Important Notice: Our web hosting provider recently started charging us for additional visits, which was unexpected. In response, we're seeking donations. Depending on the situation, we may explore different monetization options for our Community and Expert Contributors. It's crucial to provide more returns for their expertise and offer more Expert Validated Answers or AI Validated Answers. Learn more about our hosting issue here.
“Active” in this context means that energy is required. A substance will flow in a certain direction, through diffusion, without having to provide additional energy. To force the substance in the opposite direction would require energy; the cell has to be “active” to achieve this, and this requires energy.
