Question

Which of the following statements is/are correct?

• A. When four, five or six amino acids are linked, the respective products are known as tetrapeptide, pentapeptide, or hexapeptide
• B. Polypeptide with more than hundred amino acid residues, having molecular mass higher than $10000 u$ is called protein
• C. Polypeptide with fewer amino acids are called proteins if they have well defined conformation of protein such as insulin
• D. All of the above

Answer 1

Answer: (D)

When four, five or six amino acids are linked, the respective products are known as tetrapeptide, pentapeptide or hexapeptide respectively. When the number of such amino acids is more than ten, then the products are called polypeptides. A polypeptide with more than hundred amino acid residues, having molecular mass higher than $10000\, u$ is called a protein.
The distinction between a polypeptide and a protein is not very sharp. Polypeptides with amino acids are likely to be called proteins if they ordinarily have a well defined conformation of a protein such as insulin which contains 51 amino acids.