What kind of proteins move solutes against the concentration gradient?

Transporter proteins are essential for moving solutes against their concentration gradient, a process known as active transport. Unlike channel proteins, which facilitate passive transport by allowing molecules to flow down their concentration gradient, transporter proteins utilize energy, often in the form of ATP, to move substances from areas of lower concentration to areas of higher concentration. This mechanism is crucial for maintaining concentration gradients across membranes, which are vital for various cellular functions, such as nutrient uptake, ion balance, and waste removal.

Structural proteins provide support and shape to cells and tissues, while receptor proteins are involved in cell signaling and communication, responding to external signals but not directly involved in transport processes. Hence, the role of transporter proteins is specifically geared towards the active movement of solutes across membranes, making them the correct choice for the question.