cell wall is made up of which substance
Answers
Explanation:
cellulose microfibrils
cellulose microfibrilsThe cell wall is composed of a network of cellulose microfibrils and cross-linking glycans embedded in a highly cross-linked matrix of pectin polysaccharides. In secondary cell walls, lignin may be deposited.
Answer:
plant. It was the thick cell walls of cork, visible in a primitive microscope, that in 1663 enabled Robert Hooke to distinguish and name cells for the first time. The walls of neighboring plant cells, cemented together to form the intact plant (Figure 19-68), are generally thicker, stronger, and, most important of all, more rigid than the extracellular matrix produced by animal cells. In evolving relatively rigid walls, which can be up to many micrometers thick, early plant cells forfeited the ability to crawl about and adopted a sedentary life-style that has persisted in all present-day plants.
Plant cell walls. (A) Electron micrograph of the root tip of a rush, showing the organized pattern of cells that results from an ordered sequence of cell divisions in cells with relatively rigid cell walls. In this growing tissue, the cell walls are still (more...)
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The Composition of the Cell Wall Depends on the Cell Type
All cell walls in plants have their origin in dividing cells, as the cell plate forms during cytokinesis to create a new partition wall between the daughter cells (discussed in Chapter 18). The new cells are usually produced in special regions called meristems (discussed in Chapter 21), and they are generally small in comparison with their final size. To accommodate subsequent cell growth, their walls, called primary cell walls, are thin and extensible, although tough. Once growth stops, the wall no longer needs to be extensible: sometimes the primary wall is retained without major modification, but, more commonly, a rigid, secondary cell wall is produced by depositing new layers inside the old ones. These may either have a composition similar to that of the primary wall or be markedly different. The most common additional polymer in secondary walls is lignin, a complex network of phenolic compounds found in the walls of the xylem vessels and fiber cells of woody tissues.The plant cell wall thus has a “skeletal” role in supporting the structure of the plant as a whole, a protective role as an enclosure for each cell individually, and a transport role, helping to form channels for the movement of fluid in the plant. When plant cells become specialized, they generally adopt a specific shape and produce specially adapted types of walls, according to which the different types of cells in a plant can be recognized and classifie
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