Table of contents

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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

7. Enzyme Inhibition and Regulation

Enzyme Inhibition

Biochemistry

7. Enzyme Inhibition and Regulation

Enzyme Inhibition

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Multiple Choice

When protein kinase A (PKA) is inactive, which of the following best describes its state?

PKA is bound to cAMP, leading to activation of its catalytic subunits.

The catalytic subunits are free and actively phosphorylating target proteins.

PKA is degraded by proteasomes in the cytoplasm.

The regulatory and catalytic subunits are bound together, preventing substrate phosphorylation.

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Verified step by step guidance

Understand the structure of protein kinase A (PKA): PKA is a holoenzyme composed of two regulatory subunits and two catalytic subunits. When inactive, these subunits are bound together.

Recognize the role of the regulatory subunits: The regulatory subunits inhibit the activity of the catalytic subunits by physically blocking their ability to phosphorylate target proteins.

Learn the activation mechanism: PKA becomes active when cyclic AMP (cAMP) binds to the regulatory subunits. This binding causes a conformational change, releasing the catalytic subunits.

Clarify the inactive state: In the absence of cAMP, the regulatory and catalytic subunits remain bound together, preventing the catalytic subunits from phosphorylating substrates.

Conclude the correct description: The inactive state of PKA is best described as the regulatory and catalytic subunits being bound together, which prevents substrate phosphorylation.