specific integral membrane proteins mediate transport.
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_______ diffusion and _______ diffusion are two types of passive transport.
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Simple; facilitated
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The sodium-potassium pump (or Na+-K+ pump)
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results in the formation of an Na+ concentration gradient across the cell membrane.
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What advantage is gained by having so many steps in one signal transduction pathway?
answer
Greater amplification of the signal
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A student created the table above as a study guide. Evaluate the accuracy of the information shown.
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All information is accurate.
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How do carrier proteins differ from channel proteins in their role as gatekeepers of the cell?
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Carrier proteins bind to the substances they transport across the membrane via facilitated diffusion, whereas channel proteins provide a pore for substances to move across the membrane via facilitated diffusion.
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In animals, cell recognition
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involves proteins in plasma membranes.
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Some disease-causing microbes attack the body by turning on or off specific signal transduction pathways. In the disease cholera, the bacterium Vibrio cholerae causes massive diarrhea by interfering with such a pathway. A toxin from this bacterium enters intestinal cells and chemically modifies G proteins. Once modified, the G proteins can no longer cleave GTP into GDP. What would you expect to see within the intestinal cells of a person with cholera?
answer
The G proteins remain activated and continually activate adenylyl cyclase.
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A student created the table above as a study guide. Evaluate the accuracy of the information shown.
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The listed number of membrane proteins involved in primary active transport is not correct.
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Identify the processes shown in parts A and B of the figure
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A: endocytosis; B: exocytosis
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A species of fish spends part of its life cycle under conditions of moderate temperatures and part of its life cycle under extremely cold conditions. What change in the cell membranes of this fish might be expected to occur as conditions shift from moderate to extremely cold temperatures?
answer
The fish's cells would slow production of cholesterol and increase production of unsaturated, short chain fatty acids.
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Each substance, A, B, and C, is transported across the cell membrane via passive transport. Identify the substances corresponding to their specific type of transport checked in the table.
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A: K+; B: O2; C: galactose
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If a suspension of red blood cells in an isotonic NaCl solution was suddenly diluted with pure water by a factor of 10, the cells would
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swell and lyse (burst).
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Receptor-mediated endocytosis
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results in the formation of clathrin-coated vesicles.
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Both primary and secondary active transport require energy in the form of _______ to drive substances across a cell membrane
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ATP
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The phosphorylation of proteins by ATP
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is catalyzed by enzymes known as "protein kinases."
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Adenylyl cyclase
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makes cAMP from ATP with the liberation of pyrophosphate (PPi).
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Evaluate the accuracy of the information summarized in the flowchart. Does it accurately show the steps involved in a G protein-linked signal transduction pathway?
answer
The receptor protein does not undergo self-phosphorylation.
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How are temperature and fluidity of the cell membrane related?
answer
Across a broad temperature range, fluidity of the cell membrane decreases as temperature decreases.
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In addition to the lipid bilayer and proteins, membranes may contain _______ in the form of _______ and _______.
answer
carbohydrates; glycoproteins; glycolipids
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Suppose the concentration of epinephrine in the bloodstream of an animal drops. The cyclic AMP concentration in liver cells would be expected to _______ because _______ activity would _______.
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decrease; adenylyl cyclase; decrease
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A key property of signal transduction pathways is that one signal molecule binding to a receptor protein in the cell membrane
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can result in several thousand events at the end of the pathway.
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Osmosis is
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the movement of water across selectively permeable membranes.
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Three substances need to be maintained inside a cell at the concentrations shown in column 2 of the table above. Which substance(s) are most likely to be moved across the membrane by passive transport if the typical external concentrations are those shown in column 3?
answer
X only
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How do primary and secondary active transport mechanisms differ?
answer
The goal of primary active transport is to move ions across the cell membrane against their concentration gradients; the goal of secondary active transport is to establish these same gradients to drive transport of another substance.
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