A chloroplast has 40 grana. Each granum is a stack of 15 thylakoids…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A chloroplast has grana. Each granum is a stack of thylakoids. A mesophyll cell has such chloroplasts. (a) How many thylakoids are in one chloroplast? (b) How many grana are in one cell? (c) Why does a chloroplast stack its thylakoids, in place of using one large sheet?
Need a reminder? The key ideaShow
A chloroplast has an outer and an inner membrane, the stroma, thylakoids stacked as grana, stroma lamellae joining the grana, and the lumen inside each thylakoid. Chlorophyll and the light reactions are in the thylakoid membranes (ATP and NADPH are made there). The enzymes of the biosynthetic phase are in the stroma. Chloroplasts lie mainly in the mesophyll cells.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Thylakoids in a chloroplast. thylakoids.
Step 2. Grana in a cell. grana.
Step 3. Why stack them. A stack packs a large amount of membrane into a small space. The membrane holds the pigments and the enzymes that capture light, so more membrane means more light trapped.
Answer: (a) thylakoids; (b) grana; (c) stacking fits a large light-trapping membrane into a small chloroplast.
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