15. Facilitated diffusion differs from active transport in thatA. faci

15. Facilitated diffusion differs from active transport in thatA. facilitated diffusion transports against a concentration gradient while active transport does notB. facilitated diffusion requires expenditure of energy while active transport does notC. active transport requires expenditure of energy while facilitated diffusion does notD. facilitated diffusion involves carrier proteins while active transport does notE. facilitated diffusion works against a concentration gradient while active transport works only with the concentration gradient16. Amino acids are carried to the ribosome attached to molecules calledA. initiation factorsB. anticodonsC. mRNAD. tRNA17. When two chambers are separated by a membrane permeable to water but not solute, if water is free to move in either direction without limitation or pressure, then water willA. move until the concentration of solute on both sides of the chamber is equalB. move until there is no water on the dilute sideC. move until there is no water on the concentrated sideD. move until the concentration of water on both sides of the chamber is equal18. The two components of extracellular fluid, the interstitial fluid and the blood plasma, areA. completely continuousB. separated by the cell wallsC. within the cells of the bodyD. separated by the capillary walls19. An aqueous solution has an osmolarity of 318 mOsm. If a cell with an intracellular osmolarity of 260 mOsm is placed into this solution, the solution is said to beA. hypertonicB. isotonicC. isoosmoticD. hypotonic20. The reason ions such as Na+, K+, and Ca2+ diffuse across plasma membranes more rapidly than would be expected across a lipid membrane is thatA. their negative charge causes them to dissolve in the polar lipids in the membraneB. ions diffuse through polar lipids more readily than non-charged particles doC. their positive charge causes them to dissolve in the polar lipids in the membraneD. there are proteins that form channels through which these ions can more readily pass 21. Which of these ions is actively transported through the cell membrane to re-establish a resting potential?A. K and Mg B. Na and K C. Mg and Cl D. Ca and Cl22. In what way does the interior surface of the cell membrane of a resting (non-conducting) neuron differ from the external environment? The interior is: A. positively charged and contains less sodium. B. negatively charged and contains less sodium. C. negatively charged and contains less potassium D. positively charged and contains more sodium. 23. Which of the following is true about the movement of ions across excitable living membranes? A. Ions can move passively across membranes through leakage channels. B. Some ions are prevented from moving down their concentration gradient by ATP-driven pumps. C. Ion gates in the membrane can open in response to electrical potential changes. D. All of these are correct.24. Propagation of action potential and transmission mean: A. current flow along the cell membrane B. current flow through the synapse C. current flow using saltatory conduction D. all of the above25. According to the sliding filament mechanism of skeletal muscle contraction, during contraction:A. The thick filaments stay the same size but the thin filaments shorten.B. The thin filaments stay the same size but the thick filaments shorten.C. Both thick and thin filaments shorten.D. The sarcomeres shorten.Extra! (5 pts).1. Which of the following is an important function of ATP in skeletal muscle?It is required for the dissociation of myosin from actin.It is hydrolyzed by the ATPase that pumps calcium ions into the sarcoplasmic reticulum.It is used for the phosphorylation of myosin.It is required for the attachment of myosin to actinA and B.2. At the neuromuscular junction, A. the release of acetylcholine from the motor neuron in the motor end plate occurs. B. acetylcholinesterase inhibits repolarization of the motor end – plate. C. It is used for the phosphorylation of myosin. D. It is required for the attachment of myosin to actin E. A and B.3. Which of the following statements regarding the action of curare at the neuromuscular junction is true? A. Curare is an epinephrine agonist. B. Curare is an acetylcholine agonist C. Curare inhibits acetylcholinesterase. D. Curare binds to acetylcholine receptors4. Which of the following descriptions of skeletal muscle contraction is correct? A. Skeletal muscle contraction requires the influx of extracellular Ca2+ B. Skeletal muscle contraction involves interactions between thick and thin filaments C. Skeletal muscle contraction results from cross-bridge cycling, D. The site of calcium regulation of skeletal muscle contraction is on the thin filament E. All of the above5. Explain briefly why action potential of cardiac muscle is significantly longer than skeletal muscle.

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