Which of the following is incorrect about the transport of gases by blood?

Options

A. The oxygen dissociation curve is sigmoid and shifts to the right at high `PCO_2` , and low pH.
B. Every 100 ml of oxygenated blood can deliver around 5 ml of `O_2` to the tissues under normal physiological conditions .
C. The major factor affecting the formation of carbamino - hemoglobin is low `H^+` concentration.
D. Approximately 70% of carbon dioxide is carried as bicarbonates

Answer

To solve the question regarding the incorrect statement about the transport of gases by blood, we will analyze each of the provided statements step by step.

### Step-by-Step Solution:

1. **Understanding Oxygen Transport**:
- Approximately 97% of oxygen is transported by red blood cells (RBCs) bound to hemoglobin.
- The remaining 3% of oxygen is dissolved in plasma.
- This statement is **correct**.

2. **Understanding Carbon Dioxide Transport**:
- About 70% of carbon dioxide is transported in the form of bicarbonate ions (HCO3-) in the plasma.
- The remaining carbon dioxide is transported as carbaminohemoglobin (bound to hemoglobin) and dissolved in plasma.
- This statement is **correct**.

3. **Examining the Role of Hemoglobin**:
- Hemoglobin binds oxygen in a reversible manner to form oxyhemoglobin.
- The oxygen-hemoglobin dissociation curve is sigmoid in shape.
- Factors such as pH, temperature, and partial pressure of carbon dioxide affect this curve.
- This statement is **correct**.

4. **Analyzing the Incorrect Statement**:
- The statement claims that the major factor affecting the formation of carbaminohemoglobin is low hydrogen ion concentration.
- However, the major factor affecting the binding of carbon dioxide to hemoglobin (as carbaminohemoglobin) is the partial pressure of carbon dioxide, not hydrogen ion concentration.
- Therefore, this statement is **incorrect**.

### Conclusion:
The incorrect statement about the transport of gases by blood is the one that claims the major factor affecting the formation of carbaminohemoglobin is low hydrogen ion concentration.

### Final Answer:
The incorrect statement is the third option: "The major factor affecting the formation of carbaminohemoglobin is low hydrogen ion concentration."

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