A cell lining an air passage carries 250 cilia on its free surface…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A cell lining an air passage carries cilia on its free surface. Each cilium has the usual eukaryotic structure, and each grows from its own basal body. Count a doublet as two microtubules and a triplet as three.
- How many microtubules are there in the axoneme of one cilium?
- How many microtubules are there in the axonemes of all cilia together?
- How many radial spokes does one axoneme have?
- How many microtubules are there in one basal body?
- How many microtubules are there in all the axonemes and basal bodies of this cell together?
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.
Plan. Count the microtubules of one cilium and of one basal body, then multiply by the number of cilia.
(a) One axoneme. The axoneme usually has nine pairs of doublets of radially arranged peripheral microtubules and a pair of centrally located microtubules (the array). That is microtubules.
(b) All the axonemes. microtubules.
(c) Radial spokes. The central sheath is joined to one tubule of each peripheral doublet by a radial spoke. There are nine doublets, so there are radial spokes.
(d) One basal body. Cilia emerge from centriole-like structures called basal bodies. A centriole has nine evenly spaced peripheral fibrils of tubulin, and each fibril is a triplet: microtubules. The central hub is proteinaceous and adds none.
(e) Everything together. microtubules.
Answer: (a) microtubules. (b) microtubules. (c) radial spokes. (d) microtubules. (e) microtubules.
Check. One cilium with its basal body has microtubules, and . The two counts agree.
Watch out. The cilium has doublets and a central pair; the basal body, like a centriole, has triplets and no central microtubules. Do not use for the basal body.
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