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

8. Protein Function

Glycogen Phosphorylase

Biochemistry

8. Protein Function

Glycogen Phosphorylase

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Multiple Choice

Glycogen phosphorylase is an enzyme involved in glycogen metabolism that's regulated by phosphorylation. Phosphorylation on serine residues results in more enzyme activity, while the dephosphorylated enzyme has little to no activity. What result would you expect on activity if the serine residues that served as phosphorylation sites on glycogen phosphorylase were mutated to aspartate residues?

No effect on activity, since aspartate residues can be phosphorylated similarly to serine residues.

The enzyme would be completely inactive if it has an Asp residue, since it will no longer recognize its substrate.

The enzyme likely has some activity, since Asp is negatively charged like a phosphoryl group, but activity would not be regulated by phosphorylation.

The enzyme would be mostly inactive, since the enzyme can no longer be phosphorylated.

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Verified step by step guidance

Understand the role of glycogen phosphorylase: It is an enzyme that breaks down glycogen into glucose-1-phosphate, and its activity is regulated by phosphorylation at serine residues.

Recognize the importance of phosphorylation: Phosphorylation adds a negatively charged phosphate group to serine residues, which increases the enzyme's activity by altering its conformation.

Consider the chemical properties of aspartate: Aspartate is an amino acid with a side chain that carries a negative charge, similar to the phosphate group added during phosphorylation.

Evaluate the effect of mutating serine to aspartate: While aspartate is negatively charged, it does not undergo phosphorylation. Therefore, the enzyme's activity might be affected since the regulatory mechanism of phosphorylation is lost.

Conclude the expected outcome: The enzyme may retain some activity due to the negative charge of aspartate, but it would not be regulated by phosphorylation, potentially leading to altered or reduced activity compared to the phosphorylated form.