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

12. Biosignaling

Inhibitory Adenylate Cyclase GPCR Signaling

Biochemistry

12. Biosignaling

Inhibitory Adenylate Cyclase GPCR Signaling

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Multiple Choice

The addition of the nonhydrolyzable GTP-analog, GTPγS (shown below), is a common cell culture technique. If only affecting the inhibitory pathway, what effect would GTPγS have on cellular cAMP levels?

cAMP levels increase because adenylate cyclase can no longer hydrolyze GTP.

cAMP levels decrease because G_s remains in its inactive state and can no longer bind GDP.

cAMP levels decrease because G_i remains in its active state since it can no longer hydrolyze GTP.

cAMP levels increase because G_i remains in its inactive state since it can no longer hydrolyze GTP.

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Verified step by step guidance

Understand the role of GTP in cellular signaling: GTP is a molecule that binds to G-proteins, which are involved in transmitting signals from outside the cell to the inside. When GTP is bound, the G-protein is active; when GDP is bound, it is inactive.

Identify the effect of GTPγS: GTPγS is a nonhydrolyzable analog of GTP, meaning it can bind to G-proteins but cannot be hydrolyzed to GDP. This means that G-proteins remain in their active state when bound to GTPγS.

Focus on the inhibitory pathway: In the context of the problem, we are interested in the inhibitory G-protein (Gi). Normally, Gi inhibits adenylate cyclase, reducing cAMP levels when active.

Analyze the effect of GTPγS on Gi: Since GTPγS cannot be hydrolyzed, Gi remains in its active state, continuously inhibiting adenylate cyclase. This leads to a decrease in cAMP levels because adenylate cyclase activity is reduced.

Conclude the effect on cAMP levels: With Gi remaining active due to the presence of GTPγS, cAMP levels decrease as adenylate cyclase is inhibited and cannot produce cAMP efficiently.