Chapter 23, Problem 10RQ

What do a peptide, polypeptide, and protein all have in common?

To determine

The common character in peptide, polypeptide, and protein.

Answer to Problem 10RQ

The amino acid units are in common is a peptide, polypeptide, and protein.

Explanation of Solution

The carboxylic acids having an amino group are termed as amino acids. The general structure of amino acid has an amino $\left(-{\text{NH}}_2\right)$ group, carboxylic $\left(-\text{COOH}\right)$ group and a hydrogen atom attached to carbon atom along with a side chain. The variation in the nature of side chain imparts characteristic properties to amino acids.

The interaction of amino group of one amino acid with carboxylic acid group of another amino acid results in the formation of an amide linkage. A number of amino acid units are joined with each other through $-\text{CONH}-$ linkages and results in the formation of peptides. This linkage is named as peptide linkage.

The polypeptides are the peptides which are composed of around $10-100$ amino acid units whereas the proteins are the macro peptides which are composed of $>100$ amino acid units.

Thus, the character which is common in peptide, polypeptide, and protein is amino acid.

Conclusion:

Peptide is the biomolecule in which $-{\text{NH}}_2$ group of one amino acid is linked with $-\text{COOH}$ group of another amino acid. However, the polypeptide and protein are the polymers of peptide which are composed of $10-100$ and $>100$ amino acid units respectively. Therefore, they all have amino acid units in common.