Transport proteins are specialized proteins that help move substances across cell membranes. They play a crucial role in maintaining the balance of ions, nutrients, and waste products within cells. These proteins can facilitate the movement of molecules either passively, without energy, or actively, using energy from ATP to transport substances against their concentration gradient. There are two main types of transport proteins: channel proteins and carrier proteins. Channel proteins form openings in the membrane that allow specific molecules to pass through, while carrier proteins bind to substances and change shape to shuttle them across the membrane. Together, they ensure that essential materials enter and exit cells efficiently.