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Cell Structure and Function

Cell Structure and Function. The Cell Theory. All living things are made of one or more cells All cells come from pre-existing cells Cells are the basic unit for structure and function of all organisms. Cell structure. All cells are surrounded by a plasma (cell) membrane

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Cell Structure and Function

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  1. Cell Structure and Function

  2. The Cell Theory • All living things are made of one or more cells • All cells come from pre-existing cells • Cells are the basic unit for structure and function of all organisms

  3. Cell structure • All cells are surrounded by a plasma (cell) membrane • Cells contain organelles - small structures inside cells that perform various jobs • All cells can be divided into two main categories:

  4. Prokaryotic no nucleus Very small (1-10 um) Have very few organelles Eukaryotic have a nucleus Larger 10-100um (some larger) Have many organelles Prokaryotic vs. Eukaryotic Cells

  5. Eukaryotic Cells • Plant and animal cells are eukaryotic as well fungi and protists (amoeba, paramecium, etc) • Plant and animal cells have important differences (see diagrams)

  6. Eukaryotic Cellular Organization • Single celled organisms (unicellular) • Multiple celled organisms (multicellular) - in multicellular organisms, cells become specialized (do a particular job)

  7. Plasma (cell) membrane • Consists of a double layer of lipids • The outside and inside of the membrane is hydrophilic (“water-loving”) • The interior of the membrane is hydrophobic (“water-fearing”) • Substances must cross the membrane to enter and exit the cell

  8. Types of Membrane Transport Passive Transport (requires NO energy) • Moves substances from a high to a low concentration • Diffusion & osmosis, facilitated diffusion Active Transport (requires energy) • Substances move from a low to a high concentration • Endocytosis & exocytosis

  9. Concentration gradient • Passive transport moves substances WITH (or DOWN) their concentration gradient • Active Transport moves substances AGAINST their concentration gradients PASSIVE TRANSPORT HIGH LOW ACTIVE TRANSPORT

  10. Diffusion • Movement of a substance from a high concentration to a low concentration

  11. Osmosis • Movement of water from a high water concentration to a low water concentration

  12. Osmosis in Different Cellular Environments • Hypotonic - solution with a lower solute concentration than the cytoplasm of the cell • Hypertonic - solution with a higher solute concentration than the cytoplasm of the cell • Isotonic - has same solute concentration as the cytoplasm of the cell

  13. Turgor pressure - pressure (from water) pushing against the cell wall of a plant (makes plant cells firm) • Plasmolysis - shrinking of the cytoplasm of a cell caused by the loss of water (causes plants to wilt)

  14. Facilitated Diffusion • Diffusion using membrane protein channels • Some substance must use protein channels since they cannot pass through the lipid layer of the membrane

  15. Active Transport • Requires the input of energy to move a substance against its concentration gradient (low to high) • Energy is used in the form of ATP (energy molecule produced in mitochondria)

  16. Types of Active Transport: Endocytosis, Exocytosis and Ion Pumps • Endocytosis - cell takes in substances too large to pass through the membrane • Exocytosis - cell gets rid of large substances • Ion pumps - pump ions against their concentration gradient See endocytosis and exocytosis in action

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