Arun compares the cell walls of a red seaweed and a mango leaf…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Arun compares the cell walls of a red seaweed and a mango leaf. (a) Which substance would he find in both? (b) Name two substances found only in the seaweed's wall. (c) Name two found only in the mango leaf's wall. (d) Give two jobs that the wall does in both.
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. In both. Cellulose is in the walls of algae and of land plants.
Step 2. Only in the alga. Any two of galactans, mannans and calcium carbonate.
Step 3. Only in the land plant. Any two of hemicellulose, pectins and proteins.
Step 4. Jobs. The wall gives shape, protects from damage and infection, helps cells interact, and keeps out unwanted large molecules.
Answer: (a) cellulose; (b) two of galactans, mannans and calcium carbonate; (c) two of hemicellulose, pectins and proteins; (d) any two of shape, protection, cell-to-cell interaction and a barrier to large molecules.
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