Question

Th pH of blood is steady at a value of approximately 7.4 as a result of the following equilibrium reactions: $$ \mathrm{CO}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \leftrightharpoons \mathrm{H}_{2} \mathrm{CO}_{3}(a q) \leftrightharpoons \mathrm{HCO}_{3}-(a q)+\mathrm{H}^{+}(a q) $$ The actual buffer system in blood is made up of \(\mathrm{H}_{2} \mathrm{CO}_{3}\) and \(\mathrm{HCO}_{3}\) - One way the body keeps the pH of blood at 7.4 is by regulating breathing. Under what blood ph conditions will the body increase breathing and under what blood pH conditions will the body decrease breathing? Explain.

Short answer

In conclusion, the body increases breathing under low blood pH (acidic) conditions to decrease the concentration of hydrogen ions (H+) and restore the pH balance. On the other hand, the body decreases breathing under high blood pH (alkaline) conditions to increase the concentration of hydrogen ions (H+) and restore the pH balance. Breathing plays a vital role in regulating the blood pH by controlling the concentrations of CO2 and H2CO3 in the blood, through the blood buffering system.

Step-by-step solution

Understanding the blood buffering system

Blood buffering system consists of carbon dioxide (CO2) dissolved in water (H2O), carbonic acid (H2CO3), bicarbonate ion (HCO3-), and a hydrogen ion (H+). These substances are in equilibrium with each other, as shown in the provided reactions: $$ \mathrm{CO}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \leftrightharpoons \mathrm{H}_{2} \mathrm{CO}_{3}(a q) \leftrightharpoons \mathrm{HCO}_{3}-(a q)+\mathrm{H}^{+}(a q) $$ The pH of the blood is mainly determined by the concentration of hydrogen ions (H+) in the blood. The more hydrogen ions present, the lower the pH value will be, and the more acidic the blood becomes.

Identify the role of Breathing in the Blood Buffering System

Breathing plays a crucial role in maintaining the appropriate pH in the blood. When we breathe in, we take in oxygen (O2) and expel carbon dioxide (CO2). The process of inhaling and exhaling air helps in regulating the concentrations of CO2 and H2CO3 in the blood, thereby controlling the blood pH.

Determine the conditions for increased Breathing

If the blood pH becomes too low (acidic) due to a higher concentration of hydrogen ions (H+), the body tries to restore the pH balance by eliminating more carbon dioxide (CO2) through increased breathing. Increased breathing causes the blood buffering system to shift the equilibrium to the left, according to the reactions: $$ \mathrm{CO}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \leftrightharpoons \mathrm{H}_{2} \mathrm{CO}_{3}(a q) \leftrightharpoons \mathrm{HCO}_{3}-(a q)+\mathrm{H}^{+}(a q) $$ As a result, the concentration of hydrogen ions (H+) decreases, and the pH of the blood increases.

Determine the conditions for decreased Breathing

If the blood pH becomes too high (alkaline) due to a lower concentration of hydrogen ions (H+), the body tries to restore the pH balance by retaining more carbon dioxide (CO2) through decreased breathing. Decreased breathing causes the blood buffering system to shift the equilibrium to the right, according to the reactions: $$ \mathrm{CO}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \leftrightharpoons \mathrm{H}_{2} \mathrm{CO}_{3}(a q) \leftrightharpoons \mathrm{HCO}_{3}-(a q)+\mathrm{H}^{+}(a q) $$ As a result, the concentration of hydrogen ions (H+) increases, and the pH of the blood decreases.

Conclusion

In conclusion, the body increases breathing under low blood pH (acidic) conditions to decrease the concentration of hydrogen ions (H+) and restore the pH balance. On the other hand, the body decreases breathing under high blood pH (alkaline) conditions to increase the concentration of hydrogen ions (H+) and restore the pH balance. Breathing plays a vital role in regulating the blood pH by controlling the concentrations of CO2 and H2CO3 in the blood, through the blood buffering system.

Key concepts

pH regulation

The regulation of pH in the body, particularly in the blood, is an essential physiological process. The pH scale measures how acidic or alkaline a solution is, with 7 being neutral. The blood's pH is tightly controlled between 7.35 and 7.45 to ensure optimal functioning of biological processes. This slight alkalinity is crucial for metabolic functions and enzyme activities.
One of the main ways the body maintains this balance is through the carbonic acid-bicarbonate buffering system. This system involves multiple components that can accept or donate hydrogen ions ( ext{H}^+ ext{ ions}) to prevent significant shifts in pH levels.
The concentration of hydrogen ions in the blood directly influences the pH value.

• Higher concentration of ext{H}^+ ext{ ions} means lower pH (more acidic).
• Lower concentration of ext{H}^+ ext{ ions} means higher pH (more alkaline).

Breathing patterns are influenced by blood pH levels. When blood pH dips below its normal range (acidosis), the body responds by increasing respiration, thus expelling ext{CO}_2 and increasing pH. Conversely, if blood pH rises above normal (alkalosis), breathing slows down, retaining ext{CO}_2 which lowers pH back to normal levels.

carbon dioxide equilibrium

Carbon dioxide plays a crucial role in maintaining the body's pH balance. It participates in equilibrium reactions that manage acidity levels in the blood. The key reactions include the conversion of carbon dioxide and water into carbonic acid ( ext{H}_2 ext{CO}_3), which then dissociates into bicarbonate ( ext{HCO}_3^- ext{ }) and hydrogen ions ( ext{H}^+ ext{ }).
The equilibrium can be described as:\[\mathrm{CO}_2(aq) + \mathrm{H}_2\mathrm{O}(l) \leftrightharpoons \mathrm{H}_2\mathrm{CO}_3(aq) \leftrightharpoons \mathrm{HCO}_3^- (aq) + \mathrm{H}^+ (aq)\]This dynamic balance ensures that blood pH remains stable under varying physiological conditions.

• During increased metabolic activity, like exercise, more ext{CO}_2 is produced, pushing the equilibrium to the right, thus decreasing pH (more acidic).
• During rest, less ext{CO}_2 is produced, allowing pH to increase (more alkaline).

Proper breathing regulates these equilibrium shifts by controlling ext{CO}_2 levels. Faster breathing removes more ext{CO}_2, shifting equilibrium left, thus reducing acidity. Slower breathing retains ext{CO}_2, shifting equilibrium right, thus increasing acidity.

bicarbonate ion

Bicarbonate ions ( ext{HCO}_3^-) are vital components of the blood buffering system, working alongside carbonic acid to maintain pH levels within a narrow range. They act as a buffer by neutralizing excess acids or bases, thereby stabilizing the blood's pH.
ext{HCO}_3^- ions have a pivotal role in the buffering equation:\[\mathrm{H}_2\mathrm{CO}_3 \leftrightharpoons \mathrm{HCO}_3^- + \mathrm{H}^+\]In this role, bicarbonate acts as a reservoir for the hydrogen ions, helping to soak up excess ext{H}^+ ext{ ions} when the blood becomes too acidic, and releasing ext{H}^+ ext{ ions} when it becomes too alkaline.

• An increase in ext{HCO}_3^- in the blood indicates an alkaline environment, which facilitates the binding of ext{H}^+ ext{ ions} to lower pH if necessary.
• A decrease suggests a shift to acidity, requiring the release of ext{H}^+ ext{ ions} to raise pH.

This ion's concentration is also closely tied to kidney function, which can adjust the levels of ext{HCO}_3^- by filtering them from the blood, ensuring that the pH remains stable over longer periods beyond immediate respiratory adjustments.