Why do phospholipids spontaneously form bilayer structures, while oils form small droplets?
answer
Oils do not have the polar head group that phospholipids have.
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Which statement about membrane proteins is true?
answer
Peripheral membrane proteins may be associated with the phospholipid head groups.
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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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In animals, cell recognition
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involves proteins in plasma membranes.
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Which molecule would diffuse across a phospholipid bilayer fastest, if there are no proteins associated with the bilayer?
answer
NH3
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Osmosis is
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the movement of water across selectively permeable membranes.
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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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In facilitated diffusion,
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specific integral membrane proteins mediate transport.
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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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Receptor-mediated endocytosis
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results in the formation of clathrin-coated vesicles.
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Hormones are chemical signals that
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travel through circulatory systems.
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A universal feature of receptors is that they
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undergo structural (shape) changes when the signal molecule is bound.
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Which statement about receptors and enzymes is true?
answer
Both receptors and enzymes may be integral membrane proteins.
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Chemical signal transduction pathways
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involve binding of the signal molecule to receptors.
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Caffeine
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binds to a receptor in the brain.
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Adenylyl cyclase
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makes cAMP from ATP with the liberation of pyrophosphate (PPi).
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Which statement about a signal cascade is true?
answer
cAMP is referred to as a "second messenger."
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Which step of the signal transduction cascade that results in glucose release during the "fight-or-flight" response involves factors other than a nucleotide?
answer
Epinephrine binding to its receptor
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The phosphorylation of proteins by ATP
answer
is catalyzed by enzymes known as "protein kinases."
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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 _______.
answer
decrease; adenylyl cyclase; decrease
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