Where do the light-dependent reactions of photosynthesis take place?

The light-dependent reactions of photosynthesis occur in the thylakoid membranes of the chloroplasts. During this process, chlorophyll absorbs light energy, which is then used to split water molecules, releasing oxygen and generating energy-rich compounds like ATP and NADPH. The thylakoid structures are specifically adapted to capture light and contain the necessary pigments and proteins involved in this initial stage of photosynthesis.

In contrast, the stroma is the fluid-filled space surrounding the thylakoids within the chloroplast, where the light-independent reactions (Calvin cycle) occur. The cytoplasm, the gel-like substance within cells, does not host these reactions. Additionally, mitochondria are the organelles primarily responsible for cellular respiration, not photosynthesis. The specificity of the thylakoid membranes for the light-dependent reactions is fundamental to the efficiency of the photosynthesis process.