Chloroplasts

• Chloroplasts are small, flattened organelles found in plant cells. They're the location for photosynthesis in plant cells.
• Chloroplasts have a double membrane called the chloroplast envelope.
• Thylakoids are stacked up in the chloroplast into structures called Grana. The grana are linked together by bits of thylakoid membrane called lamellae.
• Chloroplasts contain photosynthetic pigments. These are coloured substances that absorv the light energy needed for photosynthesis. These pigments are found in the thylakoid membrane attached to proteins which are called photosystems.
• The 4 main types of photosyntheic pigments are chlorophyll a, cholorphyll b, carotene and xanthrophyll.
• A photosystem contains two types of photosynthetic pigments - Primary and accessory pigments.
• Primary pigments are reaction centres, where electrons are excited during the light dependent reaction.
• Accessory pigments make up light-harlight-harvesting systems. These surround reaction centres and transfer light energy to them to boost the energy available for electron excitement to take place.
• There are two photosystems used by plants to capture light energy. Photosystem 1 absorbs light best at a wavelength of 700nm and photosystem 2 absorbs light best at 680nm.
• Contained within the inner membrane of the chloroplast and surrounding the thylakoids is a gel-like substance called the stroma. It contains enzymes, sugars and organic acids.
• Chloroplasts have their own DNA. It's found in the stroma and is often circular. There can be multiple copies in each chloroplast.
• Carbohydrates produced by photosynthesis and not used straight away are stored as starch gains in the stroma.