Acid-Base Balance and Buffering in Human Physiology

Q10. How does the equation below shift when the plasma CO2 concentration rises?

Background

Topic: Acid-Base Balance and Buffering

This question tests your understanding of the carbonic acid-bicarbonate buffer system and how changes in CO2 levels affect acid-base equilibrium in the body.

Key Terms and Formulas

• CO2: Carbon dioxide, a waste product of cellular respiration.

• H2O: Water.

• H2CO3: Carbonic acid, formed from CO2 and water.

• H+: Hydrogen ion, contributes to acidity.

• HCO3-: Bicarbonate ion, acts as a buffer.

• Carbonic anhydrase: Enzyme that catalyzes the conversion between CO2 and H2CO3.

Key formula:

$\text{CO}_2 + \text{H}_2\text{O} \xleftrightarrow{\text{carbonic anhydrase}} \text{H}_2\text{CO}_3 \xleftrightarrow{} \text{H}^+ + \text{HCO}_3^-$

Step-by-Step Guidance

1. Recognize that an increase in plasma CO2 means more substrate is available for the reaction.

2. Recall Le Chatelier's Principle: When the concentration of a reactant increases, the equilibrium shifts to consume that reactant.

3. Apply this principle to the equation: More CO2 will drive the reaction toward the formation of H2CO3 and subsequently toward H+ and HCO3-.

4. Consider the physiological effect: Increased H+ production can lower blood pH, leading to acidosis.

Try solving on your own before revealing the answer!

Final Answer: Shifts to the right

When plasma CO2 concentration rises, the equilibrium shifts to the right, producing more H2CO3, H+, and HCO3-. This increases acidity and can contribute to respiratory acidosis.