BIOL130 Lecture Notes - Lecture 10: Glycerol, Active Transport
22 Oct 2015
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Biol 130 lecture 10 unit 6 biological membranes ctd. Membrane semipermeability: small nonpolar molecules diffuse most readily, o2, co2, n2, steroid hormones, small uncharged polar molecules: do not cross as readily, h2o, ethanol, glycerol. Larger uncharged polar molecules: most do not pass directly through: amino acids, glucose, nucleosides. Ions: smallest in size, but overtly charged; none can diffuse readily: h+, na+, k+, ca2+, cl-, mg2+, hco3. Passive vs active transport: passive: no energy is required, goes with the concentration gradient, active: requires energy, goes against the concentration gradient. What determines whether channels are open or closed: voltage gated: the inner side is sensitive to charges. Transporting against a gradient: active transport, coupled movement using atp energy to move ions against the concentration gradient, eg. Sodium-potassium atpase: moves sodium in and potassium out in animal cells, helps to maintain the sodium gradient needed to move other molecules (glucose, amino acids)
