Direct Answer
The cell walls of diatoms are made up of silica and form a hard, glass-like covering called a frustule. This frustule consists of two thin, overlapping halves (valves) that fit together like the two parts of a soap box or petri dish.
Key Features of Diatom Cell Wall
- Siliceous nature: The cell wall is impregnated with silica (\(\text{SiO}_2\)), making it very hard and almost indestructible.
- Frustule structure: The siliceous cell wall is called a frustule. It has two overlapping parts: the larger upper valve (epitheca) and the smaller lower valve (hypotheca), which fit into each other like a lid and box.
- Patterned surface: The frustule often shows fine and beautiful patterns due to the deposition of silica in various designs.
- Diatomaceous earth: When diatoms die, their siliceous cell walls accumulate on the sea or lake floor and form deposits called diatomaceous earth (or diatomite), which is soft, porous and chemically inert.
Short Exam-style Answer
In diatoms, the cell wall is made up of silica and forms a hard shell called a frustule, consisting of two overlapping valves that fit together like a soap box. Because of the siliceous nature, the cell walls are highly durable and on accumulation form diatomaceous earth.