Question

What is the difference between the amount of O2 inspired (taken up) and the CO2 expired per minute?

• A. 20 ml/min
• B. 50 ml/min
• C. 75 ml/min
• D. 100 ml/min

Hint:

Resting O2 uptake is about 250 ml/min and CO2 output is about 200 ml/min.

Answer 1

The Correct Option is B

Step 1: Begin from the standard resting gas-exchange figures. Oxygen consumption is roughly 250 ml each minute, and carbon dioxide elimination is roughly 200 ml each minute.

Step 2: The question asks for the numerical gap between these two volumes. Subtract the smaller from the larger to get the answer.

\[250 \text{ ml/min} - 200 \text{ ml/min} = 50 \text{ ml/min}\]

Step 3: This gap exists because the respiratory exchange ratio is below one, around 0.8, on a typical mixed diet. Less CO2 is produced than O2 is consumed because fats and proteins yield less CO2 per molecule of O2 used than pure carbohydrate would.

Step 4: Hence the difference between O2 uptake and CO2 output is fifty millilitres per minute.

\[\boxed{50 \text{ ml/min}}\]