Identify the N-terminus and the C-terminus for each of the peptides in Problem 10.18.
a. Ala—Asn—Thr
b. DS

Verified step by step guidance

1. Understand the structure of peptides: Peptides are chains of amino acids linked by peptide bonds. Each peptide has two ends: the N-terminus (amino group, -NH2) and the C-terminus (carboxyl group, -COOH). The N-terminus is the starting point of the peptide chain, and the C-terminus is the ending point.
2. Examine the peptide sequence provided in Problem 10.18 (not included in the current problem statement). Identify the amino acid at the beginning of the sequence. The free amino group (-NH2) of this amino acid represents the N-terminus.
3. Identify the amino acid at the end of the peptide sequence. The free carboxyl group (-COOH) of this amino acid represents the C-terminus.
4. If the peptide sequence is written in the standard format (from N-terminus to C-terminus), the first amino acid in the sequence corresponds to the N-terminus, and the last amino acid corresponds to the C-terminus.
5. Label the N-terminus and C-terminus for each peptide in Problem 10.18 based on the sequence provided. Ensure that the N-terminus is marked with -NH2 and the C-terminus with -COOH for clarity.

Key Concepts

Peptide Structure

Peptides are short chains of amino acids linked by peptide bonds. Each peptide has a specific orientation, with an N-terminus (amino end) and a C-terminus (carboxyl end). Understanding this structure is crucial for identifying the termini of any peptide sequence.

Amino Acids

Amino acids are the building blocks of peptides and proteins. Each amino acid has a central carbon atom, an amino group, a carboxyl group, and a unique side chain. The sequence and composition of these amino acids determine the properties and functions of the peptide.

Terminology in Biochemistry

In biochemistry, the terms N-terminus and C-terminus refer to the ends of a peptide chain. The N-terminus is where the amino group is located, while the C-terminus is where the carboxyl group is found. Correctly identifying these termini is essential for understanding peptide synthesis and function.