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

Which of the following amino acids contains a positively charged (basic) side chain at physiological pH?

Glutamine

Serine

Lysine

Leucine

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Verified step by step guidance

Step 1: Understand the concept of physiological pH, which is typically around 7.4, and how amino acid side chains behave at this pH. Basic side chains are positively charged due to protonation at physiological pH.

Step 2: Recall the structure and properties of the amino acids listed. Glutamine and serine have neutral side chains, leucine has a hydrophobic side chain, and lysine has a basic side chain with an amino group (-NH3+).

Step 3: Analyze lysine's side chain. The amino group in lysine's side chain is protonated at physiological pH, giving it a positive charge.

Step 4: Compare lysine to the other amino acids listed. Glutamine has an amide group, serine has a hydroxyl group, and leucine has an aliphatic side chain. None of these are basic or positively charged at physiological pH.

Step 5: Conclude that lysine is the correct answer because its side chain is positively charged at physiological pH due to the protonation of its amino group.