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

6. Enzymes and Enzyme Kinetics

Covalent Catalysis

Biochemistry

6. Enzymes and Enzyme Kinetics

Covalent Catalysis

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

An enzyme has two key catalytic residues, Glu 35 (pK_a= 5.9) and Asp 52 (pK_a= 4.5). Which of the following is likely true about the mechanism for this enzyme if the optimum pH = 5.2?

Glu 35 is more likely a nucleophile than Asp 52.

Glu 35 is more likely a general acid than Asp 52.

Both a and b are true.

a, b & c are false.

Previous problemNext problem

Verified step by step guidance

Understand the role of pKa in enzyme catalysis: The pKa value of an amino acid residue in an enzyme indicates the pH at which the residue is half ionized. This is crucial for determining whether a residue acts as a nucleophile or a general acid/base in the enzyme's mechanism.

Consider the optimum pH: The enzyme's optimum pH is 5.2, which is between the pKa values of Glu 35 (5.9) and Asp 52 (4.5). At this pH, Glu 35 is more likely to be protonated, while Asp 52 is more likely to be deprotonated.

Evaluate the nucleophilic potential: A nucleophile is typically deprotonated and negatively charged, making it more reactive. Since Asp 52 has a lower pKa and is more likely deprotonated at pH 5.2, it is more likely to act as a nucleophile than Glu 35.

Assess the general acid potential: A general acid donates a proton during catalysis. Glu 35, with a higher pKa, is more likely to be protonated at pH 5.2, making it more suitable to act as a general acid compared to Asp 52.

Conclude based on the analysis: Given the pKa values and the optimum pH, Glu 35 is more likely to act as a general acid, while Asp 52 is more likely to act as a nucleophile. Therefore, the statement 'Glu 35 is more likely a general acid than Asp 52' is true.