9 g0 Niall G. Howlett. FhD.,BCH311 . Spring 2015, Eual 43. The term positive coo

Question

9 g0 Niall G. Howlett. FhD.,BCH311 . Spring 2015, Eual 43. The term positive cooperativity is best used to descnibe the mode of action of w hich of te folo a) Collagen b) Keratin c) Myoglobin d) Glutathione c) Hemoglobin 44. The Go protein relays signals from activated transmembrane receptors to tas downstream targets. The Go protein adopts a quaternary structure consisting of four distinct subunits aPr·It is best described as a: a) heterodimer b) homodimer c) heterotetramer d) heterotrimer e) homotrimer 45. The oxygen binding curve of the hemoglobin protein is best described as: a) hyperbolic b) linear c) sigmoidal d) clectrostatic e) none of the above 46. The oxygen binding curve of the myoglobin protein is best described as: a) hyperbolic b) linear c) sigmoidal d) electrostatic e) none of the above 47. In the protein hemoglobin, H 146 of the subunit interacts with D94 of the subunit, which of the following be describes this interaction a) hydrophobic interaction/tertiary structure b) hydrophobic interaction/quaternary structure c) electrostatic interaction/secondary structure d) electrostatic interaction/tertiary structure e) electrostatic interaction/quaternary structure 48. The oxygen binding curve of the hemoglobin stripped of BPG is best described as: a) hyperbolic b) linear

Explanation / Answer

43) (e)Hemoglobin

The hemoglobin tetramer can bind 4 molecules of oxygen and because of its positive cooperativity, the fourth O2 molecule binds with 4-fold greater affinity than the first.Positive cooperativity can be explained by the sequential model but not by the concerted model.

44) (c) Heterotetramer

Homodimer-two identical subunits, ...trimer- three identical subunits,...tetramer- four identical
subunits
Heterodimer-different subunits, same for trimer and tetramer

45) (c) sigmodial curves

The shape of the oxygen dissociation curve of hemoglobin is sigmoidal (S) shaped and The oxygen dissociation curve of myoglobin is hyperbolic.

The oxygen dissociation curve of hemoglobin its shape gives Distinct oxygen binding sites are present in the molecule;oxygen is transported in the molecule from areas of high oxygen partial pressure to areas of low partial pressure.

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