting cell Endocytosis – entering cell
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Active Transport
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Endo- and Exocytosis
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Levels of Organization
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