A chloroplast is a cellular organelle unique to plants.
Structure of chloroplasts
A chloroplast is an organelle unique to plant cells, likely the product of the endosymbiosis of cyanobacteria by a primitive eukaryotic cell. The chloroplast is, in fact, separated from the cytoplasm by a double membrane, two membranes separated by an intermembrane space.
Internally, chloroplasts are comprised of stacks of thylakoids, which swim in the stroma (the intrachloroplastic fluid).
Function of the chloroplast
Photosynthesis takes place within the chloroplast. In particular, it takes place in the photosystems fixed into the membranes of the thylakoids. Chlorophyll, which gives plants a green colour, is found in these photosystems and has the role of capturing sunlight and converting it into energy during photosynthesis.
In plants, photosynthesis takes place within the chloroplast. © Kristian Peters, Wikimedia, CC by-sa 3.0