PSIO 303A Lecture Notes - Lecture 23: Ion Transporter, Gastrointestinal Tract, Electrochemical Gradient
24 Oct 2016
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Block 2 - lecture 8 - secondary active transport. Following up on last week"s lecture on carrier mediated processes. We will know continue on secondary active transport: Transport is selective and saturable (it"s still carrier-mediated) Source of energy is not atp, it"s the potential energy available in the transmembrane gradients of one or more other solutes. Coupling that involves substrates moving in the same direction. In a few cell types (e. g. intestinal mucosa and renal proximal tubule) uptake of glucose from an extracellular solution can occur against glucose gradient (even though most cells have glucose uptake via facilitated diffusion) Uptake of glucose against concentration gradient, permits net absorption of glucose from a tissue compartment where the glucose concentration may be lower that than of the blood. Couples the flow of na+ and glucose, energy is derived from inwardly directed gradient of na+ The driving force includes: chemical gradient for na+ electrical potential difference (pd) across the membrane.
