Problem 13 - Biology of Humans: Concepts, Applications, and Issues

Question

The enzyme in red blood cells that reversibly converts carbonic acid to bicarbonate ions and hydrogen ions is ______.

Step-by-Step Solution

Answer

The enzyme is carbonic anhydrase.

Step 1: Identify the role of the enzyme

Determine which enzyme in red blood cells is responsible for converting carbonic acid to bicarbonate ions and hydrogen ions. This process involves balancing pH levels in the blood.

Step 2: Recognize the enzyme

The specific enzyme that facilitates this reversible conversion is 'carbonic anhydrase'. It catalyzes the reaction, helping to maintain acid-base balance in the blood.

Key Concepts

enzyme function

Enzymes are proteins that speed up chemical reactions in the body. They are biological catalysts. This means they reduce the energy needed for reactions to occur.
Enzymes play a crucial role in many bodily functions, from digestion to DNA replication.

• Each enzyme acts on a specific substance, called a substrate.
• The enzyme binds to the substrate at its active site, forming an enzyme-substrate complex.
• After the reaction, the enzyme releases the products and remains unchanged, ready to catalyze another reaction.

The enzyme discussed here is carbonic anhydrase. It catalyzes the conversion of carbonic acid to bicarbonate ions and hydrogen ions inside red blood cells.

red blood cells

Red blood cells (RBCs) are vital components of our blood. They carry oxygen from the lungs to the rest of the body and return carbon dioxide back to the lungs for exhalation.
RBCs contain hemoglobin, a protein that binds to oxygen, making it possible for oxygen to be transported in the blood. Besides transporting gases, RBCs also help maintain acid-base balance thanks to the presence of enzymes like carbonic anhydrase.

• Each red blood cell is flexible and biconcave in shape, allowing it to navigate through narrow blood vessels.
• RBCs have a lifespan of about 120 days, after which they are broken down in the spleen and liver.

acid-base balance

Maintaining the acid-base balance in the body is crucial for normal cellular functions. The balance ensures that blood pH stays within a narrow, slightly alkaline range (around 7.4). Carbonic anhydrase plays an important role here.
This enzyme helps regulate pH by converting carbonic acid into bicarbonate and hydrogen ions.
This conversion helps buffer pH changes in the blood.

• If the blood becomes too acidic (low pH), carbonic anhydrase works to restore balance by increasing bicarbonate levels to neutralize excess hydrogen ions.
• If the blood becomes too alkaline (high pH), the enzyme aids in converting bicarbonate back into carbonic acid.

Thus, carbonic anhydrase helps the body swiftly respond to changes, keeping the pH level stable.

bicarbonate ions

Bicarbonate ions (HCO₃⁻) are critical in maintaining the pH balance in the blood. They act as a buffer, neutralizing excess acids and bases. When carbon dioxide dissolves in water within red blood cells, it forms carbonic acid, which then dissociates into bicarbonate ions and hydrogen ions through the action of carbonic anhydrase.

• Bicarbonate ions can quickly neutralize excess hydrogen ions, preventing the blood from becoming too acidic.
• They are transported in the plasma to the lungs, where they are converted back to carbon dioxide for exhalation.

This conversion is reversible and helps control the blood pH optimally. In essence, bicarbonate ions are a part of the body’s buffer system, acting instantly to maintain a healthy pH level.