Q.Within the chloroplast, the stacks of flattened, coin-like membranous sacs called grana, and the thylakoid membrane in general, are the principal site of the:

Photosynthesis in higher plants occurs chiefly within the chloroplast, a double-membrane-bound organelle abundant in leaf mesophyll cells. An outer and inner envelope membrane encloses the fluid stroma, which houses the Calvin cycle enzymes (including RuBisCO, widely cited as the most abundant protein on Earth), chloroplast DNA, 70S ribosomes and starch grains -- the site of the biosynthetic (dark) phase. Suspended within the stroma is an internal membrane system folded into flattened thylakoid sacs, stacked into grana and interconnected by unstacked stroma lamellae, together forming one continuous membrane enclosing a continuous …