Question

1) Draw and explain why the conformation freedom of peptides is limited.

2) Discuss the roles of hemoglobin and myoglobin in transporting oxygen and carbon dioxide

Answer 1

1) The conformation is limited to rotations on the bonds which leads to alpha carbon atoms and due to the rigid nature of peptide bond its restricted. The c-N bond length of peptide is 10% shorter than fond in the usual amine bonds. Because the peptide bond has a double bond character of about 40% due to its resonance. So the peptide bonds are planar. Their rigidity will reduce its freedom of polypeptide during its folding. The steric hinderance shown in the diagram between the functional groups attached to alpha atoms will be large in cis configuration. t2) Oxygen cobines with Hb to form oxyhaemoglobin and in the lungs where the partial pressure of oxygen is high, the reaction will be proceeding on the right to form oxyhaemoglobin and in tissues where the partial pressure of oxygen is low, the reaction will get reversed and Oxyhaemoglobin will release O2 forming deoxyhaemoglobin.

Role of Myoglobin in O2 and CO2 transport- Myoglobin is an iron containing protein which recieves O2 from RBC's and transports it to mitochondria where O2 gets used for cellular respiration and produces ATP. And therefore provide O2 to working muscles. They have one heme prosthetic group. It allows organisms to hold their breath for a long period of time. It has an increased affinity for O2 than Hb. Myoglobin does not bind to CO2.