Question

What does high AND low cooperativity mean in terms of the change in partial pressure and oxygen saturation?

Answer 1

Cooperativity means, the increase or decrease in the rate of interaction between a reactant and a protein as the reactant concentration increases.

Partial pressure according to the given question means, partial pressure is of two ways i.e, partial pressure exerted by oxygen in lungs due to its high concentration, and where as partial pressure exerted by carbondioxide released during the metabolic activites of the cells in the body and it is said to be partial pressure of Co_2.

Oxygen saturation means percentage of haemoglobin bonded with O₂  in the body, it may be 90% in nromal individuals.

Haemoglobin(Hb) consists of 2 alpha chains and 2 beta chains of protein called globin and a prosthetic group of heme(iron). each molecule of Hb contains 4 molecules of heme and each molecule of heme binds with 1 O₂, hence 1 molecule of Hb binds with 4 molecules of O₂. The combination of O₂ and Hb is loose and reversible. The O₂ is takenup readily by Hb at high partial pressures of O₂ i.e.,at high O₂ concentrations in lungs and is released at low concentrations of O₂ and high concentrations of Co₂ i.e,at partial pressures of Co₂ in the tissues of the body, Thus providing an effective system for transport of oxygen from the atmosphere to the cells of the body.

Fel No = 0. с дэс Polypeptide chain Polypeptide chain DEOXYGENATED HAEMOGLOBIN OXYGENATED HAEMOGLOBIN

At O₂ tensions of 100mmHg or more, Hb is virtually 100% saturated and approximately 1.34 ml of O₂ is combined with each gram of Hb.

Deoxy haemoglobin (hemoglobin not attached to O₂) can loosely combine with O₂ forming OXY-Hb, where oxygen binds to Fe ( iron) in the heme group at high concentrations, exerting high partial pressures and Co₂ will be in low concentrations with low partial pressure. OXY-Hb releases oxygen in tissues where there is low concentrations of oxygen and Hb here combines with Co_2, where it is in high concentrations thus exerting high partial pressure. Co₂ binds to Hb with its globin (protein) molecules at their NH₂ groups and thus forming carbaminohaemoglobin.

100 95.8 ----- %) Percent saturation (50 26.8 80 40 120 Oxygen partial pressure (pO,, mmHg)