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 "Which of the following is incorrect about the transport of gases by blood?", we will analyze each statement provided in the options.

### Step-by-Step Solution:

1. **Understanding the Oxygen Dissociation Curve**:
- The oxygen dissociation curve represents the relationship between the partial pressure of oxygen (pO2) and the saturation of hemoglobin with oxygen.
- It is indeed a sigmoid (S-shaped) curve, which indicates that as the pO2 increases, the saturation of hemoglobin with oxygen also increases.
- This statement is **correct**.

2. **Oxygen Delivery by Blood**:
- Under normal physiological conditions, approximately 100 ml of oxygenated blood delivers around 5 ml of oxygen to the tissues.
- This is a standard physiological fact and is **correct**.

3. **Formation of Carbaminohemoglobin**:
- The statement claims that the major factor affecting the formation of carbaminohemoglobin is low H+ ion concentration.
- This is **incorrect**. The formation of carbaminohemoglobin is primarily influenced by the partial pressure of carbon dioxide (pCO2). Higher pCO2 leads to more carbaminohemoglobin formation, not low H+ ion concentration.

4. **Carbon Dioxide Transport**:
- It is stated that approximately 70% of carbon dioxide is carried as bicarbonates in the blood.
- This is accurate; carbon dioxide reacts with water to form bicarbonate ions (HCO3-) in the presence of the enzyme carbonic anhydrase. This statement is **correct**.

### Conclusion:
Based on the analysis of the statements, the **incorrect statement** regarding the transport of gases by blood is the third statement about the formation of carbaminohemoglobin.

### Final Answer:
The incorrect statement is: **The major factor affecting the formation of carbaminohemoglobin is low H+ ion concentration.**

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