Chloroplast structure Original Scenario-Based Practice

Questions

1. 1.

   During a simulated microscopic journey inside a plant chloroplast, an automated probe enters through the double-membrane envelope into the fluid-filled compartment surrounding the grana, before puncturing a single thylakoid disk to sample its interior lumen. As the probe analyzes both distinct microenvironments during active photosynthesis under continuous light, the mission log compares their biochemical contents and chemical conditions. Which observation correctly characterizes the fluid stroma compared to the internal thylakoid lumen?

   • A) The stroma contains circular DNA, ribosomes, and Calvin cycle enzymes at a higher pH than the acidic lumen where protons accumulate.
   • B) The stroma possesses water-splitting enzyme complexes and a high proton concentration, whereas the lumen contains Rubisco and circular DNA.
   • C) The stroma is bounded by individual thylakoid membranes and holds the catalytic heads of ATP synthase directed inward toward the acidic lumen.
   • D) The stroma maintains an acidic environment due to photolysis, while the neutral lumen houses the enzymes responsible for carbon fixation.

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