The crocodile which can remain underwater without breathing for up to an hour, drowns it air-breathing prey and then dines on them at its leisure. An adaptation that aids the crocodile in doing so is that it can utilize virtually 100% of the O2 in its blood whereas humans, for example, can extract only -65% of the O2 in their blood. (a) Draw an O2 binding curve comparing crocodile hemoglobin to that of normal hemoglobin. humne ih (b) Experiments have demonstrated that 2,3 bis-phosphoglycerate has no effect on the O2 binding of crocodile hemoglobin. However, it has been shown that 2 molecules of bicarbonate bind to deoxyhemoglobin tetramers but not to oxyhemoglobin tetramers of crocodile hemoglobin. Describe how bicarbonate might effect the O2 affinity of crocodile hemoglobin. Make sure to detail what regions of the hemoglobin tetramek might be bound by bicarbonate and how this would influence structural changes in the crocodile hemoglobin that would, in turn, affect O2 affinity. (c) Sketch the biochemical reactions in red blood cells that result in bicarbonate formation in venous blood. Write balanced equations and identify any enzymes that might be involved. If an enzyme is required, indicate which reaction is enzyme-catalyzed.

Answer is explained in the explanation section below.

Explanation:

Note: Please refer to the attachment for the O2 binding curve comparing crocodile hemoglobin to that of normal hemoglobin.

so as we know that crocodile can remain under water without breathing for an hour using certain important factor it includes the process :

 Hb(4O2) :↔: (4O2) + deoxyHB → deoxyHB-CO3 -

At the tissues, there is an equilibrium between oxygenated and deoxygenated Hb, depending upon the oxygen concentration in the tissues. Utilization of oxygen by the crocodile tissues will remove the oxygen from the right of the first equilibrium expression, causing the dissociation of oxygen from oxyhemoglobin.

At the same time, the crocodile tissues are generating carbon dioxide from metabolism. This binds to deoxyHb, generating the carboxylated form. This reaction depletes the deoxyHb from the center of the above equilibrium, causing further incentive for oxyHb to give away its oxygen.

When the crocodile has its prey underwater and is using lots of energy to keep its jaws clamped on the prey, O2 is consumed and CO2 is produced. CO2 is converted to protons and bicarbonate ions as follows: CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3 - H+ is an allosteric inhibitor that specifically binds the deoxy or T state of hemoglobin, shifting the equilibrium from the R state to the T state. This is the pH Bohr Effect.

In addition, the problem states that HCO3 - also specifically binds the deoxy or T state of crocodile hemoglobin. The shift to the deoxy or T state by H+ and HCO3 - lowers Hb affinity for O2, allowing for nearly complete O2 unloading and utilization in the crocodile’s blood .