Plasma membrane

Many eucaryotes do not have cell walls, so the plasma membrane represents the outermost layer of the cell. The sterols mentioned earlier are important in helping these cells to resist the effects of osmotic pressure. The only procaryotes to contain sterols are the mycoplasma, which are unusual in not possessing the typical bacterial cell wall. Although the eucaryotic plasma membrane does not have the role in cellular respiration associated with its procaryotic counterpart, it does have additional functions. The process of endocytosis (and its reverse, exocytosis), by which particles or large soluble molecules are enveloped and brought into the cell, is carried out at the plasma membrane. Also, carbohydrate residues in the membrane act as receptors for cell-to-cell recognition, and may be involved in cell adhesion.

Figure 3.17 The structures of (a) cellulose and (b) chitin. Cellulose is composed of repeating glucose units joined by f-1,4 linkages, and chitin is a polymer of N-acetylglucosamine

Figure 3.17 The structures of (a) cellulose and (b) chitin. Cellulose is composed of repeating glucose units joined by f-1,4 linkages, and chitin is a polymer of N-acetylglucosamine

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Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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