Choose which of the following statements is correct.

• A. The pressure gradient for O₂ is much less than the pressure gradient for CO₂, but because of hemoglobin, more O₂ can be carried in the blood.
• B. Because the pressure gradient for O₂ is greater than the pressure gradient for CO₂, more molecules of O₂ will be exchanged in the alveoli than molecules of CO₂.
• C. Most molecules of O₂ are carried by hemoglobin, but it is the gradient between the plasma and the alveoli that determines the movement of O₂ in and out of the blood.
• D. O₂ is 20 times more soluble than CO₂, meaning that much more O₂ can be carried in the blood plasma than CO₂.

Answer: (C)

Verified step by step guidance

1. Understand the concept of pressure gradients: Pressure gradients refer to the difference in partial pressures of gases between two areas, such as the alveoli and the blood. This gradient drives the movement of gases during respiration.
2. Consider the solubility of gases: Solubility affects how gases are transported in the blood. CO2 is more soluble in blood plasma than O2, which influences how each gas is carried and exchanged.
3. Examine the role of hemoglobin: Hemoglobin is a protein in red blood cells that binds to O2, allowing more O2 to be carried in the blood than would be possible based on solubility alone.
4. Analyze the statements: Evaluate each statement based on your understanding of pressure gradients, solubility, and hemoglobin's role in gas transport.
5. Identify the correct statement: The correct statement should accurately reflect the relationship between pressure gradients, solubility, and hemoglobin's role in the transport of O2 and CO2 in the blood.