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

Isoelectric Point

Biochemistry

3. Amino Acids

Isoelectric Point

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Multiple Choice

What is the net charge on a phenylalanine molecule at pH 1?

-1

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Verified step by step guidance

Step 1: Understand the structure of phenylalanine. Phenylalanine is an amino acid with a carboxyl group (-COOH), an amino group (-NH2), and a side chain containing a benzyl group. At very low pH, both the amino group and the carboxyl group are protonated.

Step 2: Recall the pKa values of the functional groups in phenylalanine. The amino group typically has a pKa around 9-10, and the carboxyl group has a pKa around 2. At pH 1, the environment is highly acidic, meaning the pH is below the pKa of both groups.

Step 3: Determine the protonation state of the amino group (-NH2). At pH 1, the amino group will be protonated to form -NH3⁺, contributing a positive charge.

Step 4: Determine the protonation state of the carboxyl group (-COOH). At pH 1, the carboxyl group remains protonated as -COOH, contributing no charge.

Step 5: Calculate the net charge of the molecule. Since the amino group contributes a +1 charge and the carboxyl group contributes 0 charge, the net charge of phenylalanine at pH 1 is +1.