We know that there are six essential nutrients for people's lives: water, inorganic salts, vitamins, carbohydrates, fat and protein. The first three are inorganic nutrients, and the last three are organic nutrients.

The first three nutrients were introduced before. As a college student who majors in bio-chemistry, today, let me introduce the last three inorganic nutrients for you. So let's start.

Sugars are the direct source of human energy. Sugars are divided into Monosaccharide, disaccharides and polysaccharides. Monosaccharide are saccharides that can no longer be hydrolyzed. They are the basic units of molecules that make up various disaccharides and polysaccharides. Here we will not discuss Amino Sugars about DNA and RNA, but only hex-carbohydrates. Monosaccharide are the basic constituents of sugars. Their chemical expression is C-6-H12-O6. Because their chemical formula is like the combination of carbon and water, they are also called carbohydrates. Monosaccharide are biologically available carbohydrates, which can be completely converted into energy required by people through TCA cycle, namely ATP. According to the different chemical chains, it can be divided into glucose, fructose, and most of the human body uses glucose.

Disaccharides are formed by the combination of two Monosaccharide, and two monosaccharide can be obtained by hydrolysis of disaccharides. Sugars in nature exist in the form of polysaccharides. Polysaccharide is a glycoside-bonded sugar chain, composed of at least 10 Monosaccharide, which can be expressed by the general formula (C6H10O5) n. Polysaccharides consisting of the same Monosaccharide are called homopoly-saccharides, such as starch, cellulose and glycogen; polysaccharides are not pure chemicals, but mixtures of substances with different degrees of polymerization. Polysaccharides are generally insoluble in water, no sweetness, no crystallization, no reduction and rotation. Polysaccharides are also glycosides, so they can be hydrolyzed. In the process of hydrolysis, a series of intermediate products are often produced, and ultimately Monosaccharide are obtained by complete hydrolysis. The introduction of polysaccharides can help us understand glycan analysis.

Fat is another kind of energy storage organic matter. Its chemical composition is composed of three elements: C, H and O. Fat is a Triglyceride composed of glycerol and Fatty Acids. The molecule of glycerol is relatively simple, but the type and length of fatty acids are different. Fatty acids fall into three categories: Straight Chain Fatty Acids, Branched Chain Fatty Acids and Saturated Fatty Acids. Fat is soluble in most organic solvents, but not in water. Glycerol C3H5 (OOCR) 3 is one or more fatty acids.

Lipids in the human body are divided into two parts: fat and lipid. Fat, also known as true fat, neutral fat and triesters, is a combination of glycerol and trimolecular fatty acids. Fats include unsaturated and saturated fats. Animal fats are mostly saturated fatty acids, which are solid at room temperature. On the contrary, vegetable oils contain more unsaturated fatty acids and are liquid at room temperature. Lipids refer to cholesterol, cephalin, lecithin and so on. Its functions include: fat is a good energy storage material in cells, mainly providing heat energy; protecting viscera, maintaining body temperature; assisting in the absorption of fat-soluble vitamins; participating in various aspects of metabolic activities of the body and so on.

There are two sources of fat:

Animal origin: Fats stored in animals, such as lard, butter, lamb oil, fish oil, bone marrow, fat, cod liver oil, etc. Fat in animal milk, such as butter.
Botanical sources: Botanical sources of fat are mainly extracted from the fruits of plants, such as sesame, sunflower seeds, tea plants, walnuts, pine seeds, soybeans and so on. The main sources of fat are cooking oils and oils contained in food itself. Fruit kernels have the highest fat content, and meat is in the middle, while rice, noodles, vegetables and fruits have little fat content.