Fat is mainly digested in the upper part of the small intestine, and is decomposed into glycerol, fatty acids and so on by various enzymes and bile salts. There are two kinds of lipid absorption: triglycerides composed of medium-chain and short-chain fatty acids can be absorbed after emulsification and enter the blood through portal vein; Triglycerides composed of long-chain fatty acids combine with apolipoprotein and cholesterol to form chylomicrons, which eventually enter the blood through lymph.

(1) Energy supply: glucose is produced per gram 16 kilojoules (4 kilocalories), and carbohydrates ingested by human body are digested into glucose or other monosaccharides to participate in body metabolism.

(2) Composition of cells and tissues: Each cell contains carbohydrates, the content of which is 2%- 10%, mainly in the form of glycolipids, glycoproteins and proteoglycans, which are distributed in meninges, organelle membranes, cytoplasm and intercellular substance.

Extended data

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Lipids mainly include the following four types:

Fat: synthesized from glycerol and fatty acids. There are two sources of fatty acids in the body: one is the body itself

fat metabolism

Synthesis, second, food supply, especially some unsaturated fatty acids that the human body can't synthesize, are called essential fatty acids, such as linoleic acid and α -linolenic acid.

Phospholipids: produced by glycerol, fatty acids, phosphoric acid and nitrogen-containing compounds.

Sphingolipid: a lipid composed of sphingosine and fatty acids. Phosphoric acid is called sphingomyelin, and sugar is called sphingomyelin.

Cholesterol lipid: produced by the combination of cholesterol and fatty acids.

The main physiological functions of carbohydrates:

1, an important substance that constitutes the body;

2. store and provide heat energy;

3. Energy necessary to maintain brain function;

4. Regulating fat metabolism;

5. Provide dietary fiber;

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