If some salt is added to egg whites, will its biological activity change?

Adding table salt to egg whites creates white flocculents! Because salting out of proteins occurs in egg whites. When inorganic salts are added to egg whites, the solubility of protein colloids decreases, and the white flocculent is the precipitated protein.

The process is reversible, the protein is not denatured, and the white flocculent is dissolved when water is added.

If strong acids, strong alkalis, heavy metal salts, etc. are added, protein denaturation will occur. The process is irreversible, and if a precipitate is generated, it is insoluble with water.

The denaturation of proteins is the effect of proteins being affected by physical or chemical factors that change the internal structure and properties of their molecules. Protein is still protein after denaturation, such as heating eggs can denature the protein of eggs, but its composition is still protein, but the nutritional value has changed.

Egg whites can be seen as a protein solution, and the solubility of protein in water will decrease as the concentration of sodium chloride, that is, table salt, in the solution increases, and this process is called protein salting-out. Salting out is a reversible process, meaning that the protein is not denatured during this process and will re-dissolve when water is added.

Hello. Yes. And the use of egg white to compress the face, mainly has the following effects:

Clause. 1. Shrink pores.

For oily**, egg white compress can shrink pores and make the skin cleaner and firmer; Neutral** people are better to add a few drops of honey to enhance the moisturizing effect.

Clause. 2. Wrinkle removal.

The main substances in egg white are protein and simple sugar, which is an important nutrient, often use egg white to compress the face, can achieve an effective wrinkle removal effect, dry skin should be used with caution, to avoid getting drier and drier.

Clause. 3. Oil control.

Egg white is rich in protein, methionine and vitamins, phosphorus, iron, potassium, magnesium, sodium, silicon and other minerals and a variety of nutrients, because egg white has an astringent effect, can effectively control the oiliness of the face, which is also the reason why many people with dry skin are not suitable for using egg white** on the face.

Clause. Fourth, acne.

Egg white can effectively inhibit the oiliness, acne is caused by excessive oil secretion, so effectively inhibiting the oiliness can effectively remove acne, acne in addition to egg white, we must also quit spicy food, eat less sweets, and develop good work and rest habits.

Clause. 5. Exfoliate.

Egg white is a natural scrub that can remove exfoliation on the face, but you can't often use this method to exfoliate the face, and you can only use egg white to exfoliate your face twice a week to avoid damage to the stratum corneum and cause dryness.

7 The structure and properties of proteins are relatively stable, but there are also many factors that can lead to protein denaturation and inactivation Which of the following phenomena is protein denaturation? （

A little salt is added to the egg white, and a white flocculent precipitate can be observed.

Hard-boiled eggs cannot be restored to their original shape.

The hair burns and emits a burnt smell.

Egg whites turn yellow when exposed to concentrated nitric acid.

Soy milk is heated and gypsum is added to make tofu

a． ①b． ①c． ②d． ①

Answers to test questions. Analysis Protein denaturation refers to the change of protein properties and the loss of biological activity under the action of certain physical and chemical factors, this phenomenon is called protein denaturation

Answer: Adding a little salt to the egg white can observe the white flocculent precipitation, which belongs to the salting out phenomenon, and the structure and activity of the protein are not lost at this time, wrong;

Hard-boiled eggs are heated at high temperatures and lose their structure and activity, correctly;

Hair burning is the loss of structure and activity of proteins after they are burned at high temperatures, correctly;

Egg whites turn yellow when exposed to concentrated nitric acid, and it is a chemical factor that denatures it, right;

The structure of the soybean milk is destroyed during the heating process, which is denaturation, correct

Therefore, this question is not very difficult, it examines the denaturation of proteins, and you can answer this question correctly by understanding the denaturation of proteins and the factors of denaturation

The formation of a cyclic peptide from n amino acids means: Number of peptide bonds formed = number of water molecules lost = n In addition to considering the relative mass of the dehydrated molecules, sometimes it is also necessary to consider the reduction of the relative molecular mass caused by the formation of other chemical bonds: A disulfide bond is formed, two hydrogen atoms are removed, and the relative molecular mass is reduced by 2

Exercise 6 (2013) A protein is composed of 124 amino acids, of which 8 are —sh, and when the peptide chain forms a spatial structure (as shown in the figure), 4 disulfide bonds (—s—s—) are generated, and if the average molecular weight of amino acids is 125, the molecular weight of the protein is ( )a 13278 b 13286 c 13294 d 15500 -s-s- -s-s- -s-s- -s-s- -s-s- Molecular weight of amino acids - the relative molecular weight of the water molecule removed (number of peptide bonds x18) - the relative atomic mass of the removed hydrogen atom (number of disulfide bonds removed x2) 124x125-(124-1)x18-4x2 = 13278 7. Among the following structures, the peptide bonds are () b-co-nh- 8. A protein is composed of 4 peptide chains and contains a total of 109 peptide bonds, then the number of amino acids involved in the synthesis of this protein is () 9. The type, number, order and spatial structure of amino acids There are three kinds of amino acids, A, B and C, and when the number of each amino acid is unlimited, the number of types of tripeptide compounds that can be formed is () What is the reason for the diversity of proteins? The type, number, order of amino acids and the spatial structure of proteins b a d 3. Hierarchical structure of proteins The types of amino acids are different; The number of amino acids varies; The amino acids are arranged in different order; The spatial structure of peptide chains is very different Protein structure diversity Protein functional diversity Thermal denaturation The spatial structure of protein molecules is unstable and will change with the increase of temperature, and once the spatial structure is irreversibly changed, it will lose its biological activity.

Add some table salt to the egg white, and you will see white flocculents, which are proteins precipitated under the action of table salt. When diluted with water, you will notice that the flocculent disappears.

The method of increasing the density of the solution can be solved by adding solutes, such as sugar, salt (all salts in chemistry), etc., which are all physical methods.

Mass-volume concentration: The concentration expressed in terms of the mass of solute contained in a unit volume (1 cubic meter or 1 liter) of solution is called mass-volume concentration, and is expressed by the symbol g m or mg l. For example, if 1 liter of chromium-containing wastewater contains 2 milligrams of hexavalent chromium, then the concentration of hexavalent chromium is 2 milligrams of liters (mg l) mass - volume concentration = mass of solute (grams or milligrams) volume of the solution (cubic meters or liters).

Let the density of the water increase, the density of salt water is greater than that of water. So by adding salt, sugar, or something else that makes the aqueous solution denser than the egg, you can make the egg float in the water.

Sugar and salt are readily available in everyday life and are harmless to people. Take a slightly larger transparent container, add water, and put in the eggs.

Slowly add the salt, and when a certain amount of salt is added, you will see the eggs slowly rise. Finally can surface. This process is illustrated by a synthetic **. From left to right, unsalted, moderately salted, and plenty of salt.

The methods mentioned upstairs are all ways to increase the density of the solution, which can be solved by adding solutes, such as sugar, salt (all salts in chemistry), etc., which are all physical methods.

Another method is the chemical method: add a small amount of hydrochloric acid or a large amount of vinegar to the water, and then put the egg in it, and it will float after a while, the principle is that the acid will react with the eggshell (calcium) chemically, producing a large number of bubbles attached to the surface of the egg, which will increase the buoyancy, and the egg will float.

Eggs marinated in salt water, after a period of time, the eggs will become salty, which belongs to the diffusion phenomenon of molecules, and the diffusion phenomenon indicates that the molecules are constantly doing irregular movements;

When boiling tea eggs, the eggshell is dyed brown quickly, but the egg is not dyed so quickly when you put it in cold water, because the speed of molecular movement is related to temperature

So the answer is: the molecules are constantly moving irregularly; The speed of molecular movement is related to temperature

The egg will float upward, because the density of the salt water is greater than the original water, and the density also increases its buoyancy, causing the eggs that had sunk at the bottom of the cup to float to the surface.

f (buoyancy) = p (density of liquid) * newton kg * v (volume of liquid discharged by the object, i.e. volume of the object).

a salt water does not denature proteins, so a is wrong;

b Heating can kill bacteria and parasites, and make the protein loose and easy to be digested and absorbed, so B is wrong;

c The protein solution is colloidal and has a Tyndall effect, so c is correct;

d The constituent elements of proteins (amino acids) are composed of C, H, O, N, and some also contain P and S, so D is wrong

Therefore, C

The former floats, the latter sinks

1. Hard-boiled eggs in large amounts of brine will float – because when the concentration of brine is large enough, they may float (the density of the water increases).

Second, the boiled eggs put in a small amount of salt water, because the concentration is not enough (the density of the water cannot reach), so the eggs will not float, but sink!