Table of contents

1. Introduction to Biochemistry4h 34m
2. Water3h 23m
3. Amino Acids8h 10m
4. Protein Structure10h 4m
5. Protein Techniques14h 5m
6. Enzymes and Enzyme Kinetics13h 38m
7. Enzyme Inhibition and Regulation 8h 42m
8. Protein Function 9h 41m
9. Carbohydrates7h 49m
10. Lipids5h 49m
11. Biological Membranes and Transport 6h 37m
12. Biosignaling9h 45m
Review 1: Nucleic Acids, Lipids, & Membranes2h 47m
Review 2: Biosignaling, Glycolysis, Gluconeogenesis, & PP-Pathway3h 12m
Review 3: Pyruvate & Fatty Acid Oxidation, Citric Acid Cycle, & Glycogen Metabolism2h 26m
Review 4: Amino Acid Oxidation, Oxidative Phosphorylation, & Photophosphorylation1h 48m

3. Amino Acids

Amino Acid Groups

Biochemistry

3. Amino Acids

Amino Acid Groups

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Multiple Choice

Twenty different amino acids are found in the proteins of cells. What distinguishes these molecules from one another?

The structure of their side chains (R groups)

The number of peptide bonds they can form

The presence of a carboxyl group

The location of their amino group

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Verified step by step guidance

Understand that amino acids are the building blocks of proteins, and they share a common structure: a central carbon atom (α-carbon) bonded to an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and a unique side chain (R group).

Recognize that the side chain (R group) is the distinguishing feature of amino acids. It varies in structure, size, charge, and chemical properties, giving each amino acid its unique characteristics.

Eliminate the incorrect options: The number of peptide bonds an amino acid can form is not a distinguishing feature, as peptide bonds are formed between amino acids during protein synthesis. Similarly, the presence of a carboxyl group and the location of the amino group are common to all amino acids and do not differentiate them.

Focus on the correct answer: The structure of the side chains (R groups) is what distinguishes the 20 amino acids found in proteins. These side chains determine the chemical behavior and role of each amino acid in protein structure and function.

Conclude that understanding the diversity of side chains is essential for studying protein folding, interactions, and enzymatic activity in biochemistry.