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

Amino Acid Classifications

GOB Chemistry

18. Amino Acids and Proteins

Amino Acid Classifications

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Problem 44a

Textbook Question

Name and draw the structures of the amino acids that fit the following descriptions:
a. Contains a thiol group

Verified step by step guidance

Step 1: Understand the problem. The question asks for the name and structure of an amino acid that contains a thiol group. A thiol group is a functional group with the formula -SH, which is characteristic of certain amino acids.

Step 2: Recall the amino acids that contain a thiol group. In biochemistry, the amino acid cysteine is known to have a thiol (-SH) group in its side chain.

Step 3: Write the structure of cysteine. Cysteine has the following components: (1) an amino group (-NH₂), (2) a carboxyl group (-COOH), (3) a hydrogen atom, and (4) a side chain containing a thiol group (-CH₂-SH). These groups are all attached to a central alpha carbon.

Step 4: Draw the structure of cysteine. Represent the central alpha carbon with its four attachments: the amino group, carboxyl group, hydrogen atom, and the side chain (-CH₂-SH). Ensure the thiol group is clearly shown in the side chain.

Step 5: Label the structure. Clearly label the amino group, carboxyl group, alpha carbon, and the thiol-containing side chain to ensure the structure is complete and accurate.

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Key Concepts

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

Amino Acids

Amino acids are organic compounds that serve as the building blocks of proteins. Each amino acid consists of a central carbon atom, an amino group, a carboxyl group, a hydrogen atom, and a variable side chain (R group) that determines its unique properties. There are 20 standard amino acids, each with distinct characteristics that influence protein structure and function.

Thiol Group

A thiol group is a functional group characterized by the presence of a sulfur atom bonded to a hydrogen atom (-SH). In the context of amino acids, the thiol group is found in cysteine, which is notable for its ability to form disulfide bonds that stabilize protein structures. This group plays a crucial role in the biochemical properties of proteins.

Structural Representation of Amino Acids

The structural representation of amino acids typically includes a central carbon atom (alpha carbon) connected to an amino group, a carboxyl group, a hydrogen atom, and a side chain (R group). Drawing these structures involves depicting the connectivity of these groups, which is essential for understanding the chemical behavior and interactions of the amino acids in biological systems.

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Related Practice

Textbook Question

Glycine has the zwitterion structure shown. Draw the structure and give the net charge of glycine that will predominate at the indicated pH values (pI = 6.0).

b. pH 12.0

512

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Textbook Question

Consult Table 18.3 and draw alanine. Label the functional groups and give the three-letter abbreviation and the one-letter abbreviation. What group does the side chain fall into?

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Textbook Question

Draw the structure of glutamic acid at low pH, at high pH, and at the two forms that exist between low pH and high pH. Which of these structures represents the zwitterion?

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Textbook Question

Name and draw the structures of the amino acids that fit the following descriptions:

a. Contains an isopropyl group

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Textbook Question

At neutral pH, which of the following amino acids has a net positive charge, which has a net negative charge, and which is neutral? (Hint: Draw the various charged forms of each amino acid before deciding.)

a. Asparagine

b. Lysine

c. Proline

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Textbook Question

Which of the following forms of aspartic acid would you expect to predominate at low pH, neutral pH, and high pH?

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Textbook Question

Which form of aspartic acid in Problem 18.54 is the zwitterion? What is the pI for the zwitterion?

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Open Question

Classify each amino acid as polar, nonpolar, acidic, or basic.