Biology Regents Practice Exam

What is the primary function of both diffusion and active transport?

1. Break down molecules to release energy.

2. Move molecules into or out of cells of the body.

3. Bring molecules into cells when they are more concentrated outside of the cell.

4. Move molecules against a concentration gradient, using ATP molecules.

The correct answer is: Move molecules into or out of cells of the body.

The primary function of both diffusion and active transport is to move molecules into or out of cells of the body. Diffusion is a passive process where molecules move from an area of higher concentration to an area of lower concentration until equilibrium is reached. This process allows essential substances, such as oxygen and nutrients, to enter cells and waste products to exit. Active transport, on the other hand, involves the movement of molecules against their concentration gradient, which requires energy in the form of ATP. This is crucial for maintaining concentrations of ions and other substances that are necessary for cellular function. For example, the sodium-potassium pump actively transports sodium ions out of the cell and potassium ions into the cell, which is vital for processes like nerve impulse transmission. Thus, both diffusion and active transport serve as mechanisms to regulate the internal environment of cells by controlling the movement of substances across the cell membrane, ensuring that cells receive what they need while disposing of waste effectively.