The voltage across the cell membrane during active transport is called the membrane potential. Specifically, it is often referred to as the resting membrane potential when the cell is not actively in transport mode, or it can change during the process of active transport itself.
Active transport is a process that moves ions or molecules against their concentration gradient, which requires energy usually in the form of ATP. During this process, ion pumps (like the sodium-potassium pump) help maintain the voltage difference across the membrane. This voltage difference is crucial for various cellular functions, including nerve impulse transmission and muscle contraction.
In summary, the membrane potential reflects the electrical charge difference across the plasma membrane of the cell, and it plays a key role during active transport processes.