Consider the following statements regarding carbon dioxide transport.
About `7%` of `CO_2` is transported as dissolved in plasma, `23%` as carbaminohemoglobin and `70%` as bicarbonates.
The `CO_2` dissolves in plasma forms carbonic anhydrase.
The concentration of carbonic acid remains constant due to potassium.
Choose the correct option.

Options

A. Only II
B. Only III
C. Only I
D. All of these

Answer

To analyze the statements regarding carbon dioxide (CO2) transport, let's break down the information step by step:

### Step 1: Understanding CO2 Transport Mechanisms
- **Dissolved in Plasma**: About 5-7% of CO2 is transported dissolved in the plasma. This is a physical solution where CO2 is in a dissolved state.
- **Carbaminohemoglobin**: Approximately 23% of CO2 binds to hemoglobin to form carbaminohemoglobin. This occurs when CO2 reacts with the amino groups of hemoglobin.
- **Bicarbonate Formation**: The majority, around 70%, of CO2 is transported in the form of bicarbonate (HCO3-). This occurs when CO2 reacts with water (H2O) to form carbonic acid (H2CO3), which then dissociates into bicarbonate and hydrogen ions.

### Step 2: Analyzing the Statements
1. **First Statement**: "About 7% of CO2 is transported as dissolved in plasma."
- This statement is **correct** as it aligns with the known facts about CO2 transport.

2. **Second Statement**: "The CO2 dissolved in plasma forms carbonic anhydrase."
- This statement is **incorrect**. CO2 dissolved in plasma does not form carbonic anhydrase; instead, it forms carbonic acid (H2CO3) when it reacts with water. Carbonic anhydrase is an enzyme that catalyzes the conversion of CO2 and water into carbonic acid.

3. **Third Statement**: "The concentration of carbonic acid remains constant due to potassium."
- This statement is **incorrect**. The concentration of carbonic acid does not remain constant due to potassium. The concentration is primarily regulated by the equilibrium between CO2, carbonic acid, bicarbonate, and hydrogen ions in the blood, not specifically by potassium levels.

### Conclusion
Based on the analysis:
- The **first statement** is correct.
- The **second and third statements** are incorrect.

### Final Answer
The correct option regarding the statements about carbon dioxide transport is that only the first statement is correct.

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