Question

The most important buffer in blood consists of (1) \(\mathrm{HCl}\) and \(\mathrm{Cl}\) (2) \(\mathrm{H}_{2} \mathrm{CO}_{3}\) and \(\mathrm{HCO}_{3}\) (3) \(\mathrm{H}_{2} \mathrm{CO}_{3}\) and \(\mathrm{Cl}\) (4) \(\mathrm{HCl}\) and \(\mathrm{HCO}_{3}\)

Short answer

Option (2) H_{2}CO_{3} and HCO_{3}^{-}

Step-by-step solution

Understand the Concept of Buffers

Buffers are solutions that resist changes in pH when small amounts of acid or base are added. They typically consist of a weak acid and its conjugate base or a weak base and its conjugate acid.

Identify the Role of Buffers in Blood

In blood, buffers help maintain the pH within a narrow range. The primary buffer system in blood is the bicarbonate buffer system.

Analyze Each Option

Option (1) \(\text{HCl and Cl}\): Hydrochloric acid (HCl) is a strong acid, not typically part of buffer systems. Option (2) \(\text{H}_{2}\text{CO}_{3} \text{ and HCO}_{3}^{-}\): Carbonic acid (H_2CO_3) and bicarbonate (HCO_3^-) form a conjugate acid-base pair and make up the bicarbonate buffer system in blood. Option (3) \(\text{H}_{2}\text{CO}_{3} \text{ and Cl}\): Chloride (Cl) is not part of the main buffering system in blood. Option (4) \(\text{HCl and HCO}_{3}^{-}\): HCl, a strong acid, does not form a buffer with bicarbonate.

Select the Correct Answer

Based on the analysis, Option (2) H_{2}CO_{3} and HCO_{3}^{-} is the correct buffer system in blood.

Key concepts

bicarbonate buffer system

The bicarbonate buffer system is a crucial component in regulating the pH of our blood. This system is composed of carbonic acid (H\(_2\)CO\(_3\)) and its conjugate base, bicarbonate (HCO\(_3^-\)). These two components work together to maintain the blood's pH within the narrow range necessary for proper bodily function.

The way this works is through a dynamic equilibrium. When the pH of the blood rises, indicating a more basic environment, carbonic acid releases hydrogen ions (H\(^+\)), which helps to lower the pH. Conversely, when the pH falls, indicating a more acidic environment, bicarbonate binds with hydrogen ions, helping to raise the pH.

Through these reactions, the bicarbonate buffer system ensures our blood remains at an optimal pH, typically around 7.4.

buffers

Buffers play an essential role in maintaining the pH balance in various biological systems, including our blood. A buffer is a solution that can resist pH changes when small amounts of acids or bases are added. This quality is due to the presence of a weak acid and its conjugate base or a weak base and its conjugate acid.

In the context of blood, the bicarbonate buffer system is the primary buffer. It includes carbonic acid, a weak acid, and bicarbonate, its conjugate base. By toggling between these two forms, the buffer can neutralize added acids or bases, thus stabilizing the pH.

Without buffers, even minor fluctuations in hydrogen ion concentrations could lead to significant shifts in pH, potentially disrupting biochemical processes and endangering cellular function.

acid-base balance

Acid-base balance is vital for the body's proper functioning. This balance refers to the mechanism by which the pH levels of the body are kept within a narrow range. It is crucial because many cellular processes are pH-sensitive and only function properly within a limited pH range.

The bicarbonate buffer system is a key player in maintaining this balance. When the blood becomes too acidic (low pH), the bicarbonate can neutralize the excess H\(^+\) ions. Conversely, when the blood becomes too alkaline (high pH), carbonic acid can release H\(^+\) ions to correct the imbalance.

Maintaining this balance is critical for enzymes, proteins, and other molecules, which need a specific pH to perform their functions. Disruptions in the acid-base balance can lead to conditions such as acidosis or alkalosis, both of which pose significant health risks.

carbonic acid and bicarbonate

Carbonic acid and bicarbonate are the two main chemical components of the bicarbonate buffer system, essential for blood pH regulation. Carbonic acid (H\(_2\)CO\(_3\)) is a weak acid that forms when carbon dioxide (CO\(_2\)) dissolves in water. Bicarbonate (HCO\(_3^-\)) is its conjugate base.

In the bicarbonate buffer system, these components interact to stabilize pH. When the pH increases, signaling a more basic environment, carbonic acid dissociates into bicarbonate and H\(^+\) ions, counteracting the rise in pH. When the pH decreases, indicating a more acidic environment, bicarbonate combines with H\(^+\) ions to form carbonic acid, helping to raise the pH.

Therefore, the dynamic interplay between carbonic acid and bicarbonate helps maintain a stable and healthy pH level in the blood, contributing to overall homeostasis.