Final answer:
The N and C terminus of a protein are the starting and ending points of the polypeptide chain, marked by free amino and carboxyl groups, respectively. The beta chain of hemoglobin is 147 residues long and the position of Val-1 and Arg-141 does not correspond to the C and N termini. Accurate identification of these termini is crucial for understanding protein structure and function, as demonstrated by the effect of mutations in sickle cell anemia.
Step-by-step explanation:
You are looking to locate the N and C terminus of hemoglobin. In proteins, the N terminus is represented by the first amino acid at the start of the polypeptide chain, which has a free amino group, while the C terminus corresponds to the last amino acid at the other end of the chain, which has a free carboxyl group.
In the case of hemoglobin, as reported for the beta chain, which is 147 residues in length, the N terminus would typically be represented by the amino acid sequence starting with Met (methionine), and the C terminus would be the end portion of the sequence. Since the beta chain has 147 amino acids, Val-1 would not be the C terminus, as it is often near the N terminus. Similarly, Arg-141 would be one of the amino acids towards the C terminus, but not the very last one in the beta chain of hemoglobin.
If we refer to the alpha chain of hemoglobin, which is made up of 141 amino acids, then the N terminus starts from the first amino acid, which is not necessarily Valine. It is important to note that in primary structure analysis, the sequence and specific number of amino acids determine the structure and function of the protein, such as in the case of sickle cell anemia where a single amino acid substitution of Valine for Glutamic Acid at position 6 in the beta chain can lead to the disease.