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Unformatted text preview: High Glucose High H + Biology 2A03 L5 Lecture 5 T ransport Mechanisms I I Channel Proteins 1. Selective for type of ion ; transmembrane 2. Ex. K + channels, Ca 2+ channels 3. Due to size and the charged and polar surfaces of the protein subunits of the channels 4. Electrically attract or repel particular ions 5. Consist of polypeptides surrounding a central core 6. Opening of the pore can be regulated (e.g. membrane potentials regulates voltage-gated channels) 7. Membranes as being a selective barrier by the types and # of these channels in this membrane 8. Ex. As membrane potentials change in neurons, channels begin to open/close 9. Action potential how information is transmitted in neurons through electrical signals 2 . b) Facilitated Diffusion 1. Actually a mediated transport 2. Net flu of molecules across membranes is from high to low concentration or downhill movement 3. Not coupled with ATP hydrolysis to move molecules in the opposite direction (i.e. low to high ) 1 Biology 2A03 L5 1. called facilitated because it involves a membrane transport 2. glucose-6-phosphate- keeps concentration of glucose low in cell by converting it, allowing more glucose to keep flowing into cell, thus there is always a big concentration gradient (first step in glycolysis) 3. differs from simple diffusion in that it involves selective membrane...
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