Final answer:
Hydrophobic interactions drive hydrophobic regions of globular proteins towards the interior to reduce the system's free energy, while hydrophilic regions stay on the surface; this folding is essential for protein functionality and stability.
Step-by-step explanation:
In globular proteins, the hydrophobic regions naturally go towards the interior of the protein, while the hydrophilic regions are found on the surface. This is due to hydrophobic interactions, where the exclusion of nonpolar substances by water molecules results in a decrease in the system's free energy. When protein folding takes place, the hydrophobic interactions drive hydrophobic amino acid R groups to aggregate in the center, away from water. This results in van der Waals forces between the hydrophobic R groups and helps to stabilize the protein's final three-dimensional structure.
Proteins embedded in a lipid bilayer, such as those in cell membranes, have hydrophobic regions that interact with the hydrophobic tails of phospholipids, while hydrophilic regions remain exposed to aqueous environments, maintaining the protein's functionality and orientation within the membrane.