In biochemistry, fat is a generic term for a class of lipids. Fats are produced by organic processes in animals and plants. All fats are insoluble in water and have a density significantly below that of water (i.e. they float on water.) Fats that are liquid at room temperature are often referred to as oil.
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Products with a lot of saturated fats tend to be solid at room temperature, while products containing unsaturated fats, which include monounsaturated fats and polyunsaturated fats, tend to be liquid at room temperature.
Predominantly saturated fats (solid at room temperature) include all animal fats (e.g. milk fat, lard, tallow), as well as palm oil, coconut oil, cocoa fat and hydrogenated vegetable oil (shortening[?]). All other vegetable fats, such as those coming from olive, peanut, maize (corn oil[?]), cottonseed[?], sunflower, safflower[?], and soybean, are predominantly unsaturated and remain liquid at room temperature. However, both vegetable and animal fats contain saturated and unsaturated fats. Some oils (such as olive oil) contain in majority monounsaturated fats, while others present quite a high percentage of polyunsaturated fats (sunflower, rape).
Energy is stored as fatty tissue when the nutrition/energy content of the blood remains higher than is consumed by muscular and other activity. When the energy content in the blood lessens, the fatty tissue reacts by releasing a corresponding amount of energy from the fat cells. This activity is controlled by insulin and other hormones in the body.
Different varieties of fat has seen, and indeed still see, much use as lubricants, although recently various synthetic[?] substances and petroleum derivatives has taken over in most industrial applications. In cooking, products with a high fat content are often used as enhancers of taste, for example butter, milk, cheese and other dairy products. Another use of fat in cooking is as heat conductor in frying.
They also serve as energy stores for the body. In food, there are two types of fats: saturated and unsaturated.
In the modern world, excess fatty tissue on a human is often considered an aesthetic and medical problem. For a discussion of this, see dieting and obesity. In earlier times and other societies, fat was considered aesthetically pleasing. Rembrandt's and especially Peter Paul Rubens's paintings, giving us the term Rubenesque, to describe a large woman. Fat, depending on the age and culture, is considered at once a sign of wealth, power, prestige, gluttony, and sloth.
See also: Carbohydrate; protein; lipid; biodiesel.
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