Question

State the normal \(\mathrm{pH}\) range of blood. What gas has an effect on blood pH? (p. 256)

Short answer

Answer: The normal pH range of blood is 7.35 to 7.45, and carbon dioxide (CO2) is the primary gas that affects blood pH.

Step-by-step solution

Determine the normal pH range of blood

The normal pH range of blood is from 7.35 to 7.45, which means it is slightly alkaline. This is an essential range for the proper functioning of the body's cells and tissues.

Identify the gas that affects blood pH

Carbon dioxide (CO2) is the primary gas that has an effect on blood pH. When CO2 dissolves in blood, it forms carbonic acid (H2CO3), which can then dissociate into hydrogen ions (H+) and bicarbonate ions (HCO3-). An increase in CO2 levels in the blood leads to a decrease in pH (becoming more acidic), while a decrease in CO2 levels leads to an increase in pH (becoming more alkaline). This process helps in maintaining the acid-base balance in the blood.

Key concepts

Carbon Dioxide

Carbon dioxide (CO2) plays a crucial role in maintaining the pH balance of the blood. Our bodies produce CO2 as a byproduct of metabolism, and this gas is carried in the blood to the lungs, where it is exhaled. When CO2 dissolves in blood, it forms carbonic acid (H2CO3) through a chemical reaction with water. This carbonic acid can then dissociate into hydrogen ions (H+) and bicarbonate ions (HCO3-). This reversible reaction is essential in maintaining the pH of the blood within the normal range of 7.35 to 7.45.

An increase in carbon dioxide levels results in more carbonic acid, which in turn releases more hydrogen ions, lowering the pH and making the blood more acidic. Conversely, when CO2 levels decrease, fewer hydrogen ions are produced, raising the blood pH and making it more alkaline. This is why CO2 is a key factor in the body's acid-base balance.

Acid-Base Balance

The acid-base balance refers to the mechanism our body uses to maintain its pH within the narrow range of 7.35 to 7.45, which is slightly alkaline. This balance is vital for many physiological processes and is primarily regulated by the lungs and kidneys.

The lungs control the amount of CO2, a potential acid, through breathing. By adjusting the rate and depth of respiration, the body can either increase or decrease CO2 exhalation, thereby raising or lowering the pH of the blood. The kidneys contribute by excreting or reabsorbing bicarbonate ions (HCO3-) and hydrogen ions (H+) as needed, further fine-tuning the pH balance.

This precise regulation is crucial as fluctuations in pH, even minor ones, can significantly affect cellular function, enzyme activities, and overall metabolism. Therefore, the acid-base balance is a cornerstone of healthy physiological function.

Hydrogen Ions

Hydrogen ions (H+) are pivotal in determining the acidity or alkalinity of a solution, including our blood. The concentration of these ions is directly related to the pH level; the more hydrogen ions present, the more acidic the solution, and vice versa.

In the context of blood pH, the presence of hydrogen ions is mainly influenced by carbon dioxide levels. CO2, when dissolved in blood, reacts with water to produce carbonic acid, which can release hydrogen ions. If there is an abundance of hydrogen ions, the blood becomes more acidic (lower pH). On the other hand, if hydrogen ions are scarce, the blood becomes more alkaline (higher pH).

The body has buffer systems, such as the bicarbonate buffer system, to stabilize pH changes by binding or releasing hydrogen ions as needed. Understanding this process helps grasp how our body maintains a stable internal environment, despite different metabolic activities that might introduce excessive hydrogen ions.