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Published byTalon Birchard Modified over 9 years ago
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Membrane Transport
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3 Types of transport
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Passive Transport Simple diffusion –Small non-polar molecules No ions –Examples: Fatty acids Steroids CO 2 O 2 H 2 O (?)—osmosis –Only move DOWN concentration gradient
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Osmosis
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Osmosis, con't.
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Mediated Transport Passive mediated transport –Facilitated diffusion Carrier proteins Channel proteins –DOWN a conc. gradient Active transport –Primary active transport—uses ATP –Secondary active transport—uses a different energy source –Pumps things UP a conc. gradient
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How to tell mediated transport vs. simple diffusion Saturation kinetics Competition kinetics Specificity
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Some more terms
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GluT1 (RBCs)—a carrier protein
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Channel proteins Ion channels –Ions –Selective –Generally gated Porins –Larger –Less specific Aquaporins –water
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Porins
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The Pore-Forming Toxins Lethal molecules produced by many organisms Insert themselves into the host cell plasma membrane Kill by –collapsing ion gradients –facilitating entry by toxic agents –introducing a harmful catalytic activity
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Colicins Produced by E. coli Inhibit growth of other bacteria (even other strains of E. coli) Single colicin molecule can kill a host!
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Other Pore-Forming Toxins Hemolysin from –Staphylococcus aureus –a symmetrical pore Aerolysin –Aeromona hydrophila Anthrax toxin protective antigen –Bacillus anthracis
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Hemolysin
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Ionophore Antibiotics
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Valinomycin Cyclic peptide Valinomycin- potassium complex diffuses freely and rapid across membranes
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Gramicidin—pore forming
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Active Transport
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Direct and Indirect AT
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The Na/K ATPase
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Consequences of Na/K ATPase Two ion gradients –Used as energy source –Electrical signaling Charge difference across membrane –Membrane potential difference –Negative on inside -60 to –90 mV in animal cells ~ -150 mV in bacteria -200 to –300 mV in plants –Not just due to these ions Phosphatidylserine on inside of PM Other ions
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Indirect (secondary) AT Na/glucose symporter –Intestinal absorptive cells
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Energetics of Transport
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Thermodynamics of Transport, charged
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