Biochemical Foundations of Human Vital Activity - Volkov, N. I., & Nesen, E. N. 2000

Biochemical Foundations of Human Vital Activity
Acid-Base Balance of the Body
Buffer systems and their role in maintaining stable environmental pH

Alteration of the acid-base balance can lead to pathological conditions or even death. Therefore, the body possesses special systems that prevent fluctuations in the pH of Blood and other biological fluids caused by the accumulation of acidic and alkaline products or excessive Water intake. This role is performed by specific physiological systems (respiratory and excretory), as well as by buffer systems. The latter react very rapidly (within seconds) to changes in H⁺ and OH^- concentrations in aqueous environments, serving as prompt regulators of the acid-base balance in body Tissues.

Buffer systems are a mixture of a weak acid and its soluble salt, two salts, or Proteins capable of preventing Changes in the pH of aqueous media. The action of buffer systems aims to bind excess H⁺ or OH^- ions in the medium and maintain a constant pH. This interaction yields weakly dissociated substances or water.

The primary Blood Buffer Systems include the bicarbonate, protein (Hemoglobin), and phosphate buffers. Acetate and ammonium buffer systems are also present. The Cell/6.html">Chemical Components of these buffer systems, their dissociation, and their most effective pH maintenance ranges are presented in Table 6.

The efficacy of buffer systems is limited by their buffer capacity, which is measured by The amount of acid or base that must be added to a buffer solution to alter its pH by one unit per 1 liter of solution. When the reserves of substances possessing buffering action are depleted, the active reaction of the body's internal environment changes. The total amount of substances capable of binding acidic products and counteracting an increase in H⁺ ion concentration in the medium is termed the alkaline buffer reserve of the body. It is determined principally by bicarbonate reserves. The total buffer capacity of these systems averages 28 mEq of H⁺ per liter of blood. The generation of such an amount of H⁺ shifts the pH from 7.4 to 7.0. The capacity of athletes to perform work under anaerobic conditions, which generate large amounts of acidic metabolic products, depends directly on their alkaline buffer reserves. The alkaline reserve of the blood increases with an excessive intake of dietary alkaline components, such as NaHCO₃, or the administration of special salt mixtures.

Class="center">TABLE 6 Body buffer systems, their dissociation, and pH maintenance ranges

The buffering capacity of the body's systems increases during anaerobic exercise. During aerobic exercise, the buffer capacity of these systems remains practically unchanged. Thanks to an enhanced buffering capacity, the H⁺ concentration is maintained at a stable level even during submaximal physical exertion, allowing Muscles to perform work without rapid fatigue.

The Mechanism of buffer systems can be illustrated using the bicarbonate system. When acidic products enter the bloodstream, H⁺ protons interact with HCO₃^- ions derived from the dissociation of NaHCO₃, the alkaline component of the system. This leads to The formation of excess carbonic acid (H₂СО₃). Its concentration is subsequently reduced by accelerating its breakdown into CO₂ and H₂O. Carbon dioxide is eliminated from the body via the Lungs during Respiration, while the plasma bicarbonate system is restored:

When alkaline components enter the blood, hydroxyl groups (OH^-) are bound by weak carbonic acid, yielding water and bicarbonate ions:

The Kidneys excrete excess basic salts and restore the bicarbonate system.

Review Questions

1. What is the internal environment of the body, and what are its properties?

2. Which systems are involved in maintaining the constancy of The chemical composition of the body's internal environment?

3. What is diffusion, and what is its biological role? Provide a specific example.

4. What is meant by osmosis? How does it affect erythrocyte function during dehydration?

5. Explain The Role of Active Transport processes in The Human Body.

6. What transport mechanisms ensure hormone secretion and the neutralization of Bacteria and microorganisms?

7. What determines the active reaction of the environment or the acid-base state?

8. What is pH? What is its range of variation?

9. Indicate the pH values corresponding to acidic, neutral, and alkaline environments.

10. What are the pH values of blood, urine, and gastric juice?

11. Which biological processes are affected by changes in pH?

12. How does the body's acid-base balance change during physical exertion?

13. What is acidosis and how does it affect physical performance?

14. Which systems are involved in maintaining acid-base balance in the body?

15. What body buffer systems do you know and what is their MECHANISM OF ACTION?

16. How is a highly trained body able to sustain maximal physical effort for a longer period?