Protein transport refers to the process by which proteins are moved within and outside of cells. Proteins are synthesized in the ribosomes and then often need to be transported to specific locations to perform their functions. This transport can occur through various pathways, including the endoplasmic reticulum and Golgi apparatus, which help modify and package proteins for delivery. There are two main types of protein transport: passive and active. Passive transport allows proteins to move along concentration gradients without energy, while active transport requires energy to move proteins against their gradients. Both methods are essential for maintaining cellular function and communication.