Question

Effect of Holding One's Breath on Blood pH The pH of the extracellular fluid is buffered by the bicarbonate/carbonic acid system. Holding your breath can increase the concentration of \(\mathrm{CO}_{2}(\mathrm{aq})\) in the blood. What effect might this have on the pH of the extracellular fluid? Explain the effect on \(\mathrm{pH}\) by writing the relevant equilibrium equation(s) for this buffer system.

Short answer

Holding breath increases CO₂, shifts equilibrium, increases H⁺, decreases pH.

Step-by-step solution

Identify the Buffer System

The bicarbonate/carbonic acid buffer system involves the equilibrium between carbon dioxide (\(\mathrm{CO}_2\)), carbonic acid (\(\mathrm{H}_2\mathrm{CO}_3\)), bicarbonate ion (\(\mathrm{HCO}_3^-\)), and hydrogen ion (\(\mathrm{H}^+\)). This can be represented by the following equation:\[\mathrm{CO}_2 + \mathrm{H}_2O \rightleftharpoons \mathrm{H}_2\mathrm{CO}_3 \rightleftharpoons \mathrm{H}^+ + \mathrm{HCO}_3^-\]

Understand the Effect of Holding Breath

When you hold your breath, the concentration of \(\mathrm{CO}_2\) in the blood increases. According to Le Chatelier's Principle, the equilibrium shifts to the right to form more \(\mathrm{H}_2\mathrm{CO}_3\) and subsequently more \(\mathrm{H}^+\) ions.

Explain the pH Change

As the concentration of \(\mathrm{H}^+\) ions increases, the pH of the extracellular fluid decreases, making the fluid more acidic. A decrease in pH corresponds to an increase in hydrogen ion concentration.

Conclude with the Effect on the Human Body

The increase in \(\mathrm{CO}_2\) due to holding one's breath results in the blood becoming more acidic, which may affect various physiological processes, potentially leading to respiratory acidosis if sustained.

Key concepts

Carbon Dioxide and Blood pH

The concentration of carbon dioxide (\( \mathrm{CO}_2 \) ) in the blood plays a significant role in maintaining the body's pH balance. This is mainly because of its involvement in the bicarbonate buffer system. When you breathe, oxygen is taken in and carbon dioxide is expelled. By holding your breath, \( \mathrm{CO}_2 \) begins to accumulate in the bloodstream.
As the level of \( \mathrm{CO}_2 \) rises, it reacts with water to form carbonic acid (\( \mathrm{H}_2\mathrm{CO}_3 \)). This process is reversible and forms part of the equilibrium in the bicarbonate buffer system. The raised levels of carbonic acid eventually dissociate to release hydrogen ions (\( \mathrm{H}^+ \)).
Increased hydrogen ions in the blood lead to a decrease in pH, making the blood more acidic. This delicate balance is crucial to keep various bodily functions running smoothly.

Le Chatelier's Principle

Le Chatelier's Principle plays a crucial role in understanding how chemical equilibria respond to changes. This principle states that if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change.
In the context of our bicarbonate buffer system, if we introduce more \( \mathrm{CO}_2 \) by holding our breath, the equilibrium will shift to balance this increase. The system compensates by moving the equilibrium position to the right:

• Forming more carbonic acid (\( \mathrm{H}_2\mathrm{CO}_3 \))
• Increasing the concentration of hydrogen ions (\( \mathrm{H}^+ \))

This shift results in a lower pH, illustrating how the body employs chemical principles to maintain homeostasis.

Respiratory Acidosis

Respiratory acidosis occurs when the blood becomes too acidic due to an excessive amount of carbon dioxide. This is a potential consequence of extended periods of holding one's breath. The body's buffering systems, like the bicarbonate buffer system, work to mitigate the changes in blood pH, but they have their limits.
When \( \mathrm{CO}_2 \) levels continue to rise, the increase in hydrogen ions results in lower blood pH.
If this state persists without correction, the body might experience negative physiological impacts, such as compromised enzyme function and impaired cellular activities.
Understanding respiratory acidosis underscores the importance of adequate respiration to prevent shifts in blood chemistry that could disrupt bodily functions.