HUMAN BIOCHEMISTRY - L. V. Kapilevich - 2016

PART 1. SPORTS BIOCHEMISTRY

BLOOD BIOCHEMISTRY

Blood is a tissue that reflects all the Biochemical characteristics of the body in both normal and pathological states. Blood analysis can help coaches adjust the training process to ensure that workloads are appropriate for the athlete's functional state.

General characteristics of Blood

Blood is a Connective Tissue circulating through Blood Vessels, consisting of two main components: plasma and formed elements. In The Human Body, blood volume averages about 5 liters. A distinction is made between circulating blood (within the vessels) and pooled (depot) blood located in the Liver, Spleen, and Skin.

The relative density of blood is 1.050-1.060, depending primarily on the erythrocyte count. The relative density of Blood Plasma is 1.025-1.034, determined by its protein concentration.

The viscosity of blood is 5 relative units, and that of plasma is 1.7-2.2 relative units, taking the viscosity of Water as 1. This is due to the presence of erythrocytes and, to a lesser extent, Plasma Proteins.

The Osmotic Pressure of blood averages 7.6 atm. It is caused by osmotically active substances dissolved in it, primarily inorganic electrolytes, and to a much lesser extent, proteins. About 60% of the osmotic pressure is generated by sodium salts (NaCl). Osmotic pressure determines the distribution of water between Tissues and Cells. The Functions of body cells can only be carried out under conditions of relative osmotic pressure stability.

The oncotic pressure of blood is the portion of osmotic pressure generated by plasma proteins. It equals 0.03-0.04 atm, or 25-30 mm Hg. Oncotic pressure is mainly due to albumins. Because of their small size and high hydrophilicity, they have a pronounced ability to attract water, thereby keeping it within the vascular bed. When blood oncotic pressure drops, water shifts from the vessels into the interstitial space, leading to tissue edema.

Acid-base balance of the blood. The active reaction of blood is determined by The ratio of hydrogen and hydroxyl ions. To determine the active reaction of blood, the pH value is used—the concentration of hydrogen ions, expressed as the negative decimal logarithm of the molar concentration of hydrogen ions. The normal pH is 7.36 (slightly alkaline reaction); arterial blood is 7.4; venous blood is 7.35. Under various physiological conditions, blood pH can range from 7.3 to 7.5. The active reaction of blood is a strict constant that ensures enzymatic activity. The extreme limits of blood pH compatible with life are 7.0-7.8. A shift in the reaction toward the acidic side is called acidosis, which is caused by an increase in hydrogen ions in the blood. A shift in the blood reaction toward the alkaline side is called alkalosis. This is associated with an increase in the concentration of hydroxyl ions OH^- and a decrease in the concentration of hydrogen ions.

Conditions for a shift in the active reaction of blood toward acidosis or alkalosis, which can alter blood pH, are always present in the human body. Acidic products are constantly formed in tissue cells. The accumulation of acidic compounds is promoted by a protein-rich diet. Conversely, increased consumption of plant-based foods introduces bases into the blood. Maintaining a constant blood pH is a vital physiological task ensured by the blood's buffer systems. The buffer systems of blood include the Hemoglobin, carbonate, phosphate, and protein buffer systems.

Buffer systems neutralize a significant portion of the acids and alkalis entering the blood, thereby preventing shifts in the active reaction of the blood. During METABOLISM, the body predominantly produces acidic products. To counteract this, the reserves of alkaline substances in the blood far exceed those of acidic substances; this constitutes the alkaline reserve of the blood.

Plasma constitutes 55-60% of blood volume, and formed elements make up 40-45%. The ratio of the volume of formed elements to the total blood volume is called the hematocrit value, or hematocrit, and normally ranges from 0.40 to 0.45.

BIOLOGICAL FUNCTIONS OF Blood

1. Respiratory function (transport of oxygen from the Lungs to all Organs and carbon dioxide from the organs to the lungs).

2. Trophic function (delivery of nutrients to organs).

3. Protective function (provision of humoral and cellular Immunity, and blood clotting during injuries).

4. Excretory function (removal and transport of Metabolic waste products to the Kidneys).

5. Homeostatic function (Maintenance of the constancy of the body's internal environment, including immune Homeostasis).

6. Transport function, due to the fact that blood contains a large amount of water, which possesses fluid properties.

Chemical composition of Blood Plasma

Blood plasma is a liquid (more precisely, colloidal) intercellular substance. It contains 90% water, about 6.6-8.5% proteins, and other organic and mineral compounds—intermediate or final metabolic products transported from one organ to another.

Blood Plasma Proteins are divided into two fractions: albumins and globulins. The ratio between albumins and globulins is called the albumin-globulin ratio, which is equal to 1.5-2.

Albumins are low-molecular-weight proteins with a molecular mass of about 70 kDa. They perform two main functions: transport, carrying various water-insoluble substances with the bloodstream, and retaining water within the vascular bed.

Globulins are high-molecular-weight proteins with a molecular mass of approximately 300 kDa. They share the same functions as albumins; in addition, they accelerate Chemical Reactions, participate in blood clotting, and play a role in immunity (protective function).

The majority of plasma proteins are synthesized in the liver. Other organic substances (aside from proteins) are generally divided into two groups: nitrogenous and non-nitrogenous.

Nitrogenous compounds are intermediate and End products of protein and NUCLEIC ACID METABOLISM. Among the intermediate products of Protein metabolism found in blood plasma are low-molecular-weight Peptides, Amino Acids, and creatine. The end products of protein metabolism are primarily urea; bilirubin, which is the end product of heme breakdown; and creatinine, the end product of creatine phosphate breakdown. Intermediate products of nucleic acid metabolism that can be detected in blood plasma include NUCLEOTIDES, nucleosides, and nitrogenous bases. The final breakdown product of Nucleic Acids is uric acid.

Additionally, blood contains non-protein nitrogenous compounds, collectively referred to as "non-protein nitrogen".

Non-nitrogenous substances in blood plasma include Introduction/36.html">CARBOHYDRATES and Lipids, as well as their intermediate metabolic products. The main carbohydrate in plasma is glucose, alongside fructose, galactose, ribose, deoxyribose, etc. Intermediate products of Carbohydrate Metabolism in plasma are represented by pyruvic and lactic acids.

Lipids are present in blood plasma as fats, Fatty acids, Phospholipids, and Cholesterol. Due to their water-insolubility, all lipids are bound to plasma proteins and are referred to as Lipoproteins. Ketone Bodies are consistently present in plasma as intermediate products of Lipid Metabolism.

Mineral Substances exist in blood plasma in the form of cations (Na⁺, К⁺, Са²⁺, Мg²⁺, etc.) and anions (Сl^-, НСO₃^-, Н₂РO₄^-, НРO₄^2-, SO4^2-, J^-, etc.). Sodium, potassium, chlorides, and bicarbonates are present in the highest concentrations in plasma. Deviations in the mineral composition of blood plasma can be observed in various diseases and during significant water loss through sweating during physical exertion.

Characteristics of Blood Cells

Erythrocytes (Red Blood Cells)

In humans and mammals, erythrocytes are anucleate cells that lost their Nucleus and most Organelles during phylo- and ontogenesis. Erythrocytes are highly differentiated post-cellular structures incapable of division.

Erythrocyte formation (erythropoiesis) takes place in the Cytology/practical/86.html">Red Bone Marrow. Their lifespan is 3–4 months, and their destruction (hemolysis) occurs in The Liver and spleen. Before entering the bloodstream, erythrocytes sequentially undergo several stages of proliferation and differentiation within the erythron—the red hematopoietic Lineage.

Typically, erythrocytes have a biconcave disc shape and contain primarily the protein hemoglobin, which binds to gases.

The primary function of erythrocytes is respiratory—The transport of oxygen and carbon dioxide. In addition, erythrocytes participate in the Transport of Amino acids, Antibodies, toxins, and A number of drugs by adsorbing them onto The surface of the Plasmalemma.

Normal erythrocyte count: in men — (4.0–5.5) • 10¹²/L, in women — (3.7–4.7) • 10¹²/L.

The erythrocyte count varies depending on age and health status. An elevated erythrocyte count is most commonly associated with tissue oxygen starvation, pulmonary diseases, or Congenital Heart defects; it can also occur due to smoking or impaired erythropoiesis caused by a tumor or cyst. A decreased erythrocyte count is a direct indicator of anemia. In advanced cases of certain anemias, variation in erythrocyte size and shape (anisopoikilocytosis) is observed, particularly in iron-deficiency anemia in pregnant women.

Sometimes a trivalent (ferric) iron atom is incorporated into the heme instead of a divalent (ferrous) one, forming methemoglobin. Methemoglobin binds oxygen so tightly that it is unable to release it to the tissues, resulting in oxygen deprivation. The formation of methemoglobin in erythrocytes can be inherited or acquired through exposure to powerful oxidizing agents such as nitrates and certain medications, including sulfonamides and local anesthetics (lidocaine).

Leukocytes (White Blood Cells)

The source of leukocytes is the red bone marrow.

Leukocytes vary in Structure and function. These cells possess a nucleus. They include granulocytes (neutrophilic, eosinophilic, basophilic), as well as lymphocytes and monocytes. Granulocytes contain granules that stain with specific Dyes and are visible under a Microscope. Neutrophil granules are gray, eosinophil granules are orange, and basophil granules are purple.

The primary function of neutrophils is to protect the body against infections. They phagocytize Bacteria, meaning they "engulf" and "digest" them. Furthermore, neutrophils can produce specialized antimicrobial substances.

Eosinophils remove excess histamine generated during allergic diseases. During helminth infections, eosinophils migrate into the intestinal lumen and disintegrate there, releasing substances that are toxic to helminths.

Basophils, together with other leukocytes, actively participate in the inflammatory response by releasing heparin, histamine, and serotonin. The latter two substances affect vascular tone and smooth Muscle contractility, which change dramatically at the site of inflammation. Heparin binds proteins that have escaped from cells into the interstitial matrix and mitigates their adverse effects on Cytoplasmic membranes.

Lymphocytes are the core component of the body's immune system. They drive The Development of specific immunity, the synthesis of protective antibodies, the lysis of foreign cells, and graft rejection reactions, while also providing immunological memory. Lymphocytes undergo differentiation in the tissues. Lymphocytes whose maturation occurs in the Thymus are called T lymphocytes (thymus-dependent). Several forms of T lymphocytes exist. Cytotoxic T cells (killer T cells) execute Cell-mediated immune responses by lysing foreign cells, infectious pathogens, tumor cells, and mutant cells. T helper cells interact with B lymphocytes to transform them into plasma cells, thereby supporting humoral immunity. Suppressor T cells inhibit excessive B lymphocyte reactions. There are also T helper and T suppressor cells that regulate cell-mediated immunity. Memory T cells store information about previously encountered Antigens. B lymphocytes (bursa-dependent) undergo differentiation in humans within the lymphoid tissue of the intestine, palatine Tonsils, and pharyngeal tonsils. B lymphocytes mediate humoral immune responses. The majority of B lymphocytes function as antibody producers. In response to antigens, and As a result of complex interactions with T Lymphocytes and monocytes, B lymphocytes transform into plasma cells. Plasma cells produce antibodies that recognize and specifically bind corresponding antigens. There are 5 main classes of antibodies, or IMMUNOGLOBULINS: IgA, IgG, IgM, IgD, and IgE. B lymphocytes also include killer cells, helper cells, suppressor cells, and immunological memory cells. Null lymphocytes (zero cells) do not undergo differentiation and serve as a reserve pool for T AND B lymphocytes.

Monocytes are immature cells. They begin to perform their primary functions upon transforming into macrophages—large, motile cells found in virtually all organs and tissues. Macrophages act as the body's cleanup crew. They "devour" bacteria and dead cells, and are capable of engulfing particles nearly equal to their own size. As previously noted, macrophages assist lymphocytes in carrying out immune responses.

In a healthy individual, the WHITE BLOOD CELL count in the blood fluctuates. It increases after strenuous physical labor, a hot bath, during Pregnancy, in The process of childbirth, and prior to menstruation, as well as following a meal. Therefore, to ensure objective test results, blood should be drawn in the morning on an empty Stomach; breakfast should be avoided, and only a Glass of water is permitted.

Normally, the leukocyte count in 1 L of blood in an adult is (4.0-9.0) • 10⁹/L.

An increase in the white blood cell count is called leukocytosis, and a decrease is called leukopenia. Leukocytosis most commonly occurs in patients with infections (Pneumonia, scarlet fever), purulent diseases (appendicitis, Peritonitis, Phlegmon), and severe Burns. Leukocytosis develops within 1-2 hours after the onset of heavy bleeding. A Gout attack may also be accompanied by leukocytosis. In certain types of leukemia, the leukocyte count increases several dozen times.

Although the invasion of microbes into the human body typically stimulates the immune system, resulting in an increased leukocyte count, some infections present the opposite picture. If the body's defenses are depleted and the immune system is unable to fight back, the leukocyte count drops. For example, leukopenia in Sepsis indicates a severe patient condition and an unfavorable prognosis. Certain infections (typhoid fever, measles, rubella, chickenpox, malaria, brucellosis, Influenza, Viral Hepatitis) suppress the immune system and can therefore be accompanied by leukopenia. A decrease in leukocytes may also occur in systemic lupus erythematosus, certain leukemias, and bone tumor metastases.

Platelets (thrombocytes)

Platelets are also formed from red bone marrow cells. They are flat, irregularly rounded cells with a diameter of 2-5 µm. Human platelets are anuclear cell fragments that are less than half the size of an erythrocyte. The normal platelet count in human blood is (180-320) • 10⁹/L. Diurnal fluctuations occur, with higher platelet counts during the day than at night. An elevated platelet count in peripheral blood is called thrombocytosis, and a decreased count is called thrombocytopenia.

The primary function of platelets is participation in hemostasis. Platelets help "repair" blood vessels by adhering to damaged walls and also participate in Blood Coagulation, which prevents bleeding and the escape of blood from the vessel.

The ability of platelets to adhere to a foreign surface (adhesion) and to clump together (aggregation) is triggered by various factors. Platelets produce and release a number of BIOLOGICALLY ACTIVE SUBSTANCES: serotonin (a substance that causes vasoconstriction and reduced blood flow), adrenaline, noradrenaline, as well as substances known as platelet clotting factors.

Self-Control Questions

1. Which structures are classified as formed elements of the blood?

2. What is blood serum?

3. List the FUNCTIONS OF BLOOD in the human body.

4. List the Main Components of blood plasma.

5. What functions are performed by blood plasma globulins?

6. What is the lifespan of erythrocytes?

7. In which organ are white blood cells produced?

8. What causes blood acidosis in athletes during muscular work?

9. What is the optimal resting blood pH in a healthy person?