If a plant is exposed to a toxin that makes the thylakoid me

If a plant is exposed to a toxin that makes the thylakoid membranes permeable to protons, which of the following events do you predict will happen. Choose all that are correct.

Select one or more:

a. the proton gradient across the thylakoid membrane will increase

b. the oxidation of NADPH to NADP+ will decrease

c. the pH in the thylakoid lumen will increase

d. the production of ATP will decrease

Solution

The most important thing here is that everything revolves around proton gradient and electron transport, and these factors are controlled due to the selective permeability of the thylakoid membrane.

If the toxin makes the thylakoid membrane more permeable to protons then the whole photosystem will be disrupted and the electron transport chain will be ineffective in doing its job.

Here the Options C and D will hold true, this is because protons are actively transported across the thylakoid membrane with the help of electron transport chain and this helps maintain a low pH in the thylakoid as compared to the storma, which is the reason for the need of active transport in the first place and when the pH in the thylakoid increases as protons accumulate the proton gradient forces the H⁺ ions to go across the ATP synthases thus producing ATP, but when the membrane permeability is altered by the toxin there is no need of this mechanism, and therefore the production of ATP will decrease.