How to determine the relative molecular mass of biological peptides or pros?

Because each amino acid has a -NH2 and a -COOH in the position of the two amino acids, when the two amino acids form a dipeptide, the -NH2 of the former amino acid and the -COOH of the latter amino acid combine to form a dipeptide and get rid of a molecule of H2O

In the same way, the formation of tripeptides requires the removal of 2 molecules of water.

To form an N-peptide, it is necessary to detach (N-1) molecular water.

So the molecular mass of the polypeptide or pro is.

The sum of the molecular masses of amino acids - the molecular mass of the dewatered water.

A amino acid, the relative molecular weight does not exceed 200, after analysis, it can be seen that the amino acid contains four elements: c, h, o, n, of which the mass fraction of nitrogen is and the mass fraction of oxygen is, fill in the blank by calculation:

1。How many -NH2 are in the molecule of this amino acidHow many - cooh?

2。What is the relative molecular weight (rounded value) of this amino acid?

I don't know anything else.

Peptide is a compound formed by amino acids linked together by peptide chains, and it is also an intermediate product of protein hydrolysis.

Compounds formed by the dehydration and condensation of two amino acid molecules are called dipeptides, and the same is true for tripeptides, tetrapeptides, pentapeptides, etc. Compounds that are usually formed by dehydration and condensation of 10 100 amino acid molecules are called polypeptides. They have a molecular weight of less than 10,000 Da (Dalton) and are not precipitated by trichloroacetic acid and ammonium sulfate through semi-permeable membranes.

There is also literature that calls peptides composed of 2 10 amino acids oligopeptides (small molecule peptides); 10 peptides composed of 50 amino acids are called polypeptides; Peptides that are made up of more than 50 amino acids are called proteins.

How to understand? Add up the mass of all the amino acids that make up the peptide. Then subtract the mass of the water molecules that are removed. What's so hard to understand..! I don't understand!

When amino acids form proteins or peptides, they are not dehydrated and condensed, the carboxyl group of amino acid A and the amino group of amino acid B are dehydrated and condensed to form dipeptides, in which the loss of a molecule of water is the relative molecular weight of the original A + the relative molecular weight of B -18 (the relative molecular weight of a part of water). And so on, 3 condensations are less than 2 molecules, and n are less (n-1) water. It's a chain.

The two chains, etc., should be counted separately and then added.

Relative molecular weight of polypeptides, number of amino acids, average relative molecular weight of amino acids (number of amino acids, number of peptide chains).

Formula: number of amino acids = number of peptide chains + number of peptide bonds.

Number of peptide bonds = number of water molecules removed.

Relative molecular weight of protein = number of amino acids * average relative molecular weight of amino acids - total relative molecular weight of dehydrated molecules.

Generally, it is ...... with formulas

Let's give me an example question

20 kinds of amino acids The average relative molecular weight is 128, the relative molecular weight of protein is 128, the relative molecular weight of protein is 10228, and the total amount of water removed when forming protein molecules is 1548, which is the number of peptide chains that make up proteins.

Start calculating. The total amount of dehydrated water was 1548, and the number of dehydrated water = 1548 18 = 86 peptide bonds = 86.

Relative molecular weight of protein = number of amino acids * average relative molecular weight of amino acids - total relative molecular weight of dehydrated molecules.

Algebra 10228 = number of amino acids * 128-1548 number of amino acids = 92.

Number of peptide chains = number of amino acids - number of peptide bonds = 92-86 = 6

Number of amino acids = number of peptides + number of peptide chains Number of peptide bonds = number of dehydrated molecules If a polypeptide chain is composed of n amino acids, the average weight of each amino acid m is so much peptide weight: nm-18 (n-1).

The molecular weight calculation method of polypeptide is as follows; According to the following formula; The number of amino acids is equal to the number of peptide chains plus the number of peptide bonds; The number of peptide bonds is equal to the number of water molecules removed; The relative molecular weight of the protein is equal to the number of amino acids multiplied by the average relative molecular weight of the amino acids minus the total relative molecular weight of the molecules minus the waterless molecules; Perform calculations to find the molecular weight of the peptide.

Knowing the structural composition, the molecular formula can be calculated.

Or you can't just measure.

If a polypeptide chain is known to be composed of n amino acids, its relative molecular mass m n a (n 1) 18

Because: assuming that the coefficients of the equation are 1, and the amount of substances of each substance is measured in moles, then n amino acids form a polypeptide with a total of (n 1) peptide bonds, and each peptide bond formed will generate one mole of water, and the relative molecular mass of water is 18 grams per mole.

The simple understanding is "subtract the water generated from the total amount".

Amino acid. The average phase of the suspect is the number of amino acids in the number of amino acids - (peptide bond number 18).

The average molecular weight of the amino acids, multiplied by the number of amino acids minus the number of dehydrations multiplied by 18.

Relative molecular weight of amino acids - Loss of the relative molecular weight of water molecules.

Amino acids mean relative molecular weight of ammonia number - (peptide bond number 18).

It is the quality of amino acids.

The simplest and most straightforward thing is to add the relative atomic weights of each atom in the polypeptide molecule and sum it up like the ordinary chemical substance you learned; In biology, it is calculated indirectly, and the relative molecular weight of the constituent amino acid molecules is summed and the relative molecular weight of all the water removed is subtracted. A peptide molecule is also a molecule, which can be understood as an ordinary chemical.

1.Find the number of peptide bonds and the number of dehydration: the number of peptide bonds = the number of dehydrations = m-n. It is because of the water that is removed that the peptide bonds are formed.

2.Calculation of the molecular weight of the polypeptide: according to the conservation of molecular weight, let the average molecular weight of amino acids be a, and the molecular weight of peptides =

ma-18(m_n)

3.There is also a category of topics that are calculated according to the conservation of atoms, such as the maximum number of peptide bonds, etc., which are generally calculated according to the number of n atoms.

4.Calculation of at least amino carboxyl base for the purpose of the project; A peptide chain has at least one free amino group and one free carboxyl group, and most of them are in the R group.

I've summarized a lot, it's too troublesome to enter, just these, Haihan!

When there are no cyclic peptide chains in the formed protein, the identity formula [number of amino acids = number of peptide bonds + number of peptide chains] number of peptide bonds = number of water molecules removed from the synthetic protein = number of water molecules required for protein hydrolysis m amino acids, n peptide chains can form m-n peptide bonds, m-n water m amino acids can be removed, z cyclic peptide chains can form m peptide bonds, m water m amino acids are removed, n peptide chains are removed, and when there are z cyclic peptide chains, there are m-(n-z) peptide bonds, and m-(n-z) water is removed.

Peptide mass = average amino acid mass * number of amino acids - mass of water * number of peptide bonds.

Number of peptide bonds = number of amino acids - number of strips of peptide chain.

Compounds that are joined together by amino acids by peptide bonds are called peptides. A peptide that is made up of two amino acid molecules is called a dipeptide, and a peptide that is condensed into three amino acids is called a tripeptide. Peptides synthesized with more than 10 amino acids are called polypeptides.

It is generally believed that polypeptides containing more than 40 amino acids should be called proteins.

Number of peptide bonds = number of amino acids in the peptide chain - 1

Number of synthetic protein dehydration = number of peptide bonds = number of amino acids in the peptide chain -1

Give it points

1.Number of amino acids = number of peptide bonds + number of peptide chains.

2.Number of peptide bonds = number of water molecules removed = number of amino acids - number of peptide chains3Protein relative molecular weight = number of amino acids Average relative molecular weight of amino acids - number of water molecules removed 18

4.In the case of cyclic proteins: number of amino acids = number of peptide bonds = number of water molecules removed.