Ohio Assessment for Educators (OAE) Integrated Science (024) Practice Exam

What is active transport in cellular processes?

1. The passive movement of molecules

2. Movement of ions or molecules to lower concentration

3. Movement of ions or molecules to a higher concentration, requiring energy

4. Flow of fluids due to pressure gradients

The correct answer is: Movement of ions or molecules to a higher concentration, requiring energy

Active transport is characterized by the movement of ions or molecules against their concentration gradient, which means moving from an area of lower concentration to an area of higher concentration. This process is essential for maintaining the proper concentrations of various substances in and out of the cell, such as ions like sodium and potassium. The key aspect of active transport is that it requires energy, usually in the form of adenosine triphosphate (ATP), to facilitate this movement. This energy is needed because moving substances against their concentration gradient is not a naturally occurring process; it requires additional energy input to achieve. In contrast, passive movement, as mentioned in some other options, occurs naturally without the need for energy, moving substances down their concentration gradient. Hence, the distinction between active and passive transport is foundational to understanding cellular processes and the energy dynamics of cells.