Question

Question 3

In humans, the urge to exhale results from the high concentration of CO2 in the blood. Divers often hyperventilate (rapid breathing for several minutes) prior to making a dive in the belief that this will increase the O2 content in their blood. Use your knowledge of haemoglobin function to evaluate whether this practice is useful.

Question 4

Glutathione is a tripeptide, ECG. It contains an unusual peptide linkage between the amine group of cysteine and the carboxyl group of the glutamate side chain. It is an antioxidant and helps protect cells from reactive oxygen species such as free radicals and peroxides.

a) Draw the structure of the tripeptide and estimate its isoelectric point (pI).

b) The Cys moiety can be readily oxidized to form disulphide bonds. It is crucial that this tripeptide is maintained in the reduced form else it will lose its ability to transport oxygen effectively. Why do you think this is so?

Question 5

One molecule of 2,3-bisphosphoglycerate (BPG) binds to one molecule of haemoglobin (Hb) in a central cavity of the haemoglobin molecule. Is the interaction between BPG and Hb stronger or weaker than it would be if BPG were bound to the surface of the protein instead? Explain your answer.

Answer 1

For question 3 you have to know how hemoglobin and erythrocyte work. Co2 is transported in three ways, 20% as carbaaminohemoglobin, 75% transports as HCO3 and only 5% as dissolved CO2.
Now, when hyperventilating, the available concentration of HCO3 increases, this acidifies the medium, the hemoglobin increases its affinity for oxygen due to the lower pH (Bhor effect occurs). That is why it is useful hyperventilate to have an extra reserve of oxygen within the hemoglobin

For question 4

a)

b) It may be because reacting with other SH groups in hemoglobin changes the conformation of this and lowers the specificity for oxygen and with this its main function.

For question 5:

There is something known as via Rapaqport-Lwebering (a little metabolic pathway)
While this route is done the erythrocyte stops winning 2 ATP by glycolysis
In this the 2,3 bisphosphoglyceraldehyde can be inserted into the hemoglobin to make it easier to release the oxygen.
If the interaction were outside (or in the surface) it would not be very useful since the oxygen is inside the protein and it would not be necessary to have this metabolic pathway