[Model Answer QP2022 GS3] Each year a large amount of plant material, cellulose, is deposited on the surface of Planet Earth. What are the natural processes this cellulose undergoes before yielding carbon dioxide, water and other end products?

Cellulose, a complex carbohydrate, or polysaccharide, consisting of 3,000 or more glucose units. The basic structural component of plant cell walls, cellulose comprises about 33 percent of all vegetable matter (90 percent of cotton and 50 percent of wood are cellulose) and is the most abundant of all naturally occurring organic compounds.
Non Digestible by humans, cellulose is a food for herbivorous animals (e.g., cows, horses) because they retain it long enough for digestion by microorganisms present in the alimentary tract; protozoans in the gut of insects such as termites also digest cellulose. 
Of great economic importance, cellulose is processed to produce papers and fibres and is chemically modified to yield substances used in the manufacture of such items as plastics, photographic films, and rayon.

Natural processes undergone by cellulose while undergoing degradation i.e. before yielding carbon dioxide, water and other end products

1. Fragmentation: is the process of breaking of detritus into small pieces by detrivores such as earthworm.
2. Leaching: is the process of releasing nutrients in the water and seeping into the soil.
3. Catabolism: is the process of breaking down of complex molecules into the simpler molecules by microorganisms such as Bacteria and Fungi
4. Humification: is the process of formation of dark colored substance humus on the soil. It undergoes microbial action at a slow rate. 
5. Mineralization:  is the process of degradation of the hummus to release inorganic nutrients.
Finally the inorganic nutrients released during mineralisation is taken up by the plants and Biosynthesis of cellulose takes place. The dead and decaying matter will undergo the same 5 processes explained above to yield carbon dioxide, water and other end products. 

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