BCCB2000 Lecture 6 Questions Flashcards
(24 cards)
Which of the following is not correct concerning 2,3-bisphosphoglycerate (BPG)? A. It increases the affinity of hemoglobin for oxygen. B. It binds at a distance from the heme groups of hemoglobin. C. It is normally found associated with the hemoglobin molecules that are extracted from red blood cells. D. It is an allosteric modulator. E. It binds with lower affinity to fetal hemoglobin than to adult hemoglobin.
A. It increases the affinity of hemoglobin for oxygen.
Cooperative binding of oxygen by hemoglobin: A. is induced by hemoglobin. B. is a result of different affinities for oxygen by each subunit protein. C. is induced by oxygenation. D. is a result of interaction with myoglobin.
C. is induced by oxygenation.
An allosteric interaction between a ligand and a protein is one in which: A. two different ligands can bind to the same binding site. B. the binding of the ligand to the protein is covalent C. multiple molecules of the same ligand can bind to the same binding site D. the binding of a molecule to a binding site affects the binding of an additional molecule to the same site E. the binding of a molecule to a binding site affects the binding properties of another site on the protein
E. the binding of a molecule to a binding site affects the binding properties of another site on the protein
Haemoglobin is: A. a tetramer of 4 myoglobin proteins. B. a tetramer of four globin chains and one heme prosthetic group. C. a dimer of subunits each with two distinct protein chains (alpha and beta). D. a dimer of subunits each with two myoglobin proteins. E. an erythrocyte.
C. a dimer of subunits each with two distinct protein chains (alpha and beta).
A hyperbolic binding curve differs from a sigmoidal binding curve in that the hyperbolic curve: A. has a single equilibrium constant for oxygen binding. B. binds more oxygen after the initial proteins first bind oxygen. C. shows cooperativity. D. binds up to four molecules of oxygen. E. All of the above
A. has a single equilibrium constant for oxygen binding.
The role of the proximal histidine in myoglobin is to: A. prevent tight CO binding B. bind to the fifth coordination position of Fe2+ C. bind H2O D. bind O2 E. prevent tight CO2 binding
B. bind to the fifth coordination position of Fe2+
Haemoglobin has the following roles in vertebrates: A. transports oxygen B. transports CO2 C. transports H+ D. acts as a buffer E. all of the above
E. all of the above
Which statement is false about the heme group? A. When oxygen binds to heme, the iron ion is oxidized from Fe2+ to Fe3+. B. If exposed to air, a free heme group (not associated with hemoglobin) is readily oxidized converting Fe2+ to Fe3+ and can no longer bind oxygen. C. The heme group is tightly, but non-covalently, held in myoglobin molecule. D. The chemical structure of the heme groups in myoglobin and hemoglobin are identical
A. When oxygen binds to heme, the iron ion is oxidized from Fe2+ to Fe3+.
Cooperative binding and allosterism of hemoglobin allow oxygen to be unloaded at low partial pressures of oxygen in the tissues. True or False?
True
The role of the distal histidine in myoglobin is to: A. bind O2 B. prevent tight CO binding C. enhance CO2binding D. bind H2O E. prevent tight CO2 binding
B. prevent tight CO binding
The amino acid substitution of Val for Glu in Haemoglobin S results in aggregation of the protein because of ___________ interactions between molecules.
hydrophobic
The main property of myoglobin and hemoglobin that makes them an efficient system for oxygen delivery from lungs to muscles is: A. hydrophobicity. B. different binding affinities for oxygen. C. movement of the protein shapes. D. cooperativity. E. All of the above
B. different binding affinities for oxygen.
The hydrophobic crevice of globin prevents complete electron transfer to the oxygen so that the electron returns to the iron atom when oxygen dissociates. True or False?
True
The quaternary structure of haemoglobin changes from the T state to the R state ________. A. only after four molecules of oxygen are bound B. after the binding of one molecule of oxygen causes a change in the primary structure C. when haemoglobin is completely deoxygenated D. when at least one subunit on each dimeric unit (αβ dimer) is oxygenated
D. when at least one subunit on each dimeric unit (αβ dimer) is oxygenated
Which of the following conditions is likely to result in a ‘left-shift’ of the oxygen saturation curve in haemoglobin? A. increased concentration of carbon dioxide B. increased concentration of carbon monoxide C. increased concentration of protons D. increased concentration of 2,3 BPG
B. increased concentration of carbon monoxide
At high carbon dioxide concentrations the carbamates of hemoglobin can be formed. The carbamates of oxyhemoglobin are less stable than those of deoxyhemoglobin. True or False?
True
Myoglobin and the subunits of haemoglobin have: A. very similar primary and tertiary structures. B. very similar primary structures, but different tertiary structures. C. very similar tertiary structures, but different primary structures. D. very different primary and tertiary structures. E. no obvious structural relationship.
C. very similar tertiary structures, but different primary structures.
The porphyrin prosthetic group is held into the interior of globin molecules by covalent bonds to specific amino acid residues. True or False?
False
Myoglobin has a greater affinity for oxygen than haemoglobin. True or False?
True
The Bohr effect describes the effect of pH on hemoglobinʹs ability to bind oxygen. Oxygen binds more tightly at low pH and less tightly at higher pH values. True or False?
False
The amino acid substitution of Val for Glu in Hemoglobin S results in aggregation of the protein because of ___________ interactions between molecules.
hydrophobic
Conditions in the tissues which enhance the delivery of oxygen by haemoglobin are the presence of: A. carbon dioxide. B. 2,3 BPG. C. protons. D. A, B, & C above E. A and B above
D. A, B, & C above
Myoglobin and the subunits of haemoglobin have: A. very similar primary and tertiary structures. B. very similar primary structures, but different tertiary structures. C. very similar tertiary structures, but different primary structures. D. very different primary and tertiary structures. E. no obvious structural relationship.
C. very similar tertiary structures, but different primary structures.
Conditions in the tissues which enhance the delivery of oxygen by haemoglobin are the presence of: A. carbon dioxide. B. 2,3 BPG. C. protons. D. A, B, & C above E. A and B above
D. A, B, & C above
