Apentix/AP Biology/Unit 3: Cellular Energetics/Question
AP Biologymediummcq1 pt

In a chloroplast, photosystems and ATP synthase sit embedded in thylakoid membranes while rubisco and the sugar building enzymes float in the stroma. How does this arrangement support efficient photosynthesis?

A.It separates the two halves of photosynthesis while still letting their energy carriers exchange rapidly
B.It confines light absorption to the stroma, where photons strike rubisco directly
C.It keeps the Calvin cycle isolated so it never shares compounds with the light reactions
D.It lets the stroma store the proton gradient while thylakoids fix CO2

Explanation

Core Concept

Compartmentalization supplies each stage with what it needs. The sealed thylakoid interior lets electron transport concentrate protons into a steep gradient, the potential energy reserve that ATP synthase taps. Housing rubisco and the soluble Calvin cycle enzymes in the surrounding stroma places them right beside the ATP and NADPH streaming out of the membrane. Short diffusion distances and organized membranes minimize losses between light harvesting and carbon fixation.

Correct Answer

AIt separates the two halves of photosynthesis while still letting their energy carriers exchange rapidly

More Unit 3: Cellular Energetics practice questions

Try a random question →

Practice more AP Biology questions with full explanations

Practice Unit 3: Cellular Energetics Questions →