Final answer:
Active transport requires energy in the form of ATP to move substances against their concentration gradient across the plasma membrane. ATP energizes protein carriers, such as pumps and vesicles, to transport ions and larger molecules necessary for cellular function.
Step-by-step explanation:
True, active transport requires energy to move substances across the plasma membrane against their concentration gradient. This process is essential for maintaining cellular function, as it allows cells to take in nutrients and expel waste against concentration gradients, which passive transport cannot do since it only moves substances along the gradient without energy input. The energy for active transport comes from ATP (adenosine triphosphate), which is utilized by protein carriers such as pumps and vesicle transportation systems found in the cell membrane.
Common examples of active transport include the sodium-potassium pump, which is vital for nerve impulse transmission and muscle contraction. Here, ATP provides the energy required for the pump to move sodium ions out and potassium ions into the cell, which is against their concentration gradients. Vesicle transport, another form of active transport, uses energy to transport larger molecules through the cell membrane.