Chapter 5 - Brooker CH 5 Membrane Structure and Transport...

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Brooker CH 5 Membrane Structure and Transport Membrane structure and function 0. Overview: Life at the Edge 1. The plasma membrane 0. Is the boundary that separates the living cell from its nonliving surroundings 2. How does the plasma membrane keep some substances out but allow other substances in? 0. And vice versa Membrane structure and function 0. Biological Membranes 0. Act as selective barrier 1. Detect chemical messengers at cell surface 2. Link adjacent cells together by membrane junctions 3. Anchor proteins 4. Separate living cell from nonliving surroundings Membrane structure and function 0. Cellular membranes are fluid mosaics of lipids and proteins 1. Phospholipids 0. Are the most abundant lipid in the plasma membrane 1. Are amphipathic, containing both hydrophobic and hydrophilic regions The Fluidity of Membranes 2. Phospholipids in the plasma membrane 2. Can move within the bilayer 3. Hydrophobic interactions hold membrane together Membranes are semifluid 3. Fluidity- individual molecules remain in close association yet have the ability to readily move within the membrane 4. Semifluid- most lipids can rotate freely around their long axes and move laterally within the membrane leaflet 5. “Flipflop” of lipids from one leaflet to
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the opposite leaflet does not occur spontaneously 4. Flippase requires ATP to transport lipids from one leaflet to another The Fluidity of Membranes 6. The fluidity of a membrane depends on its composition 5. Temperature 6. Fatty acid saturation 7. Cholesterol content The Fluidity of Membranes 7. The type of hydrocarbon tails in phospholipids 8. Affects the fluidity of the plasma membrane The Fluidity of Membranes 3. The steroid cholesterol 1. Has different effects on membrane fluidity at different temperatures 1. Less fluid at warmer temps (37C) 2. Prevents close packing of phospholipids at lower temps Membrane Proteins and Their Functions 1. The biological membrane 2. Is a collage of different proteins and carbohydrates embedded in the fluid matrix of the lipid bilayer 3. The “tiles”of the fluid mosaic 4. Relative amounts vary Proteins bound to membranes o Integral membrane proteins o Peripheral membrane proteins Membrane Proteins and Their Functions Figure 2. Integral proteins 3. Penetrate the hydrophobic core of the lipid bilayer
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This note was uploaded on 06/12/2011 for the course BIO 183 taught by Professor Parks during the Spring '07 term at N.C. State.

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Chapter 5 - Brooker CH 5 Membrane Structure and Transport...

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