Refer to the Table Below Showing Observations from Experiments Conducted

Multiple Choice

Refer to the table below showing observations from experiments conducted on three types of pea plants.One type of pea plant contained a mutation in the gene encoding thioredoxin that resulted in zero production of the protein thioredoxin.Another type contained two mutations: the same thioredoxin mutation as in the previous type and a mutation in the gene encoding the Calvin cycle enzyme phosphoribulokinase (PRK) that did not affect its expression.The third type contained no mutations in either gene and was designated as "wild type." Before the experiments, all plants were kept on a 14-hour light/10-hour dark cycle for several weeks. In conducting the experiments, researchers excised leaves either toward the end of a light cycle or toward the end of a dark cycle.Chloroplasts were then isolated and lysed to release the contents of the stroma, and PRK was assayed to determine its catalytic activity.Which statement about thioredoxin is consistent with these data?

A) Thioredoxin is an electron carrier protein that participates in the electron transport chain during photophosphorylation.
B) Thioredoxin is a regulatory molecule, becoming activated via light-induced changes and then activating PRK by shifting it from an inactive to an active conformation.
C) Thioredoxin is a regulatory molecule, shutting down Calvin cycle reactions by acting as an alternative to NADP⁺ as the final electron acceptor during the light reactions.
D) Thioredoxin is an enzyme that functions in carbon fixation as an alternative to the Calvin cycle enzyme rubisco.
E) Thioredoxin is an integral protein component of the thylakoid membrane that ensures that the membrane remains impermeable to protons.