Topic 1 Important Nutrients for Humans

Topic 1

vital nutrients for humans

In order to maintain life and health, human beings must ingest food. Grains, vegetables, fruits, meat, products and other foods are the main sources of our daily nutrition. All kinds of food seem to be very different, but from a nutritional point of view, there are only six basic components, namely protein, sugar, oil, vitamin, inorganic salt and water, which are usually called the six basic nutrients

1. protein

Protein is the basic substance of cells and the main raw material for the growth of the body and repair of damaged tissues. The main components of animal muscle, skin, hair, hoof, horn and egg white are protein, and the seeds of many plants (such as soybeans and peanuts) are also rich in protein.

Proteins are extremely complex compounds composed of various amino acids (such as glycine, alanine, etc.), with relative molecular masses ranging from tens of thousands to millions. Protein is an important nutrient. Adults need to consume 60-70 g per day, and teenagers in the growth and development period need more.The protein obtained by the human body through food reacts with water in the gastrointestinal tract to form amino acids. Some of the amino acids are reconstituted into various proteins needed by the human body to maintain the growth and development of the human body and tissue renewal; the other part of the amino acids can be oxidized to produce urea, carbon dioxide and water, which are excreted from the body and release energy for human activities. The complete oxidation of each gram of protein releases about 18 kJ of energy.

Proteins in the body have multiple functions. For example, hemoglobin in the blood acts as a carrier in the process of inhaling oxygen and exhaling carbon dioxide. Hemoglobin is made up of protein and heme. In the lungs, the Fe2 + of hemoglobin in hemoglobin combines with oxygen to form oxyhemoglobin, which flows to various tissues and organs of the body with the blood, and releases oxygen for in vivo oxidation. At the same time, hemoglobin combines with carbon dioxide in the blood and carries it to the lungs for exhalation. Human respiration is such a repeated process.

Hemoglobin can also be combined with carbon monoxide, and the binding ability is very strong, about 200 to 300 times that of oxygen. Once combined, it is not easy to separate, and can no longer be combined with oxygen, and people will die of hypoxia and suffocation. This is the cause of gas poisoning. Cigarette smoke contains hundreds of toxic substances, including carbon monoxide.

Some substances, such as formaldehyde, will react with protein, destroy the structure of protein, and make it deteriorate, so formaldehyde is a serious hazard to human health. However, taking advantage of this property of formaldehyde, animal specimens can be soaked in formaldehyde solution (formalin), so that the specimens can be preserved for a long time.

2.Sugars

Carbohydrates are compounds composed of three elements, C, H, and O, and are important components of human food. Starch belongs to sugar, which mainly exists in plant seeds or tubers, such as rice, wheat, corn, potato, etc. The chemical formula of starch is (C6H10O5)n, and the relative molecular mass ranges from tens of thousands to hundreds of thousands depending on the value of n. Food starch undergoes enzyme catalysis in the human body, undergoes a series of reactions with water, and finally turns into glucose. The chemical formula of glucose is C6H12O6. Glucose is absorbed through the intestinal wall and enters the blood to become blood sugar, which provides nutrition for human tissues.

In human tissue, glucose is slowly oxidized into carbon dioxide and water under the catalysis of enzymes, and energy is released at the same time to meet the needs of body activities and maintain a constant body temperature.

In the above reaction, about 16 kJ of energy is released per gram of glucose. In the total energy supplied by human food, 60% to 70% comes from carbohydrates.

Sucrose is the sugar stored in some plants (such as sugar cane, sugar beet, etc.), and its chemical formula is Cl2H22O11 . The main component of white sugar, rock sugar and brown sugar eaten in daily life is sucrose, which is commonly used in food sweetener.

3.Grease

Fat is an important nutrient. Common oils include peanut oil, soybean oil, rapeseed oil, butter, and butter. At room temperature, vegetable fats are in a liquid state and are called oils; animal fats are in a solid state and are called fats, and the two are collectively called fats.

When each gram of fat is completely oxidized in the human body, it releases about 39 kJ of energy, which is more than twice that of sugar. It is an important energy supply substance. Under normal circumstances, people need to take in 50～60 g of fat every day, which supplies 20%～25% of the daily energy required by the human body.

General adult's internal storage accounts for about 10%-20% fat of human body mass, which is a backup energy for maintaining life activities. When a person eats a small amount of food and the energy consumed by the food is not enough to cover the energy consumed by the body, he will consume his own fat to meet the needs of the body, and the person will lose weight at this time. When the human body consumes too much oil, it is easy to cause obesity and cardiovascular and cerebrovascular diseases.

4.Vitamins

There are more than 20 kinds of vitamins, most of which cannot be synthesized in the human body and need to be ingested from food. Vitamins are required in a small amount in the human body, but they can play an important role in regulating metabolism, preventing diseases, and maintaining good health. Lack of certain vitamins can make people sick, such as lack of vitamin A, can cause night blindness; lack of vitamin C, can cause scurvy. Vegetables, fruits, seed foods, animal livers, eggs, milk, fish, cod liver oil, etc. are the main sources of vitamins for the human body.

After studying this subject, you should know

1.Basic nutrients include six categories: protein, sugar, fat, vitamin, inorganic salt and water.

2.Protein is the basic substance of cells and the main raw material for the growth of the body and repair of damaged tissues.

3.Sugars and fats are oxidized in the human body to release energy, which provides energy for body activities and maintaining a constant body temperature.

4.Vitamins can regulate metabolism, prevent disease and maintain good health.