A palisade cell of a leaf has a volume of 15 000 µm³…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A palisade cell of a leaf has a volume of µm³. Its central vacuole fills per cent of it. (a) What is the volume of the vacuole? (b) What volume is left for the cytoplasm, the nucleus and the chloroplasts? (c) Name the membrane round the vacuole. (d) The vacuole holds more potassium ions than the cytoplasm does. How is this possible?
Need a reminder? The key ideaShow
Endomembrane system: ER, Golgi complex, lysosomes and vacuoles, with coordinated functions; not mitochondria, chloroplasts or peroxisomes. Rough ER: ribosomes, protein synthesis and secretion. Smooth ER: lipids, and steroid hormones in animal cells. Golgi apparatus: stacked cisternae with a cis (forming, convex) face and a trans (maturing, concave) face; packaging; glycoproteins and glycolipids. Lysosomes: from the Golgi, hydrolases active at acidic pH. Vacuoles: bound by the tonoplast, up to 90 per cent of a plant cell; contractile vacuoles in Amoeba; food vacuoles in protists.
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. The vacuole. µm³.
Step 2. The rest. µm³.
Step 3. The membrane. The tonoplast.
Step 4. More potassium. The tonoplast moves ions into the vacuole against their concentration gradient, so they collect there.
Answer: (a) µm³; (b) µm³; (c) the tonoplast; (d) the tonoplast carries the ions in against their gradient.
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