BRS PHYSIOLOGY: CELL PHYSIOLOGY EXAM QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED BY EXPERTS
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BRS PHYSIOLOGY
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BRS PHYSIOLOGY
BRS PHYSIOLOGY: CELL PHYSIOLOGY EXAM QUESTIONS AND ANSWERS WITH COMPLETE SOLUTIONS VERIFIED BY EXPERTS
Which of the following characteristics is shared by simple and facilitated diffusion of glucose?
(A) Occurs down an electrochemical gradient
(B) Is saturable
(C) Requires metabolic energy
...
BRS PHYSIOLOGY: CELL PHYSIOLOGY EXAM QUESTIONS AND
ANSWERS WITH COMPLETE SOLUTIONS VERIFIED BY EXPERTS
Which of the following characteristics is shared by simple and facilitated
diffusion of glucose?
(A) Occurs down an electrochemical gradient
(B) Is saturable
(C) Requires metabolic energy
(D) Is inhibited by the presence of galactose
(E) Requires a Na+ gradient
The answer is A.
Both types of transport occur down an electrochemical gradient (“downhill”) and do not
require metabolic energy. Saturability and inhibition by other sugars are characteristic
only of carrier- mediated glucose transport; thus, facilitated diffusion is saturable and
inhibited by galactose, whereas simple diffusion is not.
During the upstroke of the nerve action potential
(A) there is net outward current and the cell interior becomes more negative
(B) there is net outward current and the cell interior becomes less negative
(C) there is net inward current and the cell interior becomes more negative
(D) there is net inward current and the cell interior becomes less negative
The answer is D.
,During the upstroke of the action potential, the cell depolarizes or becomes less
negative. The depolarization is caused by inward current, which is, by definition, the
movement of positive charge into the cell. In nerve and in most types of muscle, this
inward current is carried by Na+.
Solutions A and B are separated by a semipermeable membrane that is
permeable to K+ but not to Cl−. Solution A is 100 mM KCl, and solution B is 1 mM
KCl. Which of the following statements about solution A and solution B is true?
(A) K+ ions will diffuse from solution A to solution B until the [K+] of both
solutions is 50.5 mM
(B) K+ ions will diffuse from solution B to solution A until the [K+] of both
solutions is 50.5 mM
(C) KCl will diffuse from solution A to solution B until the [KCl] of both solutions
is 50.5 mM
(D) K+ will diffuse from solution A to solution B until a membrane potential
develops with solution A negative with respect to solution B
(E) K+ will diffuse from solution A to solution B until a membrane potential
develops with solution A positive with respect to solution B
The answer is D.
Because the membrane is permeable only to K+ ions, K+ will diffuse down its
concentration gradient from solution A to solution B, leaving some Cl− ions behind in
solution A. A diffusion potential will be created, with solution A negative with respect to
solution B. Generation of a diffusion potential involves movement of only a few ions and,
therefore, does not cause a change in the concentration of the bulk solutions.
, The correct temporal sequence for events at the neuromuscular junction is
(A) action potential in the motor nerve; depolarization of the muscle end plate;
uptake of Ca2+ into the presynaptic nerve terminal
(B) uptake of Ca2+ into the presynaptic terminal; release of acetylcholine (ACh);
depolarization of the muscle end plate
(C) release of ACh; action potential in the motor nerve; action potential in the
muscle
(D) uptake of Ca2+ into the motor end plate; action potential in the motor end
plate; action potential in the muscle
(E) release of ACh; action potential in the muscle end plate; action potential in the
muscle
The answer is B.
Acetylcholine (ACh) is stored in vesicles and is released when an action potential in the
motor nerve opens Ca2+ channels in the presynaptic terminal. ACh diffuses across the
synaptic cleft and opens Na+ and K+ channels in the muscle end plate, depolarizing it
(but not producing an action potential). Depolarization of the muscle end plate causes
local currents in adjacent muscle membrane, depolarizing the membrane to threshold
and producing action potentials.
Which characteristic or component is shared by skeletal muscle and smooth
muscle?
(A) Thick and thin filaments arranged in sarcomeres
(B) Troponin
(C) Elevation of intracellular [Ca2+] for excitation–contraction coupling
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