Chloroplasts

• Chloroplasts are well adapted to their function
• Chloroplasts are the organelle in plant cells where photosynthesis occurs
• each chloroplasts has a double membrane called the thylakoid membrane
• Chloroplasts are filled with a fluid known as the stroma
• The stroma is the site of the light dependent stage of photosynthesis
• A separate system of membranes are found in the stroma, these systems are the site of the light-dependent stage of photosynthesis
• Membrane system in the stroma is the site of the light dependent stage of photosynthesis
• membrane contains the pigments, enzymes and electron carriers required for the light dependent reactions
• this membrane system consists of a series of flattened, fluid-filled sacs known as thylakoids
• thylakoids stack up to form structures known as grana (singular: granum)
• Grana are connected by memranous channels called stroma lamellae which ensure the stacts of sacs are connected but distanced from one another
• membranes of grana create large surface area to increase number of light-dependent reactions that can occur
• membrane system provides a large number of pigment molecules in an arrangement that ensures as much light as necessary is captured
• stroma contains 70s ribosomes, a loop of DNA and starch grains
• the loop of DNA codes for some of the chloroplast proteins (others are coded for by DNA in plant cell nucleus)
• The protiends coded for by this loop are produced at the 70s ribosomes
• sugars formed during photosynthesis are stored as starch inside starch grains
• Diagram