Exam 2 - Practice questions Flashcards
________________ is a class of steroids that regulate calcium ion metabolism
A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin K
B. Vitamin D
The “reversal potential” of a passive ion channel is the membrane potential at which there is no overall
transport through the channel. The ClC chloride channel is a passive ion transporter. The extracellular
chloride concentration is usually about 5 times higher than the inside of the cell, but the cell also has a
membrane potential that is usually negative inside. At 37 oC, the reversal potential of chloride ions is:
A. +136 mV
B. -136 mV
C. -43 mV
D. -5 mV
C. -43 mV
The structure of hen egg white protein has been solved and the torsion angles and are shown for
each residue in the table below. What structure motif most likely forms as a result of this protein
sequence?
A. β strand connected to another β strand with a break (or loop/turn) in between
B. α Helix connect to another α Helix with a break (or loop/turn) in between
C. β strand connected to another β strand with a alpha helix in between
D. α Helix connected to a β strand with a break (or loop/turn) in between
E. None of the above are correct.
D. α Helix connected to a β strand with a break (or
O2 binding to hemoglobin (Hb) is shown in the lower curve in the following figure. Arterial PO2 is
typically 100 mm Hg and venous PO2 is 30 mm Hg, which is also the typical PO2 in tissues that
consume oxygen. How many O2 molecule(s) would each Hb typically unload when atrial blood delivers
oxygen to oxygen-consuming tissues?
A. Less than 1
B. 1
C. 2
D. 4
C. 2
Because of the Bohr effect, the oxygen loading of hemoglobin is sensitive to blood CO2 concentrations.
The Bohr effect is due to the conformational rearrangement of a number of amino acid residues in the
interface between the and subunits of hemoglobin during the TR transition. These residues whose
conformational changes give rise to the Bohr effect include:
A. Cys, Ser, Thr
B. Val, Gly, Tyr, Ala
C. Gln, Asn, Ser, Val
D. His, Arg, Asp, Lys
D. His, Arg, Asp, Lys
Which of the following best explains the difference in the membrane diffusion rates observed in the two
experiments?
A. The membrane compositions of mouse and human cells are expected to be very different and the
diffusion rate in the fused membrane in Expt A is expected to be different from the intrinsic
diffusion observed for human cells in Expt B.
B. The fluorescent probes in Expt B must have modified the phospholipid molecules significantly
enough to affect their diffusion rate.
C. The antibodies in Expt A are bound to proteins whereas the probes in Expt B are bound directly to
the headgroup of phospholids, and membrane proteins often diffuse slower than lipid molecules.
D. Upon membrane fusion, the fluidity of the membrane is temporarily decreased because SNARE
proteins are deployed to effect membrane fusion.
C. The antibodies in Expt A are bound to proteins whereas the probes in Expt B are bound directly to
the headgroup of phospholids, and membrane proteins often diffuse slower than lipid molecules.
Which of the following changes in the experiment would affect the observed diffusion rate in Expt B?
A. lowering the temperature B. the addition of cholesterol molecules C. replacing the reintroduced phospholipid molecules by ones with higher degree of unsaturation on their fatty acid tails D. All of the above
D. All of the above
Mouse and human cell membranes have different concentrations of sphingolipids and cholesterols.
Which of the following membrane constituents would you expect to be different between the
membranes of these two species?
A. the concentration of membrane-associated proteins on the cytoplasmic side
B. the stability of GPI-linked proteins on the cell surface
C. the degree of glycosylation of membrane-bound proteins
D. the formation of lipid rafts
D. the formation of lipid rafts
In addition to a cell membrane, bacteria often have cell walls that are made up of _________________.
A. aminoglycans
B. proteoglycans
C. glycoproteins
D. peptidoglycans
D. peptidoglycans
Which of the following explains why the ferrous ion is not oxidized to the ferric state in the globin
proteins even though free heme in solution is readily oxidized?
A. when bound to globins, the heme is always planar; when free in solution, heme adopts a nonplanar
configuration which allows the oxidation of the iron
B. the globin proteins provide a hydrophobic environment that prevents oxidation
C. coordination with the proximal histidine allows any oxidized iron to be rapidly reduced back to the
ferrous state
D. since the oxygen is hydrogen bound to the distal histidine, if oxidation of iron does occur, the distal
histidine allows for rapid reduction
B. the globin proteins provide a hydrophobic environment that prevents oxidation
Which type of molecule is LEAST likely to be found in a eukaryotic cell membrane?
A. Phospholipid
B. Cholesterol
C. Glycoprotein
D. Peptidoglycan
D. Peptidoglycan
The functioning of all of the following proteins involve the hydrolysis of ATP, EXCEPT
A. aquaporin B. the calcium transporter Ca2+ -ATPase C. MDR (multi-drug resistant) proteins D. myosin
A. aquaporin
When comparing the sequences of a peripheral membrane protein with an integral membrane protein,
which of the following amino acids would most likely be present in a higher percentage in the integral
membrane protein?
A. Asp
B. Leu
C. His
D. Ser
B. Leu
