D103ReviewPacketMidtermAns

D103ReviewPacketMidtermAns - Bio D103: Cell Biology Winter...

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Bio D103: Cell Biology Bio. Department Tutoring Winter 08: Midterm Review 2/4/08 Mon. 6:30-8:20 RH 101 Lecture 2 Biological Membranes A. Fluid Mosaic Model and the Lipid Bilayer Features Lipid bilayer with proteins inserted thoughout Found in all cells prokaryotic/eukaryotic Biological membranes are permeable to charged molecules Hydrophobic core Asymmetric distribution of lipids/proteins Special lipid compostion and protein composition determines an organelle Functions 1. Permeability barrier—separate inside from outside 2. Selective Permeability—only select ions/molecules can go into the cells through channels/pumps 3. Flexible—allow rapid movement and communication with environment (fluidity) Factors that lead to various Density/fluidity 1. length of hydrocarbon backbone—shorter backbone=less Van der Waals interactions with neighboring lipids more fluid 2. Concentration of Cholesterol—rigid, amphiphatic steroid, contained in both leaflets high concentration: more rigid, immobilize lipids Lower fluidity low concentration: separated lipid tails More fluidity 3. Membrane thickness: depends on TYPE of lipid Lipids Amphiphatic—hydrophilic (polar) head and hydrophobic (nonpolar) Lipids and Signaling Phosphoseriene—only on cytosilic side Gets flipped and signals macrophage for apoptosis The thickness of a membrane bylayer is 3-6 nm thick You need AT LEAST 20 non charge Amino Acids to cross membrane Exam Question Phospholipids with short or unsaturated fatty acyl chains a. decrease membrane fluidity b. increase membrane fluidity c. cause biomembranes to become thicker d. always form micelles e. allow hydrophilic molecules to diffuse across the lipid bilayer
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Memorize the hydrophobic amino acids Be able to determine if given amino acid can be in a transmembrane domain *Find which a.a. compose an alpha helix Groups within the 20 Amino Acids Hydrophobic: Common in TM domain Polar but uncharged: Can be found in TM Hydrophilic: NOT/NEVER in TM domain Leu, Ile, Val, Ala, Gly, Met, Pro, Trp, Phe, Cys Ser, Thr, Asn, Gln, Tyr Acidic: Asp, Glu Basic: Lys, Arg, His Glycosylation Blood groups --glycans on cell surface of blood cells change sugars on surface with enzymes Antigens— anti-body generator recognized by antibody Glycans on red blood cells are different Genetically determine the addition of sugars The opposite antibody is always found in the serum How are blood groups determined? Antibodies react with antigens found on blood cell surface 2
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Lecture 3. – How to get across a membrane I. Protein mediated transport across a membrane A. Fall into 3 major categories 1. Carriers/Transporters a. Conformational change b. Saturable transport c. Selectivity achieved by binding site for solute 2. Channels a. Not as selective as carriers (only distinguish solutes by size and charge) b. Only transport down electrochemical gradient (passive transport) 3. Pumps a. Often powered by ATP or light B. Carriers/Transporters
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D103ReviewPacketMidtermAns - Bio D103: Cell Biology Winter...

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