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 of Amino Acids with Ionizable R-Groups

Biochemistry

3. Amino Acids

Isoelectric Point of Amino Acids with Ionizable R-Groups

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Multiple Choice

What is the pI of His?

7.59

6.58

3.91

5.5

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Verified step by step guidance

Identify the ionizable groups in histidine: the carboxyl group (pKa2 = 1.82), the amino group (pKa1 = 9.17), and the imidazole side chain (pKR = 6.0).

Determine the charge of each group at different pH values: the carboxyl group is negatively charged above pH 1.82, the amino group is positively charged below pH 9.17, and the imidazole group is positively charged below pH 6.0.

To find the isoelectric point (pI), identify the pH at which the molecule has a net charge of zero. This occurs when the positive and negative charges balance each other.

For histidine, the pI is calculated by averaging the pKa values that correspond to the ionization states where the net charge is zero. In this case, average the pKa values of the amino group and the imidazole side chain: (pKa1 + pKR) / 2.

Calculate the average: (9.17 + 6.0) / 2. This will give you the pI of histidine.