Quiz 7

1. 1roof for distinct T and R hemoglobin came from experiments involving-

   1. AX-ray diffraction studies
   2. Boxygen binding experiments
   3. Cdetermination of molecular weight of hemoglobin subunits
   4. Dexperiments with carbon monoxide
2. 2The physiological increase in the blood level of BPG is an adaptation to higher elevation because

   1. AA More hemoglobin will stay in the R state
   2. BB PBG increases the affinity of hemoglobin to O2
   3. CC Hemoglobin has a reduced capacity to carry O2
   4. DD Hemoglobin's ability to bind O2 near the lungs remains virtually unchanged
   5. EA and B
   6. FC and D
3. 3In the concerted mode for cooperatively, the hemoglobin subunits --

   1. Abing or release oxygen, all at ocne
   2. Bshow maximum cooperatively when no BPG is present
   3. Cbinds to oxygen in order, first the two alpha subunits, then the two beta subunits.
   4. Dchante T to R or vice versa
4. 4The prosthetic group attached to hemoglobin is

   1. AA part of its secondary structure
   2. Ba substrate of hemoglobin
   3. Ca ligand of hemoglobin
   4. Dhydrogen bounded to hemoglobin
   5. Epermanently associated with hemoglobin
5. 5Which of the following properties is shared by both myoglobin and hemoglobin?

   1. AIf one has a point mutation from Glu to Val, they both have the ability to cause sickle cell anemia
   2. BThey are both allosteric proteins
   3. CThey both bind BPG
   4. DThey will both bind more O2 where it is more abundant, release O2 where it is more scarce
   5. EAll of the above are shared.
6. 6Myoglobin and Hemoglobin share the following properties EXCEPT

   1. AThey have both have a heme prosthetic group that binds oxygen
   2. BThey are both oxygen carrier proteins
   3. CThey are both located in blood's red cells
   4. Dtheir polypeptide structures are many alpha helices
   5. Ethey share a common evolutionary linkage
7. 7In a fetus, hemoglobin has gamma chains instead of beta chains. One difference is less positive charges in the central cavity of hemoglobin. This increase in the affinity of hemoglobin to oxygen because

   1. ABPG binds less tightly
   2. BIt allows BPG to bind more tightly
   3. CIt creates less electrostatic repulsion between the subunits of Hemoglobin
   4. DAll of the above
8. 8Which expression is the fraction of oxygen bound myoglobin in solution (theta, or Y)?

   1. A[MbO2]/[Mb][O2]
   2. B[Mb][O2]/[MbO2]
   3. C[Mb]+[MbO2]
   4. DpO2/pO2 + p50
9. 9When the dissociation constant (Kd) of any ligand is smaller by comparison, it means

   1. Athe ligand binds with lower affinity
   2. Bthe ligand binds with higher affinity
   3. Cthe concentration of the ligand has decreased
   4. Dthe concentration of the ligand has increased
10. 10The binding of one or more O2 ligands to molecule of hemoglobin will induce:

    1. Athe release of any other O2 that may have bound earlier.
    2. BA decrease in hemoglobin's ability to bind a second O2
    3. Cdissociation of the hemoglobin subunits
    4. Dthe movement of hemoglobin to an organism's muscle tissue
    5. Ean increased affinity for O2 in the remaining subunits (which have not yet bound O2)

11. 11When moving towards the lungs, hemoglobin shifts to the ___ conformation, in which the Kd for oxygen binding is _____.

    1. AR; increased
    2. BT; lowered
    3. CR; lowered
    4. DT; increased
12. 12When red blood cells migrate away from the lungs, initial oxygen dissociation from hemoglobin is stimulated by _____ and further on, dissociation is enhanced by _____.

    1. ABPG; lower [oxygen]
    2. Blower [oxygen]; lower [oxygen]
    3. CBPG; T/R transition
    4. Dlower [oxygen]; T/R transition
13. 13Which of the following is NOT correct concerning 2,3-bisphosphoglycerate (BPG)?

    1. AIt binds at a distance from the heme groups of hemoglobin.
    2. BIt binds with lower affinity to fetal hemoglobin than to adult hemoglobin
    3. CIt is an allosteric modulator
    4. DIt is normally found associated with hemoglobin extracted from red blood cells
    5. EIt increases the affinity of hemoglobin for oxygen.
14. 14The initial trigger for conformational change in hemoglobin, leading to T/R transition, involves

    1. Adramatic change in the affinity to oxygen in all four binding sites
    2. Bshift in the relative position of the alpha and beta subunits
    3. Cshift in the porphyrins plane upon oxygen binding, from concave to planar
    4. DAll of the above
15. 15The Hills coefficient

    1. Ais greater for myoglobin than it is for hemoglobin
    2. Brepresents the total number of ligand bonding sites in the proteins
    3. Cis larger when cooperatively is larger
    4. Dis the difference in fraction bound to hemoglobin between lungs and capillaries
16. 16Protection from low levels of CO poisoning is in part due to the fact that

    1. Athe binding configuration of CO to heme iron favors oxygen binding.
    2. Bthe His F8 on hemoglobin distorts the heme iron atom out of the heme plane and attracts O2, but not CO.
    3. CThe affinity of heme for O2 is much greater than for CO
    4. DThe CO cannot bind to heme in hemoglobin
    5. EAll of the above.
17. 17In the binding of oxygen to myoglobin, the relationship between the concentration of oxygen and the fraction of binding sites occupied can best be described as

    1. Ahyperbolic
    2. Bsigmoidal
    3. Clinear with positive slope
    4. Dlinear with negative slope
    5. Enonrandom
18. 18Le Chattier principle predicts that

    1. Aoxygen will dissociate from hemoglobin where blood oxygen is high
    2. Boxygen will dissociate from hemoglobin where blood oxygen is low
    3. Coxygen binding to hemoglobin is independent of blood oxygen levels
    4. Doxygen binding too hemoglobin is independent of blood oxygen levels
    5. Eoxygen will only bind to hemoglobin in R state
    6. Foxygen will only bind to hemoglobin in T state
19. 19When a ligand binds with a protein

    1. AIt is relatively non-specific
    2. BIt is usually irreversible.
    3. CIt is usually short lived
    4. DIt is usually the result of the inactivation of the proteins
    5. Eit is rare in biological systems.
20. 20The hypothesis that hemoglobin shifts between a low and a high affinity form implies that the protein-
    

    1. Ahas a prosthetic group
    2. Bhas two binding sites for oxygen
    3. Cexists in two distinct conformations
    4. Dis coded by two different genes
    5. Enone of the above
21. 21BPG binding to hemoglobin requires that:

    1. Athe protein will be in the R state
    2. BThe protein will be in the T state
    3. CThe red blood cells will be as close as possible to the lungs
    4. DThe protein will have oxygen dissociated from all its for heme groups.
    5. EThe protein can be in either R or T state.
22. 22Which of the following is the major form of hemoglobin produced in RBCs during normal adult life?

    1. Azeta2/epsilon2
    2. Balpha2/gamma2
    3. Calpha2/beta2
    4. Dalpha2/delta2
    5. Ealpha2/epsilon2
23. 23In sickle cell anemia, the gene coding for the beta-chain of hemoglobin shows

    1. Aa missense mutation leading to the formation of a shortened polypeptide
    2. Ba missense mutation leading to elimination of the heme prosthetic group, where oxygen binds
    3. Ca missense mutation leading to the substitution of glu to val
    4. DA missense mutation leading to the elimination of the central cavity of hemoglobin
24. 24When O2 binds to heme in hemoglobin, the _____ is drawn into the plane of the porphyrin, causing a conformational change that is transmitted to adjacent subunits, ________ the affinity for additional O2 binding.
    Select one:

    1. AHistidine E7; lowering
    2. BFe2 atom; decreasing
    3. CHistidine E7; increasing
    4. DFe2 atom; increasing
25. 25In myoglobin's binding surge, the dissociation constant Kd is

    1. A[Mb][O2]/[MbO2]
    2. BpO2/pO2+p50
    3. C[Mb]+[MbO2]
    4. D[MbO2]/[Mb][O2]

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Quiz sobre Quiz 7, criado por genny stubbs em 14-06-2017.

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genny stubbs

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Criado em 14 jun 2017 · atualizado em 14 jun 2017

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