Which type of cellular transport requires energy?

• A. Passive transport
• B. Facilitated diffusion
• C. Osmosis
• D. Active transport

Answer: (D)

Active transport is the type of cellular transport that requires energy. This process involves the movement of molecules across a cell membrane against their concentration gradient, meaning that substances move from an area of lower concentration to an area of higher concentration. This is in direct contrast to passive transport, facilitated diffusion, and osmosis, all of which do not require cellular energy (typically in the form of ATP) as they rely on the natural tendency of molecules to move towards areas of lower concentration.

In active transport, specific carrier proteins or pumps are utilized to move the substances. The most well-known example is the sodium-potassium pump, which exchanges sodium ions out of the cell and potassium ions into the cell, both against their concentration gradients. This process is vital for maintaining cellular homeostasis and is essential in functions such as nutrient uptake and nerve impulse transmission.