Question

Try to hold your breath as long as you can. You might have observed great discomfort in the body. This is due to increase in ${CO}_2$ levels in the lungs and the respiratory part of the brain forces you to breathe and sends painful contractions of the diaphragm and muscles in the ribs. Where does this ${CO}_2$ come from in the first place?

• A. Burning of glucose in muscles.
• B. End product of cellular respiration.
• C. Burning of glucose when we work out.
• D. None of these.

Answer 1

The correct option is B End product of cellular respiration.

The glucose obtained by every cell is carbon compound but not a form of energy that can be directly utilized by the body. So it is broken down into pyruvate which is a 3 carbon compound to release energy.
$C_6{H}_{12}{O}_6\to 2Pyruvate+2ATP+2NADH$
The ATP and NADH are energy molecules which can be used by the cells.

Pyruvate further undergoes a cycle of changes to release more energy and carbon dioxide. The energy obtained in this process is utilized by the cells.
$Pyruvate\to 6C{O}_2+Energy$
The $C{O}_2$ obtained is diffused into the blood at the cell membrane due to the concentration difference of $C{O}_2$ in the cells and blood. The carbon dioxide in the blood then diffuses into the lungs and waits for the next exhalation to release into the air.