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 would be positively charged at physiological pH (approximately 7.4)?

Serine

Aspartic acid

Lysine

Glutamine

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Verified step by step guidance

Step 1: Understand the concept of physiological pH. Physiological pH is approximately 7.4, which is slightly basic. Amino acids can exist in different ionization states depending on the pH of their environment.

Step 2: Recall the properties of amino acid side chains. Amino acids with basic side chains, such as lysine, arginine, and histidine, tend to be positively charged at physiological pH due to the protonation of their side groups.

Step 3: Analyze the amino acids provided in the question. Serine has a hydroxyl (-OH) group, which is neutral at physiological pH. Aspartic acid has a carboxyl (-COOH) group in its side chain, which is negatively charged at physiological pH. Glutamine has an amide (-CONH2) group, which is neutral at physiological pH.

Step 4: Focus on lysine. Lysine has an amino (-NH3+) group in its side chain, which remains protonated and positively charged at physiological pH. This makes lysine the correct answer.

Step 5: Conclude that lysine is positively charged at physiological pH due to the protonation of its basic side chain, while the other amino acids listed are either neutral or negatively charged at this pH.