Question

Explain how the bicarbonate buffer system will react to buffer a strong acid. (p. 443)

Short answer

Answer: When a strong acid is added to the bicarbonate buffer system, it reacts with the bicarbonate ion (HCO_3^-) to form carbonic acid (H_2CO_3), which then partially dissociates into a hydrogen ion (H^+) and bicarbonate ion (HCO_3^-). The carbonic anhydrase enzyme accelerates the conversion of carbonic acid (H_2CO_3) to carbon dioxide (CO_2) and water (H_2O), allowing the carbon dioxide to be exhaled by the lungs while the hydrogen ions are buffered by the bicarbonate ions, maintaining the pH balance.

Step-by-step solution

Definition of buffer system

A buffer system is a chemical system that works to resist changes in pH and maintain the acid-base balance. The bicarbonate buffer system is a key example that helps to regulate pH levels in our body, especially in blood.

Components of the bicarbonate buffer system

The bicarbonate buffer system consists of a weak acid, carbonic acid (H_2CO_3), and its conjugate base, bicarbonate ion (HCO_3^-).

Chemical reaction between a strong acid and bicarbonate buffer system

When a strong acid is added to the bicarbonate buffer system, it will react with the bicarbonate ion (HCO_3^-) present in the system to form carbonic acid (H_2CO_3). Here's the chemical reaction: Strong acid (H^+) + HCO_3^- → H_2CO_3

Dissociation of carbonic acid

Carbonic acid (H_2CO_3) is a weak acid, which means it will partially dissociate in the aqueous solution into a hydrogen ion (H^+) and a bicarbonate ion (HCO_3^-): H_2CO_3 ↔ H^+ + HCO_3^-

Role of carbonic anhydrase enzyme

The enzyme carbonic anhydrase increases the rate of conversion between carbonic acid (H_2CO_3) and carbon dioxide (CO_2) plus water (H_2O): H_2CO_3 ↔ CO_2 + H_2O The produced carbon dioxide can then be exhaled by the lungs and the hydrogen ions are buffered by the bicarbonate ions, maintaining the pH balance.

Buffering capacity

The buffering capacity of the bicarbonate buffer system lies in its ability to neutralize the excess amount of strong acids by converting them to weaker acids or carbon dioxide and water. The system can efficiently maintain the pH levels by preventing drastic changes. The bicarbonate buffer system will work effectively as long as the concentration of its components, carbonic acid, and bicarbonate ion, are maintained in a certain range, typically at a ratio of 1:20 (H_2CO_3 : HCO_3^-).

Key concepts

Buffer System Definition

In the realm of chemistry, a buffer system plays a vital role in maintaining the stability of pH in a solution. It consists of a carefully balanced mixture of a weak acid and its conjugate base — or a weak base and its conjugate acid — that work together to minimize fluctuations in pH.

A standout example of such a system is the bicarbonate buffer system. This system includes carbonic acid (a weak acid) and bicarbonate ion (its conjugate base), which coexist in a delicate equilibrium that allows the body to resist sharp changes in acidity. When you encounter a scientific or medical discussion about pH stability, you're often hearing about the impressive work of buffer systems.

Acid-Base Balance

The concept of acid-base balance is a fundamental aspect of maintaining a healthy physiological state. This balance refers to the proper level of acidity or alkalinity in our body's fluids and tissues.

Our body is continuously producing or consuming substances that can influence its internal pH. For example, during high-intensity exercise, muscles produce lactic acid, which could potentially upset this balance. The body utilizes buffer systems, like the bicarbonate buffer system, to mitigate these fluctuations and keep the pH within a very narrow, optimal range. If the pH of our blood, for instance, deviates too far from this range, it can disrupt biological processes, highlighting the importance of this delicate balance for our overall health.

Carbonic Anhydrase Enzyme

The enzyme carbonic anhydrase serves as a biochemical catalyst in the bicarbonate buffer system.

This enzyme dramatically accelerates the conversion of carbonic acid into carbon dioxide and water. This reaction is reversible and critical in controlling the levels of carbonic acid and carbon dioxide — keeping pace with the body's metabolic demands. A noteworthy feature of carbonic anhydrase is its impressive efficiency; under optimal conditions, a single molecule of this enzyme can convert over a million molecules of carbonic acid per second, which makes it one of the fastest enzymes around. Due to its involvement, the buffering action happens quickly, allowing for real-time pH regulation.

pH Regulation

pH regulation is the process by which living organisms maintain the acidity or alkalinity of their cellular and extracellular fluid within a narrow, healthy range.

The bicarbonate buffer system specifically contributes to this by regulating the pH of blood plasma. When a strong acid is introduced into this system, it is quickly neutralized. The hydrogen ions from the acid combine with the bicarbonate ions to form carbonic acid, which can then dissociate into water and carbon dioxide — the latter being expelled from the body via the lungs. This elegant system ensures that, despite continuous metabolic activities that produce acids and bases, the pH of our bodies remains stable, avoiding detrimental effects on enzyme activity, cellular functions, and overall biological processes.