Anatomy and Physiology Answer Key

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Unformatted text preview: to the cells and tissues (which are dehydrated and therefore have a more negative water potential than the drink). Note: Many sports drinks are isotonic. Depending on the level of dehydration involved, these drinks are more effective when diluted. 7. (a) Water will move into the cells and they will burst (lyse). (b) The cells would lose water and the plasma membrane would crinkle up (crenulate). (c) Water will move into the cells and they will burst (lyse). 8. Malarial parasite: Isotonic to blood. Ion Pumps (page 27) 1. ATP (directly or indirectly) supplies the energy to move substances against their concentration gradient. 2. (a) Cotransport describes coupling the movement of a molecule (such as sucrose or glucose) against its concentration gradient to the diffusion of an ion (e.g. H+ or Na+) down its concentration gradient. Note: An energy requiring ion exchange pump is used to establish this concentration gradient. (b) In the gut, a gradient in sodium ions is used to drive the transport of glucose across the epithelium. A Na+/K+ pump (requiring ATP) establishes an unequal concentration of Na+ across the membrane. A specific membrane protein then couples the return of Na+ down its concentration gradient to the transport of glucose (at a rate that is higher than could occur by diffusion alone). (c) The glucose then diffuses from the epithelial cells of the gut into the blood stream, where it is transported away. This maintains a low level in the intestinal epithelial cells. 3. Extracellular accumulation of Na+ (any two of): – maintains the gradient that is used to cotransport useful molecules, such as glucose, into cells. – maintains cell volume by creating an osmotic gradient that drives the absorption of water – establishes and maintains resting potential in nerve and muscle cells – provides the driving force for several facilitated membrane transport proteins (k) Name: Cytoskeleton Location: Throughout cytoplasm Function: Provides structure and shape to a cell, responsible for cell movement (e.g. during muscle contraction), and provides intracellular transport of organelles and other structures. Visible under LM: No Passive Transport Processes (page 25) 1. (a) Large surface area (b) Thin membrane 2. (a) and (b) any of: – Molecules always move down a concentration gradient (from high to low c...
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This document was uploaded on 01/28/2014.

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