Please use the following information to answer the question(s) below.
Paulinella chromatophora is one of the few cercozoans that is autotrophic, carrying out aerobic photosynthesis with its two elongated "cyanelles." The cyanelles are contained within vesicles of the host cell, and each is derived from a cyanobacterium, though not the same type of cyanobacterium that gave rise to the chloroplasts of algae and plants.
-If true, which of the following is the best evidence that the cyanelles are providing nutrition (in other words, calories) to the surrounding cercozoan?
A) if the cyanelle performs aerobic photosynthesis
B) if the vesicle membrane that surrounds each cyanelle possesses glucose-transport proteins
C) if the cyanelle performs aerobic respiration
D) if radiolabeled 14CO₂ enters the cyanelle and if, subsequently, radiolabeled glucose is present in cercozoan cytosol

Question

Quizplus · Accepted Answer

The best evidence that the cyanelles are providing nutrition to the surrounding cercozoan is if radiolabeled 14CO₂ enters the cyanelle and if, subsequently, radiolabeled glucose is present in cercozoan cytosol, indicating that the carbon fixed by the cyanelle during photosynthesis is being used by the host for energy production. Options A and C refer to metabolic processes of the cyanelles themselves, not their contribution to the host cell's nutrition. Option B refers only to glucose transport, which does not necessarily indicate the source of the glucose.

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