Light reaction occurs inans.Chloroplast membraneGranaStromaMatrix Previous Marked for Review Next

Answer

The light reactions of photosynthesis occur within the thylakoid membranes of the chloroplasts. These processes involve the absorption of sunlight and the conversion of that energy into chemical energy in the form of ATP and NADPH.

1. Chloroplast: This is the organelle where photosynthesis takes place, but specifically, the light reactions take place in the structures within it.
2. Thylakoid Membrane: The light-dependent reactions occur in the thylakoid membranes, where light is absorbed, water is split, and oxygen is released as a byproduct.
3. Grana: This refers to stacks of thylakoids within the chloroplast; the light reactions specifically occur in the membranes of these thylakoids.
4. Stroma and Matrix: The stroma is the fluid surrounding the thylakoids where the Calvin cycle (light-independent reactions) occurs, while the term "matrix" usually refers to the inner compartment of mitochondria and is not relevant in the context of chloroplasts.

Thus, while the entire chloroplast is involved in photosynthesis, light reactions specifically take place within thylakoid membranes, often housed in structures called grana.