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MMSC 490 Exam 3 Questions And Accurate Answers
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MMSC 490 Exam 3 Questions And Accurate Answers2024-2025
What is the primary reason mammalian red blood cells are used for studies of the
plasma membrane?
a. They are abundant and comparatively easy to obtain.
b. They have larger plasma membranes than all other cell types.
c. They are of particular interest because they are composed of a lipid monolayer.
d. They lack nuclei and membrane-bounded organelles. Answer d. They lack nuclei and
membrane-bounded organelles.
Two examples of membrane lipids that are present in small amounts are
a. cholesterol and phosphatidylcholine.
b. glycolipids and phosphatidylinositol.
c. phosphatidylcholine and sphingomyelin.
d. phosphatidylethanolamine and phosphatidylserine. - Answer b. glycolipids and
phosphatidylinositol.
Which of the following lipids are distinctly enriched in lipid rafts?
a. Cholesterol and sphingolipids
b. Glycolipids and phosphatidylinositol
c. Phosphatidylcholine and sphingomyelin
d. Phosphatidylethanolamine and phosphatidylserine - Answer a. Cholesterol and
sphingolipids
,Which of the following will not solubilize a typical peripheral membrane protein?
a. Detergent
b. Extreme pH
c. High salt concentration
d. Mildly hypertonic saline Answer d. Mildly hypertonic saline
A feature common to most transmembrane proteins is
a. a phosphorylated exterior domain.
b. an α-helical region of about 20 to 25 hydrophobic amino acids.
c. an amino acid sequence rich in acidic residues.
d. a structure consisting almost exclusively of β-sheets. Answer b. an α-helical region of
about 20 to 25 hydrophobic amino acids.
Membrane proteins are able to move
a. from the inner to the outer surface of a membrane.
b. laterally within the plane of a membrane.
c. from apical to basal surfaces of intestinal epithelial cells.
d. only if attached to microtubules or microfilaments. - Answer b. laterally within the
plane of a membrane.
Which of the following statements about the glucose transporter is false?
a. It moves glucose across the plasma membrane by a process called "facilitated
diffusion."
b. It has 12 α-helical transmembrane segments.
,c. A change in transporter conformation is part of transport mechanism.
d. Flow through it is unidirectional. Answer d. Flow through it is unidirectional.
Which of the following statements about ion channels is true?
a. They are opened either by the binding of ligands or by changes in electric potential
across the membrane.
b. They require ATP.
c. They are open most of the time.
d. The rate of transport is slow compared to the rate of transport via carrier proteins.
-Answer a. They are opened either by the binding of ligands or by changes in electric
potential across the membrane.
Which of the following statements about the relative concentrations of Na+ and K+
inside and outside of a typical mammalian cell is TRUE?
a. The concentration of Na+ and K+ outside of the cell is about 30 times higher than
inside the cell.
b. Whereas the Na+ concentration is about 30 times greater outside the cell than inside,
K+ concentration inside the cell is 10 to 30 times greater than outside. For both ions,
however the concentration is the same, yet there is a Cl- ion concentration gradient
across the plasma membrane.
d. The inside cell concentration of Na+ is 30 times higher than outside the cell, and
inside cell concentration of K+ is 10 times higher than in the outside cell. -Answer b.
Outside cell concentration of Na+ is about 30 times higher than that inside and inside
cell concentration of K+ is 10 to 30 times higher than that outside the cell.
The resting plasma membrane potential as described by the Nernst equation is the sum
of the movement of many ions. However in practice, the movement of _______, a single
ion is the major component determining membrane potential.
a. Ca2+
, b. Cl-
c. K+
d. Na+ - Answer c. K+
Although Na+ is smaller than K+, its passage through the K+ channel is blocked by the
_______ filter.
a. CO2
b. negativity
c. positivity
d. selectivity - Answer d. selectivity
Active transport differs from facilitated diffusion in that
a. ions are not transported via active transport, only by facilitated diffusion.
b. active transport requires a protein component, whereas facilitated diffusion occurs
by simple diffusion through the plasma membrane.
c. active transport involves the transport of molecules up their concentration gradient.
d. active transport involves a conformational change in the transport molecule. - Answer
c. active transport requires the movement of molecules up their concentration gradient.
Transport of glucose into the intestinal epithelium is energized by ion gradients
established by the
a. ATP pump.
b. H+ pump.
c. Na+-K+ pump.
d. K+ channel. - Answer c. Na+-K+ pump.
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