Membranes have proteins that mediate and regulate the transport of metabolites, macromolecules, and ions. Hormones and many other biological signal molecules and regulatory agents exert their effects via interactions with membranes. Photosynthesis, electron transport, oxidative phosphorylation, muscle contraction, and electrical activity all depend on membranes and membrane proteins. What are the properties and characteristics of biological membranes that account for their broad influence on cellular processes and transport? | Chapter 10 Membrane Transport to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 Outline Passive Diffusion Facilitated Diffusion Active Transport - Transport Driven by ATP, light, etc. Group Translocation Specialized Membrane Pores Ionophore Antibiotics Passive Diffusion No special proteins needed Transported species simply moves down its concentration gradient - from high [c] to low [c] Be able to use Eq. and High permeability coefficients usually mean that passive diffusion is not the whole story Facilitated Diffusion G negative, but proteins assist Solutes only move in the thermodynamically favored direction But proteins may "facilitate" transport, increasing the rates of transport Understand plots in Figure Two important distinguising features: solute flows only in the favored direction transport displays saturation kinetics Active Transport Systems Energy input drives transport Some transport must occur such that solutes flow against thermodynamic potential Energy input drives transport Energy source and transport machinery are "coupled" Energy source may be ATP, light or a concentration gradient The Sodium Pump aka Na,K-ATPase Large protein - 120 kD and 35 kD subunits Maintains intracellular Na low and K high Crucial for all organs, but especially for neural tissue and the brain ATP hydrolysis drives Na out and K in Alpha subunit has ten transmembrane helices with large cytoplasmic domain Na,K Transport ATP hydrolysis occurs via an E-P intermediate Mechanism involves two enzyme conformations known as E1 and E2 Cardiac glycosides inhibit by binding to outside Na,K Transport Hypertension involves apparent inhibition of sodium pump. Inhibition in cells lining blood Vessel walls results | Chapter 10 Membrane Transport to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 Outline Passive Diffusion Facilitated Diffusion Active Transport - Transport Driven by ATP, light, etc. Group Translocation Specialized Membrane Pores Ionophore Antibiotics Passive Diffusion No special proteins needed Transported species simply moves down its concentration gradient - from high [c] to low [c] Be able to use Eq. and High permeability coefficients usually mean that passive diffusion is not the whole story Facilitated Diffusion G negative, but proteins assist Solutes only move in the thermodynamically favored direction But proteins may "facilitate" transport, increasing the rates of transport Understand plots in Figure .
