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Which is used to make cell walls ​

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Answer:

Figure 3 : Plant plasma membrane and cell-wall structure

A plant cell wall is arranged in layers and contains cellulose microfibrils, hemicellulose, pectin, lignin, and soluble protein. These components are organized into three major layers: the primary cell wall, the middle lamella, and the secondary cell wall (not pictured). The cell wall surrounds the plasma membrane and provides the cell tensile strength and protection.

© 2008 Nature Publishing Group Sticklen, M. B. Plant genetic engineering for biofuel production: towards affordable cellulosic ethanol. Nature Reviews Genetics 9, 433-443 (2008). All rights reserved. 

Figure Detail

Besides the presence of chloroplasts, another major difference between plant and animal cells is the presence of a cell wall. The cell wall surrounds the plasma membrane of plant cells and provides tensile strength and protection against mechanical and osmotic stress. It also allows cells to develop turgor pressure, which is the pressure of the cell contents against the cell wall. Plant cells have high concentrations of molecules dissolved in their cytoplasm, which causes water to come into the cell under normal conditions and makes the cell's central vacuole swell and press against the cell wall. With a healthy supply of water, turgor pressure keeps a plant from wilting. In drought, a plant may wilt, but its cell walls help maintain the structural integrity of its stems, leaves, and other structures, despite a shrinking, less turgid vacuole.

Plant cell walls are primarily made of cellulose, which is the most abundant macromolecule on Earth. Cellulose fibers are long, linear polymers of hundreds of glucose molecules. These fibers aggregate into bundles of about 40, which are called microfibrils. Microfibrils are embedded in a hydrated network of other polysaccharides. The cell wall is assembled in place. Precursor components are synthesized inside the cell and then assembled by enzymes associated with the cell membrane (Figure 3).

What Are Vacuoles?

Plant cells additionally possess large, fluid-filled vesicles called vacuoles within their cytoplasm. Vacuoles typically compose about 30 percent of a cell's volume, but they can fill as much as 90 percent of the intracellular space. Plant cells use vacuoles to adjust their size and turgor pressure. Vacuoles usually account for changes in cell size when the cytoplasmic volume stays constant.

Some vacuoles have specialized functions, and plant cells can have more than one type of vacuole. Vacuoles are related to lysosomes and share some functions with these structures; for instance, both contain degradative enzymes for breaking down macromolecules. Vacuoles can also serve as storage compartments for nutrients and metabolites. For instance, proteins are stored in the vacuoles of seeds, and rubber and opium are metabolites that are stored in plant vacuoles.

Conclusion

Plant cells have certain distinguishing features, including chloroplasts, cell walls, and intracellular vacuoles. Photosynthesis takes place in chloroplasts; cell walls allow plants to have strong, upright structures; and vacuoles help reg

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