Molecular transport refers to the movement of molecules across cell membranes or within cells. This process is essential for maintaining cellular functions, as it allows nutrients, waste products, and signaling molecules to enter and exit cells. There are two main types of molecular transport: passive transport, which does not require energy, and active transport, which requires energy to move molecules against their concentration gradient. In passive transport, molecules move from areas of high concentration to low concentration, often through protein channels or lipid bilayers. Active transport, on the other hand, involves transport proteins that use energy, usually from ATP, to move molecules in the opposite direction. Both processes are crucial for cellular homeostasis and overall organism health.