Which of the following statement is true `,`

Options

A. 20-25 percent `CO_(2)` is transported by RBCs.
B. 97 percent `O_(2)`is transported by RBCs
C. 70 percent `CO_(2)` is carried as bicarbonate
D. All of these are true

Answer

To determine which of the statements is true regarding the transport of gases in the human body, we can analyze each statement step by step.

### Step 1: Analyze the transport of CO2
- The first statement claims that 20 to 25 percent of CO2 is transported by red blood cells (RBCs).
- It is known that CO2 is transported in three forms: dissolved in plasma, as bicarbonate ions, and bound to hemoglobin.
- Approximately 20 to 25% of CO2 is indeed transported bound to hemoglobin in the form of carbamino compounds.

**Hint:** Remember the different forms in which CO2 is transported in the blood.

### Step 2: Analyze the transport of O2
- The second statement claims that 97 percent of O2 is transported by RBCs.
- Hemoglobin in RBCs is primarily responsible for transporting oxygen.
- It is well established that about 97% of the oxygen in the blood is carried by hemoglobin in the red blood cells.

**Hint:** Consider the role of hemoglobin in oxygen transport.

### Step 3: Analyze the transport of CO2 as bicarbonate
- The third statement claims that 70 percent of CO2 is carried as bicarbonate.
- The enzyme carbonic anhydrase catalyzes the reaction of CO2 with water to form bicarbonate ions (HCO3-), which accounts for about 70% of CO2 transport in the blood.

**Hint:** Recall the role of carbonic anhydrase in the conversion of CO2 to bicarbonate.

### Step 4: Conclusion
- Since all three statements have been verified as true:
1. 20 to 25 percent of CO2 is transported by RBCs.
2. 97 percent of O2 is transported by RBCs.
3. 70 percent of CO2 is carried as bicarbonate.

We conclude that all of these statements are true.

### Final Answer:
All of these statements are true.

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