Exam 2 Review

Exam 2 Review - Neural Communication Membrane transport...

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Neural Communication Membrane transport Permeable = if a substance can cross the membrane Impermeable = if a substance cannot pass Selectively Permeable = permits some particles to pass through while excluding others Two properties of particles that influence whether they can pass membrane without assitance: 1. the relative solubility of the particle in lipid a. uncharged or nonpolar molecules can pass i. O2, CO2, and fatty acids b. charged particles and polar molecules have low solubility i. Na+ and K+, glucose and proteins 2. the size of the particle Two general types of forces involved in transport across the membrane: 1. Passive Forces = forces that do not require the cell to expend energy to produce movement 2. Active Forces = forces requiring cell energy (ATP) expenditure to transport a substance across the membrane a. Need ATP b. Low to higher c. Against concentration gradient Diffusion = uniform spreading out of molecules due to their random intermingling Concentration Gradient = a difference in concentration between two adjacent areas Net Diffusion = difference between two opposing movements Steady State = movements of molecules from two different areas will be exactly matched going both ways. Fick’s Law of Diffusion: Used in steady state (no change) and in non-steady state (diffusion volume changes with respect to time
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1. high concentration gradient of substance ( C ), effect on rate of net diffusion goes up 2. high permeability of membrane to substance (P ), effect on rate of net diffusion goes up 3. high surface area of membrane (A ), effect on rate of net diffusion goes up 4. high molecular weight of substance (MW ), effect on rate of net diffusion goes down 5. high distance (thickness) ( ∆Χ ), effect on rate of net diffusion goes down Electrical Gradient = difference in charge between two adjacent areas that promotes the movement of ions toward the area of opposite charge. Electrochemical Gradient = the net effect of simultaneous electrical and concentration gradients on this ion. Carrier-mediated Transport Carrier – Mediated Transport = carrier proteins span the thickness of the plasma membrane and can reverse shape so that specific binding sites can alternately be exposed at either side of the membrane. - carrier “filp-flops” so that binding sited located in the interior of the carrier are alternately exposed to the ECF and ICF. - Carrier –mediated transport systems desplay three important characteristics that determine the kind and amount of material that can be transferred across the membrane: specificity, saturation, and competition . o Specificity. Each carrier protein is specialized to transport a specific substance, or at most a few closely related chemical compounds. o
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This note was uploaded on 04/30/2008 for the course BIO 242 taught by Professor Vansciver during the Spring '08 term at Rhode Island.

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Exam 2 Review - Neural Communication Membrane transport...

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