can you help me with 7, 8, and 9? Questions 7-9 refer to this graph 100 parñial

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can you help me with 7, 8, and 9?

Questions 7-9 refer to this graph 100 parñial pressure df axygen 7. If curve 3 represents the binding of oxygen to normal hemoglobin, which curve represents the binding of oxygen to hemoglobin at high altitudes in red blood cells with an increased concentration of BPG? )Curve 1 Curve 2 ) Curve 3 D) Curve 4 8. If curve 3 represents the binding of oxygen to normal hemoglobin, which curve represents the binding of oxygen to a mutant hemoglobin with multiple His Gly mutations in the central cavity? A) Curve1 B) Curve 2 C) Curve 3 D Curve4 9. If curve 3 represents the binding of oxygen to normal hemoglobin, which curve represents the binding of oxygen to a mutant hemoglobin with surface Tyr->Phe and His->Arg mutations that abolish tetramer formation? A) Curve 1 B) Curve 2 Curve 3 D Curve 4

Explanation / Answer

Ans. #7. 2,3-BPG binds to the beta subunit of HbA hemoglobin causes transition of R-state (HbO2) into T-state (deoxyHb) by stabilizing T-state. Stabilization of T-sate by 2,3-BPG thus triggers dissociation of O2 from HbO2.

So, in presence of higher [BPG], higher pO2 is required to attain the same % saturation at lower [BPG].

So, correct option is- D. Curve 4.

#8. The positively charged Fe2+ ion of Heme forms a coordination bond with the highly electronegative imidazole N-atom of histidine residue of the subunit. A O2 molecule, when present in blood, forms the 6th coordination bond with Fe2+ from top the plane.

So, if His is substitutes by Gly, the central Fe2+ atom of the heme bears a relatively higher positive charge. A higher positive charge on the central Fe atom would attract the highly electronegative O2 molecules more efficiently. Therefore, the mutated Hb requires less pO2 to get saturated- exhibiting a left shift.

So, correct option is- B. Curve 2

#9. Positive cooperativity (sigmoid curve) is the characteristic of tetrameric form of Hb.

Loss of tetrameric form would lead to loss of cooperativity of O2 binding, i.e. the O2 binding curve is NO MORE SIGMOID.

So, correct option is- A. Curve 1.

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