Answer:
Oxygen molecules are small and nonpolar, which allows them to easily pass through the cell membrane.
Answer: It can do this easily because the oxygen molecule (O2) is very small and has no charge or polarity. The oxygen is used up rapidly by mitochondria. This rapid consumption causes oxygen to constantly move into the cell from the blood. It too is small and uncharged so it can pass through cell membranes easily.
Explanation:
