Which process involves movement of molecules from low to high concentration and requires energy?

Which process involves movement of molecules from low to high concentration and requires energy?

• A. Diffusion
• B. Osmosis
• C. Active transport
• D. Filtration

Answer: (C)

Moving substances from a region of low concentration to a region of higher concentration requires energy and is carried out by proteins that pump molecules across the membrane. This is active transport. Cells use energy, typically from ATP, to drive these pumps, enabling them to accumulate minerals and nutrients when the gradient would otherwise oppose uptake—like ions being concentrated inside a cell or glucose being absorbed against its concentration gradient in the intestine. In contrast, diffusion and osmosis rely on the natural spread of particles from high to low concentration and do not require energy. Filtration involves pushing fluids through a membrane by pressure, rather than moving individual molecules uphill against their gradient.

Moving substances from a region of low concentration to a region of higher concentration requires energy and is carried out by proteins that pump molecules across the membrane. This is active transport. Cells use energy, typically from ATP, to drive these pumps, enabling them to accumulate minerals and nutrients when the gradient would otherwise oppose uptake—like ions being concentrated inside a cell or glucose being absorbed against its concentration gradient in the intestine.

In contrast, diffusion and osmosis rely on the natural spread of particles from high to low concentration and do not require energy. Filtration involves pushing fluids through a membrane by pressure, rather than moving individual molecules uphill against their gradient.