Lecture 9 - Membranes, Transport PDF

I. Membranes A. Structure, composition B. Membrane fluidity C. Membrane proteins D. Movement of things across membranes 1 Membrane proteins continued 2 Major functions of membrane proteins A. Transporters controlling what comes in and out B. Enzymes Contr...

I. Membranes A. Structure, composition B. Membrane fluidity C. Membrane proteins D. Movement of things across membranes 1 Membrane proteins continued 2 Major functions of membrane proteins A. Transporters controlling what comes in and out B. Enzymes Controlling chemical fucntions in the membrane C. Signal transduction D. Cell surface attachment/recognition 3 Two membrane protein locations A. Integral membrane proteins Trans membrane proteins B. Peripheral proteins One side or the other of the membrane 4 Typical integral membrane structure Transmembranealpha Domain helix fig 4.10 5 Transmembrane proteins can be identified based on their amino acid sequences o Stretches of non-polar amino acids indicate transmembrane domains o non-polar = hydrophobic, like the inside of the membrane bilayer 6 fig 4.11 I. Membranes A. Structure, composition B. Membrane fluidity C. Membrane proteins D. Movement of things across membranes 7 Movement across membranes (membrane transport) o Very important to be able to control who comes in and out of a cell! *KEY IDEA 8 Movement across membranes (membrane transport) o Passive transport – NO energy required happens spontanously o Active transport – energy required needs energy to move stuff o Exo/endocytosis release and absorbtion of vessicles to transport 9 Passive vs active transport 10 Passive vs. active transport some things can just diffuse PASSIVE transport ACTIVE transport burns ATP to pump out across the membrane energy required molecules NO energy required 11 Passive transport, no energy required, two types A. Passive transport – NO energy required 1)diffusion 2)facilitated diffusion B. Active transport – energy required C. Exo/endocytosis 12 Passive transport type: diffusion o things move from high to low concentration i.e. - Things move “down their concentration gradient” concentration gradient diffusion equilibrium (solvent) solutes semi-permeable things want to move from high to low concentrations membrane plasma membrane 13 Passive diffusion across semi-permeable membrane high concentration low concentration pass through based on properties and size easily they can either move across or they can't don't pass through ions don't pass through b/c the interior of the bilayer is hydrophobic 14 Passive transport type: facilitated diffusion o Passive (no energy required, driven by concentration gradients) o Membrane proteins form channels to facilitate diffusion of stuff across the membrane helps diffusion high concentration low concentration 15 Facilitated diffusion saturation 16 Facilitated diffusion – channel proteins 1)channel proteins always open, unselective, molecules constantly flow through 2)gated channel proteins 3)carrier proteins 17 Facilitated diffusion – gated channel proteins 1)channel proteins 2)gated channel proteins has a gate, closed by default, opened by signals, uses charge differentiation to open rather than burning ATP 3)carrier proteins 18 Facilitated diffusion – carrier proteins 1)channel proteins 2)gated channel proteins 3)carrier proteins carry stuff from one to the other, only binds to a specific molecule, the bonding results in change of protein structure (opens and closes at either end. Type text here 19 Movement across membranes (membrane transport) A. Passive transport – NO energy required 1)diffusion 2)facilitated diffusion B. Active transport – energy required 1)primary 2)secondary C. Exo/endocytosis 20 Active transport o Requires energy o Things move against their concentration gradient o Two types of active transport: primary – uses ATP secondary – uses electrochemical gradients 21 Active transport basic idea 22 Active transport basic idea [HIGH] P [LOW] ATP ADP P P 23 P 1˚ active transport example: sodium-potassium pump Na+ K+ 24 1˚ active transport example: sodium-potassium pump o Moves sodium ions (Na+) out of cell *Both ions are moved against their concentration o Moves potassium ions (K+) into cell gradients, so energy is needed. o The transporter uses ATP to do this Na+ ATP K+ 25 2° active transport o Does not use ATP for energy o Uses ion gradients (i.e. electrochemical) for energy o Energy released as an ion moves with its concentration gradient is used to drive movement of a solute against its concentration gradient 26 2° active transport 27 cotransport exchange diffusion Movement across membranes (membrane transport) A. Passive transport – NO energy required 1)diffusion 2)facilitated diffusion B. Active transport – energy required 1)primary 2)secondary C. Exo/endocytosis 28 Exo/endocytosis A. Exocytosis B. Endocytosis types: 1)receptor-mediated (e.g. LDL cholesterol) 2)Bulk-phase (pinocytosis) (pino = drink) 3)Phagocytosis (phago = eat) 29 Exocytosis and endocytosis 30 Endocytosis type: phagocytosis helps diffusionh 31 Summary of membrane transport types 32