Table of contents

1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

18. Amino Acids and Proteins

Peptides

GOB Chemistry

18. Amino Acids and Proteins

Peptides

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3:50 minutes

Problem 15a

Textbook Question

Consider the following tripeptide:

a. Circle the N-terminal amino acid, and give its name. Draw a square around the C-terminal amino acid, and give its name.

Verified step by step guidance

Step 1: Understand the structure of a tripeptide. A tripeptide consists of three amino acids linked by peptide bonds. The N-terminal amino acid is the one with a free amino group (-NH2), while the C-terminal amino acid is the one with a free carboxyl group (-COOH).

Step 2: Examine the provided image of the tripeptide. Identify the amino acid at the N-terminal (leftmost side of the structure) by locating the free amino group (-NH2). Circle this amino acid and note its name based on its side chain and structure.

Step 3: Identify the amino acid at the C-terminal (rightmost side of the structure) by locating the free carboxyl group (-COOH). Draw a square around this amino acid and note its name based on its side chain and structure.

Step 4: For the middle amino acid, observe its structure and confirm that it is connected to the N-terminal and C-terminal amino acids via peptide bonds. This amino acid does not have free amino or carboxyl groups.

Step 5: Review the names of the N-terminal and C-terminal amino acids you identified, ensuring they match the structural features and side chains visible in the image.

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Key Concepts

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

N-terminal and C-terminal

The N-terminal refers to the end of a peptide or protein that has a free amino group (-NH2), while the C-terminal is the end with a free carboxyl group (-COOH). In a tripeptide, the N-terminal amino acid is the first in the sequence, and the C-terminal is the last. Identifying these ends is crucial for understanding the structure and function of peptides.

Amino Acids

Amino acids are the building blocks of proteins and peptides, consisting of a central carbon atom, an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group). Each amino acid has a unique side chain that determines its properties and role in protein structure. Recognizing the specific amino acids at the N- and C-termini is essential for understanding the peptide's characteristics.

Peptide Structure

Peptides are short chains of amino acids linked by peptide bonds, formed through a dehydration reaction between the amino group of one amino acid and the carboxyl group of another. The sequence and arrangement of amino acids in a peptide dictate its three-dimensional structure and biological function. Understanding peptide structure is vital for analyzing how the N- and C-terminal amino acids influence the overall properties of the tripeptide.

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Related Practice

Textbook Question

Draw the condensed structural formula for each of the following peptides, and give its three-letter and one-letter abbreviations:

d. histidylglycylglutamylisoleucine

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Textbook Question

Peptides isolated from rapeseed that may lower blood pressure have the following sequence of amino acids. Draw the structure for each peptide and write the one-letter abbreviations.

a. Arg–Ile–Tyr

498

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Textbook Question

Peptides from sweet potato with antioxidant properties have the following sequence of amino acids. Draw the structure for each peptide and write the one-letter abbreviations.

b. Asn–Tyr–Asp–Glu–Tyr

768

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Textbook Question

Write the products for the following condensation or hydrolysis reactions:

458

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Textbook Question

Consider the amino acids glycine, proline, and lysine.

b. Using three-letter abbreviations for the amino acids, give the sequence for each of the possible tripeptides.

270

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