Question

Atrazine is an herbicide that prevents plant growth by inhibiting photosynthesis. Atrazine works by binding to proteins in the electron transport chain of photosystem II. Once atrazine binds to the proteins, electrons can no longer travel down the chain to reach photosystem I. Based on this information, how does atrazine stop plant growth?

Answer 1

Answer: C

Explanation:

A.

It prevents the formation of NADH and FADH2, which are needed by the light-independent reactions to fix carbon.

B.

It prevents chlorophyll from creating electrons, which are needed by the light-dependent reactions to make sugars.

C.

It prevents the formation of ATP and NADPH, which are needed by the light-independent reactions to make sugars.

D.

It prevents water from releasing oxygen, which is needed by the light-dependent reactions to fix carbon.

Answer 2

This electron transport chain of photosystem II helps the chlorophyll molecules in the plant leaves to tap the energy in the light photons. This energy is used to split a water molecule into hydrogen and oxygen atoms. The hydrogen is used to reduced carbon dioxide to make carbohydrates. Therefore, Atrazine stops photosynthesis by inhibiting the capacity of the plant to harness energy from sunlight for photosynthesis.