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

Previous problemNext problem

Struggling with Biochemistry?

Join thousands of students who trust us to help them ace their exams!Watch the first video

Multiple Choice

Which functional group on an amino acid is polar and can become positively charged at physiological pH?

Methyl group (–CH$_3$)

Hydroxyl group (–OH)

Carboxyl group (–COOH)

Amino group (–NH$_2$)

Previous problemNext problem

Verified step by step guidance

Step 1: Understand the concept of physiological pH, which is typically around 7.4, and how it affects the ionization of functional groups on amino acids.

Step 2: Recall that the amino group (–NH₂) is a polar functional group due to the electronegativity difference between nitrogen and hydrogen, making it capable of forming hydrogen bonds.

Step 3: At physiological pH, the amino group (–NH₂) can accept a proton (H⁺) and become positively charged, forming –NH₃⁺. This occurs because the pH is below the pKa of the amino group, which is typically around 9-10.

Step 4: Compare the other functional groups listed in the problem: The methyl group (–CH₃) is nonpolar and cannot become charged, the hydroxyl group (–OH) is polar but does not typically gain a positive charge at physiological pH, and the carboxyl group (–COOH) is polar but loses a proton to become negatively charged (–COO⁻) at physiological pH.

Step 5: Conclude that the amino group (–NH₂) is the correct answer because it is polar and can become positively charged at physiological pH, forming –NH₃⁺.