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 is classified as a basic (positively charged) amino acid at physiological pH?

Serine

Leucine

Lysine

Glutamic acid

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Verified step by step guidance

Understand the classification of amino acids: Amino acids are categorized based on the properties of their side chains (R groups). At physiological pH (~7.4), amino acids can be neutral, acidic (negatively charged), or basic (positively charged). Basic amino acids have side chains that are positively charged due to protonation.

Identify the basic amino acids: The three amino acids classified as basic at physiological pH are lysine, arginine, and histidine. Their side chains contain functional groups that can accept protons, making them positively charged.

Analyze the options provided: Serine has a hydroxyl (-OH) group in its side chain, making it polar but uncharged. Leucine has a hydrophobic aliphatic side chain, making it neutral. Glutamic acid has a carboxylic acid group in its side chain, which is negatively charged at physiological pH. Lysine has an amino group (-NH3+) in its side chain, which is positively charged at physiological pH.

Determine the correct answer: Based on the analysis, lysine is the only amino acid in the list that is classified as basic (positively charged) at physiological pH.

Conclude the reasoning: Lysine's positively charged amino group in its side chain makes it a basic amino acid, distinguishing it from the other options provided.