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26 Cards in this Set

  • Front
  • Back
Transport of non-lipid soluble molecules across cell membrane
1) Pores
2) Channels
3) Transporters
- non gated channel
- always open (may be regulated)
- movement via diffusion down gradient (concentration, electrical, chemical)
- only small molecules can pass
- gap junctions - connexins
- aquaporin - selective for water
- ECM to ICM
- complex can be open or closed with gate at a specific end of channel
- open state regulated
- little energetic interaction between channel and molecule
- selective
- movement due to diffusion across a gradient
Classification of Channels
- mechanical ex. stretch activated Ca channels in vascular smooth muscle
- ligand gated ex. acetylcholine activated Na- channels
- voltage gated ex. Na ion channel in nerve
- ion channel with 2 gating domains
- open state determined by physical interaction of molecule with transport protein
- only one gate open at a time
- must bind to transport protein (induces a conformational change in it)
- movement can be against gradient
- selective
- 2 or more molecules move toeghter in the same direction
- must have both to transport
- 2 or more molecules move in opposite directions
- must have both to transport
primary active transport (pump)
- transport protein is an enzyme that uses ATP to move one or more molecules across cell membrane
- move against electrochemical gradient
secondary active transport
- transporter NOT an enzyme
- uses [ ] gradient established through active transport to move molecule against a gradient
Movement of molecules via pores and channels
1) rate of transmembrane flux dependent on electrical and chemical gradients
2) does not saturate
3) faster rate than movement via transporters
Movement of molecules via transporters
1) max flux rate is limited by # of available transport proteins
2) transporter saturates
3) characterized by Km and Vmax
- covalently binds to voltage gated Na channels in nerves
- channels don't open so, action potentials can't propagate
- blocks Ca channels in cardiac and vascular smooth muscle
- inhibits Na-K pump in cardiac muscle
malignant hyperthermia
- altered muscle Ca channel
- excessive muscle contractions
- defective Cl or Na channels
Long QT Syndrome
- alteration in electrical conduction in the heart
- defective K or Na channels
- aquarporin channels, passive diffusion
- [ ]= # of solute molecules in a given molecule
- mosmoles/L
- more solute = lower [H2O]
osmotic pressure
- Pressure needed to prevent water movement
- 1 mosmoles/L = 19 mmHg
-Osmolarity of extracellular and intracellular fluids is approximately 290 mosmoles/L, which is an osmotic pressure of 5,510 mmHg
isoosmotic solution
- solution with the same osmolarity of the cell
- same # of solute molecules per volume of H20
- solution has same number solute molecules as cell
- no change in cell volume
- solution has fewer solute molecules than cell
- water enters cell
- solution has more solute molecules than cell
- water exits cell
Gibbs-Donnan Equilibrium
- intracell osmolarity is greater than extracellular due to negatively charged impermeable protiens
- cells swell unless osmotic work maintained
Osmotic work
- Na-K pump 3 Na out for 2 K in
- reduces number of osmotic particles
Gibbs-Donnan on Capillaries
- negatively charged blood protein repels negative permeant ions
- interstitial negative ion content (Cl) slightly greater than blood