What is the driving force behind chemical transport?

• A. Membrane potential
• B. Osmotic pressure
• C. Concentration gradient
• D. Cell volume

Answer: (C)

The correct choice is the concentration gradient, as it plays a fundamental role in chemical transport processes across cell membranes. A concentration gradient refers to the difference in the concentration of a substance between two areas. Movement occurs naturally from areas of higher concentration to areas of lower concentration, driven by the principle of diffusion. This process is essential for various biological functions, including the uptake of nutrients and the removal of waste products.

When considering the context of transport mechanisms, the concentration gradient is crucial because it determines the direction and rate of substance movement. In passive transport, such as diffusion and facilitated diffusion, molecules move down their concentration gradient without the input of energy. In contrast, active transport mechanisms utilize energy to move substances against their concentration gradient.

Membrane potential refers to the difference in electric charge across a cell membrane, which influences ion movement but is not the primary driver of chemical transport for substances that are not charged. Osmotic pressure is related to water movement across semipermeable membranes and is more specific to the distribution of water rather than the chemical transport of solutes in general. Cell volume is affected by various transport processes, but it is not the motivating factor behind the chemical movement of substances across the membrane.