Structure and role of chloroplasts in photosynthesis

• Chloroplasts are disc-shaped organelles surrounded by a double membrane. They are comprised of two distinct regions : the grana (thylakoid stacks) and the stroma.
• The grana are stacks of up to 100 disc-shaped structures called thylakoids. The thylakoids contain the chlorophyll pigment for photosynthesis, and some have inter-granal lamellae (tubular extensions joining adjacent grana).
• The stroma is a fluid-filled matrix that contains enzymes and other structures needed for photosynthesis, such as starch grains.
• The grana are where the light-dependent stage of photosynthesis occurs.
• The stroma is where the light-independent stage of photosynthesis occurs.