What Is 2 3 Bpg

Question

The oxygen dissociation curve for haemoglobin (Hb) in the absence and presence of 2,3-BPG is shown in (i) below: Bohr Effect and 2,3-BPG on Hb It can seen that the curve has shifted to the right (MC-one incorrect) and the oxygen affinity is manifestly decreased, as it takes a higher concentration (pressure level) of oxygen to achieve the aforementioned percentage saturation (MC-2 correct — and and then is pick MC-4 every bit far as I and @JM97 can see, agreeing with the poster. MCQs are an educational anathema!).

The physiological significance of this is considered in detail in my respond to another question, but, in short, it ensures that an adequate proportion of the (smaller) amount oxygen taken upwardly at the lower pressure in the lungs is released in the tissues (3 minus 4, cf. 1ʹ minus 2).

To address the interaction betwixt the effect of two,3-BPG and the Bohr Event one needs to consider the corresponding curves for the event of hydrogen ions (falling pH), shown in (2), higher up (meet also my detailed answer to this question). It tin be seen that the outcome of hydrogen ions is similar to that of 2,3-BPG. Tin can these 2 have independent (condiment) effects? It is known from molecular studies that they both interact with and stabilize deoxy-haemoglobin at different positions (come across ii, below), and in ane model of the allosteric machinery they tin can be considered every bit shifting the equilibrium from the tense (deoxy-) to the relaxed (oxy-) state of haemoglobin: Tense and relaxed states of Hb (i) Generalized diagram of allosteric equilibrium of tetrameric protein betwixt relaxed country (where it tin bind substrate/ligand) and tense state. Negative effectors favour the tense state. (two) Illustration of this for haemoglobin, where H⁺ ions protonate His-146 of the β-subunits and 2,3-BPG forms ionic bridges between the 2 β-subunits.

And then it would announced that Bohr effect can still augment the 2,3-BPG upshot, just I would imagine that the extent of this augmentation would depend on the initial position of equilibrium, and I would not expect information technology to be condiment — I may be incorrect. (Is MC-3 correct or not? A school pupil tin inappreciably be expected to know unless he had been fed the 'correct' answer. Perhaps he is intended to translate the option equally significant "does the 2,3-BPG issue work in the opposite management to the Bohr effect". Yous may now understand why I loath MCQs.)

Bibliography

The diagrams are my own, based on various sources I have used over the years. To cheque whether what I have written is correct, the reader may wish to check whatsoever of the many accounts online, including the post-obit which have references to original material: