What are the categories of proteins? What are the types of proteins

Classification of proteins

There are many types of proteins, complex molecules, different functions, and most of the chemical structures are unclear, so protein classification is often classified according to their molecular shape, composition, solubility and function.

1. Classification according to molecular shape.

Globular proteins The ratio of the long and short axes of the protein molecule is less than 10. Most proteins in the biological kingdom are globular proteins. [Example].

Fibrillary proteins The ratio of the long and short axes of protein molecules is greater than 10. It is mostly the structural material of living organisms. [Example].

2. Classification according to the constituent components.

Pure protein protein contains only -amino acids in the protein fraction. Natural proteins mostly fall into this category. [Example].

Conjugated Proteins As mentioned earlier, these proteins are made by combining simple proteins with non-protein substances called prosthetic groups. According to different prosthetic groups, it can be divided into nuclear proteins, chromoproteins, glycoproteins, lipoproteins, phosphoproteins and metalloproteins. [See table].

In conjugated proteins, protein is the main component, and various prosthetic groups are the secondary components.

Example] 3. Classification by solubility.

Soluble Proteins Soluble proteins are solutions that are soluble in water, dilute neutral salts, and dilute acids.

Example] Alcohol-soluble proteins A class of proteins that are insoluble in water but soluble in 70-80% ethanol.

Example] Insoluble proteins These proteins are neither soluble in water, dilute salt solutions, nor in general organic solvents. [Example].

There are many types of proteins and complex structures, and to date there is no ideal way to classify them. For example, in terms of protein shape, they can be divided into globular protein and fibrous protein; In terms of composition, it can be divided into simple protein (the molecule only contains amino acid residues) and bound protein (in addition to amino acids, there are non-amino acid substances in the molecule, the latter is called a progroup); Simple proteins can be divided into albumin (also known as albumin), globulin, glutelin, prolamine, protamine, histone, scleroprotein, etc. according to their physical and chemical properties. Binding proteins can be divided into nucleoprotein, phosphoprotein, metalloprotein, chromoprotein, etc. according to their different cosylgroups.

According to the shape of protein molecules, they can be divided into 3 categories:

1. The molecular shape of globular protein is close to spherical, with good water solubility, many types, and can exercise a variety of biological functions.

2. The fibrous protein molecule is rod-shaped or fibrous, most of which are insoluble in water, and are important structural components of organisms, or play a protective role in organisms.

3. Membrane proteins are generally folded into a near-spherical shape and inserted into the biological membrane, and some are bound to the surface of the biological membrane through non-covalent bonds or covalent bonds. Most of the functions of biomembranes are fulfilled through membrane proteins.

Protein**

The main types of protein are meat, eggs, milk, and legumes, and generally speaking, proteins derived from animals are of high quality and contain sufficient essential amino acids.

There are about 8 kinds of essential amino acids, which cannot be synthesized by the human body and must be ingested from food, if there is a shortage of essential amino acids in the body, it will not be able to synthesize sufficient protein for the use of various tissues in the body, and other excess proteins will also be metabolized by the body and wasted, so it is important to ensure adequate intake of essential amino acids.

There are many, many more. For example, muscle protein, hemoglobin, and amino acids are arranged in different quantities, and the composition of proteins is also ever-changing.

In nutrition, food proteins are divided into three categories according to the types and quantities of amino acids contained in food proteins: 1. Complete protein: This is a class of high-quality protein. They contain a complete range of essential amino acids, in sufficient quantities, and in appropriate proportions with each other.

This type of protein not only supports human health, but also promotes growth and development. The proteins in milk, eggs, fish, and meat are all complete proteins. 2. Although semi-complete proteins contain a complete range of amino acids, the number of some amino acids cannot meet the needs of the human body.

They can sustain life, but they do not promote growth and development. For example, gliadin in wheat is a semi-complete protein with very little lysine. One or several amino acids contained in food that are different from what the body needs are called limiting amino acids.

Cereal proteins tend to contain less lysine, so their limiting amino acid is lysine. 3. Incomplete proteins This type of protein cannot provide all the essential amino acids needed by the human body, and they alone can neither promote growth and development, nor can they sustain life. For example, the collagen in the skin of meat is an incomplete protein.

The classification of protein can be divided into animal protein and plant protein; Nutritionally, it can be divided into complete protein, semi-complete protein, and incomplete protein.

1.**Classify.

1) Animal protein: mainly includes some animal meat (such as beef, pork, meat, chicken, etc.) and eggs (eggs, duck eggs, quail eggs, etc.), dairy products (milk, goat milk, etc.), etc., containing more amino acids, rich in nutrients, easy to absorb.

2.Classification of Nutrition.

1) There are more varieties and quantities of amino acids contained in complete proteins, such as proteins in dairy products, animal liver, and other foods.

2) Incomplete protein contains relatively few types and quantities of amino acids, such as animal gelatin and corn gum protein.

3) There are also many types of amino acids in semi-complete proteins, but they are relatively insufficient, such as the ingredients in gliadin.

Proteins include animal protein and plant protein.

1. Animal protein is mainly used in poultry or livestock or fish, etc., animal meat, eggs, milk and other foods, animal protein contains more essential amino acids, so the nutritional value is relatively high.

2. Vegetable protein mainly comes from legumes or cereals, etc., plant protein does not contain cholesterol and saturated fatty acids, and can also provide more dietary fiber and unsaturated fatty acids. The seeds of some plants, such as rice, soybeans, wheat or root plants, will contain different amounts of different types of plant protein.

Proteins are distinguished by function, including structural proteins (the structure of cellular organisms) and functional egg structures (which assume certain functions). Animal protein and plant protein are distinguished by food**.