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Lectures 15 Membrane Structure and Transport-BW

Imbedded in the bilayer they can only be removed from

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Unformatted text preview: ing the membrane (organic solvents, or strong detergents) Often transmembrane but not necessarily 3/11/13 MCB 2000 Lectures 15 Dont ahve a lot of structureal info about the membrane protein - but is that relaly the s tructure in the membrane and will it function - needs hydrophoibc interaction to fold properly Lipid-Anchored Membrane Proteins Glycosyl phosphatidylinositol anchors prion protein is an example of this type of proteinmembrane interaction 3/11/13 MCB 2000 Lectures 15 How Does Transport Occur Across Biological Membranes? 3/11/13 MCB 2000 Lectures 15 Types of Transport Mechanisms Simple diffusion Facilitated (passive) diffusion Gated channels Active transport Distinguished by: concentration gradient, requirements for protein carrier (transporter) and ATP You should be able to specifically distinguish between the different transport mechanisms for an exam question. 3/11/13 MCB 2000 Lectures 15 Active Transport: Na,K-ATPase as an Example 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 3/11/13 MCB 2000 Lectures 15 Na,K Transport Congestive heart failure and cardiotonic steroids (digitalis) Hypertension involves apparent inhibition of sodium pump. Inhibition in cells lining blood vessel walls results in Na, Ca accumulation 3/11/13 MCB 2000 Lectures 15 The parietal cells of the gastric mucosa (lining of the stomach) have an internal pH of 7.4 The Gastric H+,K+-ATPase H+,K+-ATPase pumps protons from these cells into the stomach to maintain a pH difference across a single plasma membrane of 6.6! This is the largest concentration gradient across a membrane in eukaryotic 3/11/13 organisms! MCB 2000 Lectures 15 Transport processes driven by ion gradients Many amino acids and sugars are accumulated by cells in transport processes driven by ion gradients 3/11/13 MCB 2000 Lectures 15...
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