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Membrane Physiology
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Membrane Physiology

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  1. Membrane Physiology 1. Label the “circles”. What are they called? 2. Label the “squiggly lines”. What are they called?

  2. Simple Diffusion O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 O2 Until equilibrium is reached

  3. FacilitatedDiffusion (Channels) Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Until equilibrium is reached

  4. Ligand (Chemically) – Gated Channels Na+ Na+ ligand Na+ ligand Na+ Na+ Na+ Na+ Na+ Nothing happens! Na+ Na+ Na+ Until equilibrium is reached

  5. Normal Cell Membrane Potential - + Ca2+ Ca2+ - + Ca2+ - + Ca2+ Ca2+ - + - + Ca2+ INSIDE OUTSIDE - + Ca2+ Ca2+ Ca2+ - + Ca2+ - + Ca2+ Ca2+ Ca2+ interior of cell is NEGATIVELY charged - + Ca2+

  6. Voltage-Gated Channels + - + Ca2+ + - + Ca2+ Ca2+ + - + Ca2+ + - + Ca2+ + - + Ca2+ INSIDE OUTSIDE + - + Ca2+ Ca2+ + - + Ca2+ Ca2+ + - + Ca2+ Ca2+ channel opens because of a voltage change INSIDE the cell Ca2+ + - + Ca2+

  7. Back to Biochemistry… • diffusion (passive, through PLBL) • facilitative diffusion (passive, through channels) • channels come in several flavors: • ligand-gated • voltage-gated • more about gradients… • pumps (active)

  8. Chemical Gradient Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+

  9. Electrical Gradient - + + - + + + + - + + - + + Initially: 5 + charges on either side of the membrane Initially: 1 – charge on left, 3 – charge on right

  10. ElectrochemicalGradient - Cl- Na+ Na+ Na+ Cl- Na+ Na+ Cl- Na+ - Na+ Na+ Na+ Cl- Na+ Initial: 5 Na+ on each side & 2 Cl- on each side

  11. The Bottom Line on Gradients • ions will travel DOWN their electrochemical gradients until chemical AND electrical equilibrium has been reached

  12. Pumps ATP Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl- Cl-

  13. ATP (Adenosine TriPhosphate ADENOSINE P P P 1 2 3

  14. ATP Stores Energy in Bonds ADENOSINE P P P RELEASING ENERGY! 1 2 3 + ADENOSINE P P P 1 2

  15. ADP (Adenosine Diphosphate) + ADENOSINE P P P 1 2 (lone phosphate)

  16. Recycling ATP from ADP ADENOSINE P P P 1 2 3 Phosphorylation + ADENOSINE P P P 1 2