Thylakoids are disc-shaped structures present in the chloroplast. They stack up to form the grana. Thylakoids are the sites for oxygenic photosynthesis in eukaryotic plants and algae.
What are grana and stroma?
- Grana are stacks of membrane-bounded, flattened discoid sacs called thylakoids containing the molecules of chlorophyll. They are the main functional units of chloroplasts.
- Stroma is the homogenous matrix in which grana are embedded. The stroma contains a variety of photosynthetic enzymes, starch grains, DNA and ribosomes.
- Granum is the site of the light reaction during photosynthesis while stroma is the site of dark reaction.