In the process of human life activities, all life activities need energy, such as the synthetic reaction of material metabolism, muscle contraction, gland secretion and so on. And these energies mainly come from food. Nutrients contained in animal and plant foods can be divided into five categories: carbohydrates, lipids, protein, minerals and vitamins, and water is six categories. Among them, carbohydrates, fats and protein can release energy through in vivo oxidation. These three are collectively referred to as "productivity nutrients" or "heat source substances"

Card is short for calorie. Card is an energy unit, which is still widely used in nutrition measurement and fitness manual. The international standard unit of energy is joule.

Lipid is a general term for oil, fat and lipid. The fat in food is mainly fat. Generally speaking, liquid at room temperature is called oil, and solid at room temperature is called fat. Fat is composed of three elements, C, H and O. Fat is a triacylglyceride composed of glycerol and fatty acids, in which the molecule of glycerol is relatively simple, but the types and lengths of fatty acids are different. Fatty acids are divided into three categories: saturated fatty acids, monounsaturated fatty acids and polyunsaturated fatty acids. Fat is soluble in most organic solvents, but insoluble in water. Glycerol C3H5(OOCR) 3 is one or more fatty acids.

Extended data

Lipid classification

Fat is a triglyceride synthesized by glycerol and three molecular fatty acids.

Sphingolipid: cerebroside, ganglioside.

Lipoprotein: chylomicron, very low density lipoprotein, low density lipoprotein and high density lipoprotein.

Steroids: cholesterol, ergosterol, corticosteroids, cholic acid, vitamin D, androgen, estrogen and progesterone.

In nature, the most abundant is mixed triglyceride, which accounts for 98% of the fat in food and more than 28% in the body. All cells contain phospholipids, which are structures in cell membrane and blood, and are very high in brain, nerve and liver. Lecithin is one of the most abundant phospholipids in diet and body. Four kinds of lipoproteins are the main means to transport lipids in the blood.

Refer to Baidu Encyclopedia-Fat

Baidu encyclopedia-energy