Every living cell in the human body must have an energy supply. Cells take up glucose or a related chemical and break it down inside the mitochondria to produce ATP. ATP is the form of energy that cells use for their various activities. The breakdown of glucose occurs in the process of cellular respiration. A summary of this process is shown in the following equation (note that this is not a balanced equation):
C6H12O6 + O2 « CO2 + H2O + ATP
O2, which is a gas, is consumed in this process, and CO2, also a gas, is produced. Trace the pathway of a molecule of O2 from where it enters the human body, across any cell membranes it must pass, until it reaches a muscle cell in the right leg. Then, trace the pathway of a molecule of CO2 from inside that muscle cell, where it is produced in cellular respiration, until it leaves the body.