Which of the following statements surrounding Hemoglobin function is INCORRECT? In conditions of acidosis, a critical His at the \( \alpha_{1}-\beta_{2} \) interface is protonated, favouring salt bridge formation and maximizing oxygen offloading. Myoglobin shows a hyperbolic binding curve since there is only one heme subunit, preventing the subunit-to-subunit communication afforded by the heterodimeric quaternary structure of hemoglobin. 2,3-bisphosphoglycerate is a negative allosteric regulator of Hemoglobin, perventing the \( \mathrm{T} \)-to- \( \mathrm{R} \) transition required to switch conformations and alter ligand affinity. The ability of hemoglobin to switch between the \( \mathrm{R} \) and \( \mathrm{T} \) states allows the protein to maximize loading in tissues with low \( P O_{2} \), offloading in tissues with high \( P O_{2} \), and maintenance of an oxygen reserve during periods of exertion. The sigmoidal binding curve of oxygen exhibited by Hemoglobin disobeys the Law of Mass Action, since ligand binding alters the receptor and its affinity for subsequent ligand binding events.
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The question asks us to identify the incorrect statement about hemoglobin function from the given options. Hemoglobin is a protein in red blood cells that carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues back to the Show more…
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Jhankar T.
Chapter 9. Hemoglobin and Myoglobin 1. The dominant motif found in both hemoglobin and myoglobin is: a) helix-loop-helix b) twisted beta sheet c) beta barrel d) 7-TM 2. Which statement about myoglobin is not true? A) it is globular b) it contains helix-loop-helix c) it has two subunits d) it has a heme group 3. The cooperative binding behavior of hemoglobin is best explained in terms of: a) tight subunit aggregation b) active and inactive heme groups c) oxidation of the iron in heme to the +3 state d) T to R transition 4. Which statement about BPG is true? A) BPG binds to the heme groups, preventing oxygen binding b) BPG binds to the central cavity, preventing oxygen binding c) BPG binds to the heme groups, promoting oxygen binding d) BPG binds to the central cavity, promoting oxygen binding 5. CO2 reacts with water, catalyzed by the enzyme carbonic anhydrase to form the weak acid carbonic acid. This lowers the pH, thus disfavoring O2 binding with hemoglobin. However, if the solution is carefully buffered so that the pH cannot change, addition of CO2 causes a further decrease in O2 binding with hemoglobin. This may be explained in terms of: a) CO2 displaces oxygen from the heme group b) CO2 forms an N-terminal carbamate which favors the T-form c) CO2 displaces BPG which disfavors oxygen binding d) CO2 binds within a beta-barrel motif favoring the T-form 6. The proximal His binds to: a) Fe b) O2 c) CO2 d) BPG 7. The distal His binds to: a) Fe b) O2 c) CO2 d) BPG 8. In sickle-cell hemoglobin, Glu in position 6 of the beta chain is replaced by: a) Gly b) Lys c) Val d) Met 9. A person with sickle-cell trait would have about what % sickled cells? A) 100% b) 5% c) 1%
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