Inside a chloroplast, there are flattened sacs of photosynthetic membranes, called thylakoids.
- They are the site of the light-dependent reactions of photosynthesis.
- Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen (an aqueous space inside the thylakoid.
- The thylakoid plays an important role for photophosphorylation during photosynthesis.
During the light-dependent reaction, protons are pumped across the membrane into the lumen, making it acidic.
In short
- Thylakoids are small fluid-filled sacs, stacked up in the chloroplast into grana.
- The grana are linked together by a thin layer called lamellae.