What type of membrane protein penetrates the hydrophobic interior of the lipid bilayer?

Integral proteins are embedded within the lipid bilayer and typically span the entire membrane. Their structure often includes hydrophobic regions that interact with the fatty acid chains of the membrane, allowing them to penetrate the hydrophobic interior effectively. This characteristic enables integral proteins to perform essential functions, such as acting as channels, receptors, or enzymes within the membrane.

Peripheral proteins, in contrast, are not embedded in the lipid bilayer but associate with the membrane's surface, either on the exterior or interior side. They are often attached to integral proteins or to phospholipids and are involved in signaling and structural support but do not penetrate the lipid bilayer.

Transport proteins are a specific subset of integral proteins that facilitate the movement of molecules across the membrane. While they also penetrate the bilayer, the broader category of integral proteins encompasses all proteins that span or are embedded within the membrane.

Glycoproteins, which have carbohydrate moieties attached, can be either integral or peripheral proteins. Their primary function is typically related to cell recognition and signaling, but they are described mainly in terms of their carbohydrate components rather than their penetrative capacity within the lipid bilayer.

Thus, the correct answer is that integral proteins are the type of membrane protein that penetrate the hydrophobic interior