Step 1: Understanding the Concept:
Peptides are polymers of amino acids linked by peptide bonds.
They are classified into different categories based on the length of the amino acid chain.
Step 2: Detailed Explanation:
Let us review the terminology used to classify peptide chains by length:
- Dipeptide: Contains exactly 2 amino acid residues.
- Tripeptide: Contains exactly 3 amino acid residues.
- Oligopeptide: A short chain of amino acids, typically defined as having between 2 and 10 amino acid residues (or "10 or less" residues).
The prefix "oligo-" is derived from the Greek word for "few."
- Polypeptide: A longer, unbranched chain of amino acids, typically containing more than 10 to 20 residues, up to about 50 residues.
- Protein: A complex polypeptide chain containing more than 50 amino acid residues that folds into a distinct three-dimensional structure.
Therefore, oligopeptides are defined as having 10 or less amino acid residues.
Step 3: Final Answer:
The term "oligopeptide" is used to describe chains containing 10 or less amino acid residues, which corresponds to Option (A).