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Lecture 4

Second Half Lecture 4.doc


Department
Biology
Course Code
BIO130H1
Professor
Jane Mitchell
Lecture
4

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Lecture 4 Mar. 8/12
Membrane Transport of Small Molecules
Transport of glucose from intestine to blood stream
Terminology
Glucose movement: intestinal lumen intestinal epithelium extracellular fluid
Glucose concentrations: Intestinal lumen (L), intestinal epithelium (H), extracellular
fluid (L)
The transition requires going through a connecting cell attached to intestine outside
Apical domain of cell faces intestinal lumen
Basal domain of cell faces extracellular fluid
Lateral domain of cell faces intestinal epithelium
Basal + lateral = basal-lateral domain
Tight junctions prevent movement of material between adjacent cells
Transport process
Small molecule movement must go through cells due to tight junctions
Na+/glucose symporter on apical side moves glucose from low to high concentration
Movement of glucose against gradient utilizes Na+/K+ pump on basal-lateral domain
Na+ levels are kept low (away from equilibrium) by Na+/K+ pump in cell
Glucose goes through GLUT uniporter on basal-lateral domain into extracellular fluid
ATP-driven pumps (transport ATPases)
Overview
Help establish a gradient
Important towards resting membrane potential
Osmotic balance
Includes P-type ATPase, Na+/K+ pump
F-type
Use H+ gradient to produce ATP
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