"Trust me, I'm an improviser" (c) Owen Harper
Transporters, pumps and channels
- Cell controls what enters it using subj. for charged molecules.
- The way diuretics (мочегонное) work is they inhibit the ability of transporters to move chloride across cell membrane, which inhibits water movement, which means extra water gets peed out, so blood pressure drops.
- Few ways to move stuff around:
-- Simple diffusion - random movement of hydrophobic uncharged molecules through the lipid membrane.
--- From high to low concentration.
--- No energy required.
--- Fast over short distances, but too long over long distances.
--- Faster at higher temperatures.
--- Inversely related to the size of the molecule.
--- Depends on the total surface area and the thickness of the membrane barrier.
-- Gap junctions - permit diffusion of ions between coupled cells.
-- Transporters - two-way gates, opens only one way at a time - facilitated diffusion, so it’s still a movement mainly from high to low concentration.
--- Specific to the molecule.
--- Finite number on the membrane - can be saturated.
--- Co-transporters - move two solutes at the same time.
---- Symporter - same direction.
---- Antiporter - opposite direction.
-- Channels - holes that go through the membrane. Can be closed by a gate. When open, a movement is through diffusion from high to low concentration.
--- Ligand/chemical gate - channel only opens in presence of some specific chemicals.
--- Voltage - requires a specific charge to open.
--- Mechanical - requires tension to open.

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