Transport proteins are specialized molecules found in cell membranes that help move substances in and out of cells. They play a crucial role in maintaining the balance of nutrients, ions, and waste products. By facilitating the movement of these substances, transport proteins ensure that cells function properly and can respond to their environment. There are two main types of transport proteins: channel proteins and carrier proteins. Channel proteins create openings that allow specific molecules, like ions, to pass through the membrane easily. In contrast, carrier proteins bind to a substance and change shape to shuttle it across the membrane, making them essential for transporting larger or polar molecules.