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Ch.10 Proteins Workers of the Cell
Frost - General, Organic and Biological Chemistry 4th Edition
Frost4th EditionGeneral, Organic and Biological ChemistryISBN: 9780134988696Not the one you use?Change textbook
Chapter 6, Problem 20d

Identify the N-terminus and the C-terminus for each of the peptides in Problem 10.18.
d. IYP

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1
Understand the structure of peptides: Peptides are chains of amino acids linked by peptide bonds. Each peptide has two distinct 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.
Examine the peptide sequence provided in Problem 10.18 (refer to the peptide sequence in your textbook or materials). The sequence is written from the N-terminus to the C-terminus by convention.
Identify the N-terminus: Look at the first amino acid in the sequence. The free amino group (-NH2) on this amino acid marks the N-terminus of the peptide.
Identify the C-terminus: Look at the last amino acid in the sequence. The free carboxyl group (-COOH) on this amino acid marks the C-terminus of the peptide.
Label the N-terminus and C-terminus clearly: Once you have identified the ends, label them explicitly in the peptide sequence to ensure clarity. For example, write 'N-terminus' next to the first amino acid and 'C-terminus' next to the last amino acid.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

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.
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Peptides Concept 1

N-terminus and C-terminus

The N-terminus refers to the end of a peptide that has a free amino group (-NH2), while the C-terminus has a free carboxyl group (-COOH). These termini are essential for determining the directionality of the peptide and play a significant role in its function and interactions.
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Drawing & Naming Peptides Concept 2

Amino Acid Sequence

The sequence of amino acids in a peptide determines its properties and function. Each amino acid contributes to the overall structure and behavior of the peptide, making it important to analyze the sequence to accurately identify the N- and C-termini.
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Amino Acid Catabolism: Amino Group Example 2