Question

The cell wall composition is of
A. Cellulose and proteins
B. Hemicellulose and pectin
C. Microfibrils
D. All of the above

Answer 1

Hint: Cell wall is a tough, flexible and rigid layer which is responsible for giving structural support and protection. It is found in most prokaryotic cells, plant cells, algae, fungi but not in animal cells. Its composition varies from species to species.

Complete answer:
A cell wall is an elaborate extracellular matrix that covers each and every cell in most of the eukaryotes and prokaryotes except animals. In 1663 Robert Hooke saw the cell wall of the cork cells for the first time under the microscope. After seeing these cells under the microscope he named them so (cells). The walls of the neighbouring cells are cemented together to make an intact structure which is much more rigid, thicker and stronger compared to the animal cells. A cell plate is formed between daughter cells during cell division at the cytokinesis phase which is responsible for the formation of cell walls. The daughter cells are formed in the meristematic regions in case of plants and are very small and grow in size as they mature. Newly formed daughter cells have a primary cell wall which provides elasticity being thin and flexible, it accommodates cell material and as the cell grows till a certain time this cell material accommodation stops and layers are being added to the primary cell wall that makes it secondary.
Primary cell wall is made up of cellulose, hemicellulose and pectin. When the primary cell wall converts to a secondary cell wall then a polymer named lignin is added that is a recalcitrant and tough material. Some other material like suberin, cutin are also found and in case of algae glycoproteins and polysaccharides like carrageenan and agar are found, in case of bacteria peptidoglycan is present. Diatoms have cell walls made up of biogenic silica, fungi have chitin, archaea has pseudopeptidoglycan. Cellulose is arranged in the form of microfibrils, these help in cell expansion and is a key factor responsible for the growth and morphogenesis of the plant.

So the answer for this question is – Option D, All of the above.

Note:
Many algae have a mucilaginous covering around itself made up of exopolysaccharides. Some organisms release their cell walls and they produce deposits of silica and calcium carbonate because their cell wall is made up of inorganic material.