Larger molecules wold require a transport protein in order to cross the cell membrane.
There are three modes of transport across the cell membrane: diffusion, facilitated diffusion, and active transport.
Diffusion is the movement of substances down a concentration gradient (from higher to lower concentration). There is no transport protein involved. Smaller ions and molecules are transported across the membrane in this way.
Facilitated diffusion also transports substances down a concentration gradient. However, it requires a transmembrane integral protein, which helps transport larger molecules. The proteins are specific to allow certain things in and keep harmful substances out (hence, we call the membrane "selective").
Becuase diffusion and facilitated diffusion do not require energy, they are referred to as modes of passive transport.
The last form of transportation is active transport. It carries substances against the concentration gradient (from low to high concentrations). It, too, requires a transport protein.
Thus, because the larger protein would require a transport protein, it would travel via either facilitated diffusion or active transport.