An oxygen molecule is inhaled into the lungs and transported to a cell in the liver. The passage below describes its journey. Complete the sentences in the passage by writing a suitable word or words on each dotted line.
The oxygen molecule diffuses from the air sacs in the lungs, called .................................................... , into the surrounding blood. It travels to the left atrium of the heart via the pulmonary .................................................... .
From the left atrium, the oxygenated blood passes into the left .................................................... . It is then pumped out of the heart through the largest artery in the body, called the .................................................... .
This artery branches, and some blood enters the liver via the hepatic .................................................... . Within the liver, the oxygen leaves the blood through the thin walls of the smallest blood vessels, called .................................................... , to reach the liver cells.
Inside the liver cells, the oxygen is used in a metabolic process called .................................................... to release energy.
