molecular composition of protein

Biochemistry, Human Health 9th Edition, introduces the definition of protein, Functions of proteins, classification of amino acids, Physical and chemical properties of amino acids, etc.

Edited at 2024-02-08 16:38:01

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molecular composition of protein

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Outline

molecular composition of protein

protein definition

Protein is a high molecular nitrogen-containing compound composed of many amino acids linked by peptide bonds.

protein function

fuel

Energy Supply

Material

constitute

seasoning

adjust

Composition elements: C, H, O, N, S

S is a special element of protein

The nitrogen content of protein is close to 16%

Nitrogen determination method: nitrogen content per gram of sample × 6.25 × 100 = protein content in 100g sample

L-alpha-amino acid is the basic structural unit of protein

All amino acids except glycine are chiral amino acids

Classification of amino acids

Nonpolar aliphatic amino acids (7)

Gan, acrylic, valerian, bright, different bright, preserved, methyl sulfide (egg)

Polar neutral amino acids (5)

Silk, cysteine, asparagine, glutamine, soda

Aromatic amino acids (3)

Styrene, acrylic, cheese, color

Acidic Amino Acids (2)

Tiandong, Gu

Basic amino acids (3)

Jing, group, lai

Physicochemical properties of amino acids

1. Nature of sexual dissociation

Isoelectric point: In a solution of a certain pH, the tendency and degree of amino acid dissociation into cations and anions are equal and become zwitterive ions, which are electrically neutral. The pH of the solution at this time is called the isoelectric point of the amino acid.

2. Amino acids containing conjugated double bonds have UV absorption properties

UV absorption of tryptophan and tyrosine containing conjugated double bonds

3. The reaction between amino acids and ninhydrin produces a blue-purple substance

The maximum absorption peak of this blue-violet compound is 570nm

Amino acids are linked through peptide chains to form proteins or peptides

Oligopeptides and polypeptides

Peptides composed of 2 to 20 amino acids linked together are called oligopeptides

amino acid residue

The amino acid molecules in the peptide chain have incomplete groups due to dehydration and condensation and are called amino acid residues.

Bioactive peptides have physiological activity and diversity

(Two cysteines can form a disulfide bond through dehydrogenation to form cystine)