These polysaccharides (made from a variety of sugars, including galactose, xylose, arabinose) are found together with cellulose in the plant cell walls. If the cellulose fibrils are the reinforcing bars in the cell walls, the amorphous hemicelluloses and pectic substances are a sort of jelly-like cement in which the bars are embedded. Their significance for the cook is that, unlike cellulose, they are partly soluble in water, and therefore contribute to the softening of cooked vegetables and fruits. Pectin is abundant enough to be extracted from citrus fruits and apples and used to thicken fruit syrups into jams and jellies. These carbohydrates are described in detail in chapter 5.