Diffusion Limits Cell Size. Diffusion: Random movement of particles form an area of higher concentration to area of lower concentration. Diffusion is a fast and efficient process over small distancesOver large distances becomes very slow and inefficient. DNA Limits Cell Size. DNA stored in the cells nucleus is the blue print for proteins needed for cell function.There is a limit to how quickly the blueprints can be copied in the nucleus to make proteins in the cytoplasm. .