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

7. Enzyme Inhibition and Regulation

Enzyme Inhibition

Biochemistry

7. Enzyme Inhibition and Regulation

Enzyme Inhibition

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Multiple Choice

Which of the following best explains how DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) affects the photosynthetic electron transport chain?

It inhibits electron flow by blocking the transfer of electrons from photosystem II to plastoquinone.

It acts as a competitive inhibitor of the enzyme RuBisCO.

It stimulates the reduction of NADP$^+$ to NADPH at photosystem I.

It increases the rate of ATP synthesis by enhancing proton gradient formation.

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Verified step by step guidance

Understand the role of DCMU in photosynthesis: DCMU is a herbicide that specifically targets the photosynthetic electron transport chain. It is known to interfere with the transfer of electrons between photosystem II (PSII) and plastoquinone.

Recall the function of photosystem II: PSII is responsible for capturing light energy and using it to excite electrons, which are then transferred to plastoquinone in the electron transport chain. This step is crucial for the continuation of the chain and subsequent ATP and NADPH production.

Analyze the mechanism of DCMU: DCMU binds to the plastoquinone binding site in PSII, preventing the transfer of electrons from PSII to plastoquinone. This blockage halts the electron transport chain, disrupting the formation of the proton gradient and ATP synthesis.

Eliminate incorrect options: DCMU does not act as a competitive inhibitor of RuBisCO, as RuBisCO is involved in carbon fixation, not the electron transport chain. It also does not stimulate NADP$^+$ reduction at photosystem I or enhance ATP synthesis, as its effect is inhibitory.

Conclude the correct explanation: The best explanation is that DCMU inhibits electron flow by blocking the transfer of electrons from photosystem II to plastoquinone, thereby disrupting the photosynthetic electron transport chain.