Final answer:
Protein movements are limited by interactions with the extracellular fluid, other proteins, and extracellular materials. The material being transported first attaches to protein or glycoprotein receptors on the exterior surface of the plasma membrane and then passes to specific integral proteins that facilitate their passage.
Step-by-step explanation:
Protein movements are limited by interactions with the extracellular fluid, other proteins, and extracellular materials.
The material being transported first attaches to protein or glycoprotein receptors on the exterior surface of the plasma membrane and then passes to specific integral proteins that facilitate their passage.
Some of these integral proteins are collections of beta-pleated sheets that form a pore or channel through the phospholipid bilayer, while others are carrier proteins that bind with the substance and aid its diffusion through the membrane.