Practice question

Diatoms within stramenopile lineage secrete elaborate box-like cell wall termed frustule composed predominantly of hydrated amorphous silica polymerized as opal SiO2·nH2O, comprising two overlapping halves epitheca and hypotheca with intricate perforations, ribs, and spines visualized in scanning electron microscopy. Silicic acid uptake via SIT transporters and deposition in silica deposition vesicle mediated by silaffins and long-chain polyamines guides patterning. Frustule provides mechanical protection against grazing, contributes to rapid sinking and fossilization forming diatomaceous earth. Chemistry distinguishes diatoms from cellulose, chitin, or carbonate walled organisms.