NPB 10 mt 1

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NPB 10 mt 1
2012-02-07 23:35:53

Lecture 5
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  1. Concentration gradient
    differences in the number of molecules or ions of a substance between neighboring region
  2. Diffusion
    • -the net movement of susstances down a concentration gradient
    • -passive transport-does not need energy
    • -each solute moves down its own gradient
    • -Individual modlecules move around whether or not there is a gradient- Brownian movement
    • -moves through semipermeable membrane
  3. Osmosis
    • -water crosses membranes- diffusion of water across a plasma membrane
    • -three types of condition: hypotonic (more water), hypertonic (less water), isotonic (same amount of water and sucrose)
  4. Hypotonic conditions
    water diffuses in; the cells swell up
  5. Hypertonic condition
    water diffuses out; the cells shrink
  6. Isontonic condition
    no net change in water movement or cell shape
  7. Plasma Membrane
    • -selective permeability
    • -small, nonpolar substances slip across
    • ( oxygen and carbon dioxide)
    • -water (polar) slowly slips through gaps
    • -use of transport proteins for: ions, large polar molecule, e.g., glucose (they cannot pass through on their own)
  8. other mechanisms that substances also cross cell membrane
    • 1. facilitated diffusion (passive transport, no ATP, transport proteins)
    • 2. active transport (ATP, membrane pumps)
    • 3. exocytosis, and
    • 4. endocytosis
  9. endocytosis
    a vescile brings substances in bulk into the cell
  10. exocytosis
    a vesicle ejects substances in bulk from the cell, the cell expelled
  11. metabolism
    • most chemical reactions in cell, maintain homeostasis
    • -some reaction release energy
    • -some reaction require energy
  12. ATP/ADP cycle
    • cells use ATP constantly
    • ATP must be replenished
    • phosphate bonds store energy