A cell in a root tip is roughly a cube of side 24 µm…
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 in a root tip is roughly a cube of side µm. Four of its faces touch neighbouring cells. Suppose each square micrometre of shared wall carries plasmodesmata. (a) What area of wall does it share with its neighbours? (b) About how many plasmodesmata join it to them? (c) As this cell matures, where will its secondary wall form?
Need a reminder? The key ideaShow
The cell wall is a non-living, rigid layer outside the plasma membrane of fungi and plants. It gives shape, protects from mechanical damage and infection, helps cell-to-cell interaction and keeps out unwanted large molecules. Algae: cellulose, galactans, mannans, calcium carbonate. Land plants: cellulose, hemicellulose, pectins, proteins. Primary wall: young, can grow. Secondary wall: on the inner side, towards the membrane. Middle lamella: calcium pectate, holds cells together. Plasmodesmata: strands joining the cytoplasm of neighbouring 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. Shared area. One face: µm². Four faces: µm².
Step 2. Plasmodesmata. .
Step 3. The secondary wall. It forms on the inner side of the primary wall, towards the cell membrane.
Answer: (a) µm²; (b) about plasmodesmata; (c) on the inner side of the primary wall.
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