`CO_(2)` dissolving in water in living systems

Options

A. is an uncatalysed reaction
B. is a catalysed reaction
C. may be catalysed or uncatalysed
D. Does not occur

Answer

To understand the process of CO₂ dissolving in water within living systems, we can break it down into the following steps:

### Step 1: Understanding the Reaction
When carbon dioxide (CO₂) dissolves in water (H₂O), it undergoes a chemical reaction to form carbonic acid (H₂CO₃). This reaction can be represented as:
\[ \text{CO}_2 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{CO}_3 \]

### Step 2: Identifying the Role of Enzymes
In living systems, this reaction is significantly influenced by enzymes. Specifically, the enzyme involved in this process is called carbonic anhydrase. Enzymes are biological catalysts that speed up chemical reactions.

### Step 3: Comparing Catalyzed vs. Uncatalyzed Reactions
- **Uncatalyzed Reaction**: In the absence of carbonic anhydrase, the formation of carbonic acid from CO₂ and H₂O occurs very slowly. It is estimated that only about 200 molecules of H₂CO₃ are produced in one hour without the enzyme.
- **Catalyzed Reaction**: With the presence of carbonic anhydrase, the reaction rate increases dramatically. The enzyme facilitates the conversion of CO₂ and H₂O to H₂CO₃ at a rate of approximately 600,000 molecules per second.

### Step 4: Conclusion
Given the significant increase in the reaction rate due to the presence of the enzyme, we conclude that the process of CO₂ dissolving in water in living systems is a catalyzed reaction. Therefore, the correct answer is option B.

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