Doesn’t stroma and thylakoid membrane contain proton pumps as well?
Hi!
The stroma is the fluid-filled internal space of the chloroplasts, and proton pumps are found on membranes, so this cannot be a place we find them. The same holds true for the gap between the thylakoid membranes.
Granum are the stacks of thylakoids, and thylakoids are the site of the light reaction, which requires proton pumps. Thus only 3 is true.
Hope it helps:)
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Ujjwal is right!
Also be careful about a trick here:
A thylakoid (or granum) only has a SINGLE membrane, while the chloroplast has a DOUBLE membrane (inner and outer membranes).
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