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

Liver vs Muscle Glycogen Phosphorylase

Biochemistry

8. Protein Function

Liver vs Muscle Glycogen Phosphorylase

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Multiple Choice

A patient comes into your clinic suffering from anorexia nervosa. Her mother brought her in concerned as the patient has not eaten in over 3 days. She has the classic presentation including low body weight, decreased muscle mass, decreased glycogen, and decreased fat stores, and she is anemic (low red blood cell count). What would be the expected phosphorylation state and activity of the patient's liver glycogen phosphorylase?

Phosphorylated & active.

Dephosphorylated & active.

Phosphorylated & inactive.

Dephosphorylated & inactive.

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Verified step by step guidance

Understand the role of glycogen phosphorylase: Glycogen phosphorylase is an enzyme that breaks down glycogen into glucose-1-phosphate, which can then be converted into glucose-6-phosphate for energy production. It is regulated by phosphorylation, which affects its activity.

Consider the metabolic state of the patient: The patient has not eaten for over 3 days, indicating a fasting state. During fasting, the body needs to mobilize stored energy sources, such as glycogen, to maintain blood glucose levels.

Determine the hormonal regulation during fasting: In a fasting state, glucagon levels are elevated, and insulin levels are low. Glucagon activates protein kinase A (PKA), which phosphorylates glycogen phosphorylase, thereby activating it.

Assess the phosphorylation state: Given the fasting state and the hormonal signals, glycogen phosphorylase in the liver is expected to be phosphorylated, which is the active form of the enzyme.

Conclude the expected activity: Since the enzyme is phosphorylated, it is active, allowing the liver to break down glycogen to release glucose into the bloodstream, helping to maintain energy levels during fasting.