National League for Nursing (NLN PAX) Practice Exam

What process draws oxygen across the cell membrane from outside to inside due to a concentration gradient?

1. Osmosis

2. Active Transport

3. Diffusion

4. Cellular Respiration

The correct answer is: Diffusion

The process that draws oxygen across the cell membrane from outside to inside due to a concentration gradient is diffusion. This is a passive transport mechanism, meaning that it does not require energy. In diffusion, molecules move from an area of higher concentration to an area of lower concentration until equilibrium is reached. In the case of oxygen, it naturally moves from an area where it is in higher concentration (such as the air) to an area where it is in lower concentration (inside the cell), allowing the cell to intake the oxygen it needs for metabolic processes. Osmosis specifically refers to the movement of water through a semi-permeable membrane and is not applicable to the movement of oxygen. Active transport involves the movement of substances against their concentration gradient and requires energy in the form of ATP; hence it does not describe the movement of oxygen in this context. Cellular respiration is a metabolic process by which cells use oxygen to convert glucose into energy, but it is not a method of oxygen transport into the cell.