Final answer:
Nuclear pore complexes allow small molecules through by passive diffusion and require active transport for large molecules, such as RNA and proteins, which needs energy usually in the form of ATP hydrolysis.
Step-by-step explanation:
Nuclear pore complexes permit small molecules to pass through by passive diffusion; movement of large molecules (RNA, protein) requires active transport. Passive diffusion allows molecules such as oxygen and carbon dioxide to freely move through the pore with no energy requirement since this process relies on a concentration gradient.
In contrast, large molecules like RNA and proteins cannot pass freely through the nuclear pore complexes due to their size and need assistance from transport proteins. These macromolecules are actively transported through nuclear pore complexes via a mechanism that requires energy, often derived from ATP hydrolysis. This active transport is necessary to move the large molecules against a concentration gradient, requiring the input of energy.