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Subject - cell biology

The cytoplasm is the area of the cell surrounding the nucleus and enclosed by the cell membrane. This term also encompasses the protoplasm without the cell nucleus. The cytoplasm consists of cytosol and the cell organelles; the cytosol is the soluble portion of the cytoplasm, which cannot be divided into smaller fractions through centrifugation. It contains high concentrations of numerous proteins, including enzymes, as well as various metabolic products and other small molecules. All together, the cytoplasm is comprised of ca. 70 % water and about 15-20 % proteins. It is criss-crossed by a network of protein filaments, which form the cytoskeleton. Many important metabolic reactions take place in the cytoplasm; these include glycolysis, the pentose phosphate cycle, and biosynthesis of fatty acids.