Protein Chemistry. Structure, Properties, Research Methods - Shendryk A.N. 2022

Proteins of Blood and Muscle Tissues
Circulatory System
Chemical Composition of Blood

The Chemical composition of Blood normally varies very little. Proteins make up the bulk of the blood's dry residue. Any random fluctuations in blood composition are normally rapidly buffered by the Organism. Table 3.1 lists the Main Components of blood.

Blood Plasma Proteins. Proteins account for 6.5–8.5% of the 9–10% dry residue of Blood Plasma. Salting-out allows them to be divided into three groups: albumins, globulins, and fibrinogen. Their plasma levels are given in Table 3.1. Blood serum is obtained from plasma by removing fibrinogen. Blood plasma proteins are readily separated into several fractions using simple paper Electrophoresis. Their composition includes the following proteins: albumins – 54–58%, a1-globulins – 6–7%, a2-globulins – 8–9%, ß-globulins – 13–14%, y-globulins – 11–12%.

Class="center">Table 3.1 Main components of human blood and plasma

Components

Whole blood

Plasma

Water, %

75-85

90-91

Dry residue, %

15-25

9-10

Hemoglobin, g/L

130-160

-

Total protein, g/L

-

65-85

Fibrinogen, g/L

-

2-4

Globulins, g/L

-

20-30

Albumins, g/L

-

40-50

Non-protein nitrogen, mmol/L

15-25

14-21

Urea, mmol/L

3.3-6.6

3.3-6.6

Uric acid, mmol/L

0.18-0.24

0.24-0.29

Creatinine, mmol/L

0.06-0.16

0.06-0.16

Creatine, mmol/L

0.23-0.28

0.08-0.11

Amino Acid Nitrogen, mmol/L

4.3-5.7

2.9-4.3

Glucose, mmol/L

3.3-5.0

3.6-5.5

Glucosamine, mmol/L

-

3.9-5.0

Pentoses, mmol/L

-

0.13-0.26

Total Lipids, g/L

1.0-7.2

3.8-6.7

Triacylglycerols, mmol/L

1.0-2.6

1.2-2.8

Cholesterol, mmol/L

3.9-5.2

3.9-6.5

Phospholipids, g/L

-

2.2-4.0

Phosphatidylcholine, mmol/L

3.0

1.5-3.0

Ketone Bodies (calculated as acetone), mmol/L

-

0.2-0.6

Acetoacetic acid, mmol/L

-

0.05-0.19

Lactic acid, mmol/L

-

1.1-1.2

Pyruvic acid, mmol/L

-

0.07-0.14

Citric acid, mmol/L

-

0.10-0.15

a-Ketoglutaric acid, mmol/L

-

0.02-0.07

Succinic acid, mmol/L

-

0.01-0.04

Total bilirubin, µmol/L

-

4-26

Starch gel electrophoresis or Immunoelectrophoresis reveals a significantly larger number of plasma proteins. These are listed in Table 3.2.

Table 3.2 Main blood plasma proteins

Fraction

Fraction proteins

Protein content in mg/100 mL

Albumins

Prealbumin albumin

10-40


3500-4500

a1-Globulins

Glycoprotein

55-140

Retinol-binding protein antitrypsin

3-6


200-400

Fetoglobulin

= 0.001

Thyroxine-binding protein

1-2

Transcortin

3-3.5

a2-Globulins

Ceruloplasmin

15-60

Haptoglobins

380-780

Macroglobulin

150-420

Inter-a1-Trypsin inhibitor

20-70

ß-Globulins

Transferrin

200-320

Hemopexin

50-100

Microglobulin

0.2

y-Globulin

700-1500

Most blood plasma proteins have an isoelectric point (pI) of approximately 5–6, indicating that acidic Amino Acids predominate in their composition. Blood plasma proteins are synthesized primarily in Liver Cells and the reticuloendothelial system.

The physiological Functions OF BLOOD plasma proteins are as follows.

> Maintenance of colloid-osmotic (oncotic) pressure. This is achieved because the protein concentration in plasma is significantly higher than in tissue fluid. Being in a colloidal state, proteins bind water and retain it within the vascular bed.

> Several plasma proteins, including fibrinogen, serve as Key Components of the Blood Coagulation SYSTEM.

> Plasma proteins determine blood viscosity, which, as noted above, is 4–5 times greater than that of water.

> Plasma proteins participate in maintaining blood pH (buffering function).

> Transport function.

> Maintenance of the blood electrolyte balance. For instance, up to 50% of calcium in blood serum is bound to proteins. The majority of iron, magnesium, copper, and other elements are also bound to plasma proteins.

> Plasma proteins act as an amino acid reserve.

To date, about 100 different protein components of blood plasma have been investigated and described.

Paper electrophoresis of human serum clearly reveals five protein fractions: albumins, a1-, a2-, ß-, and y-globulins. Agar gel electrophoresis separates Serum proteins into 7–8 fractions, whereas starch or Polyacrylamide gel electrophoresis resolves them into 16–17 fractions. An even greater number of protein fractions (over 30) can be obtained using immunoelectrophoresis.



Last update: 06/08/2026

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