Oxygen in
Oxygen is a gas used inside the mitochondrion to accept electrons during mitochondrial energy production.
Breathe
Oxygen accepts electrons inside mitochondria, carbon dioxide is produced by energy reactions, and gas transporters move gases across membranes.
CO2 out
Carbon dioxide is a gas and a waste product of reactions which produce energy.
Gas transport
Gas uniporters move gas across membranes, while hemoglobin is the oxygen carrying protein contained in red blood cells.