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How are grana related to thylakoids in chloroplasts?
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Photosynthesis
Diagram of photosynthesis showing how water, light, and carbon dioxide are absorbed by a plant to produce oxygen, sugars, and more carbon dioxide.
In chloroplasts, thylakoids are closed, saclike hollow disks formed by the internal membranes known as lamellae.1
Grana are specific regions within the chloroplast where these thylakoids are tightly stacked together, appearing like stacks of disks when viewed under an electron microscope. While these stacks form the grana, some thylakoids extend through the stroma to connect different grana, creating a network where the aqueous spaces inside the thylakoids are linked. This complex structural organization is essential, as the light reactions of photosynthesis occur exclusively within these thylakoid membranes.1