Question

Proteins that penetrate the lipid bilayer _________.

1) are called integrated proteins.
2) may pass entirely through the lipid bilayer and protrude from both the extracellular and cytoplasmic sides of the membrane.
3) are called lipid-anchored proteins.
4) All of these statements are correct.

Answer 1

Proteins that penetrate the lipid bilayer are called integral or transmembrane proteins. They are embedded within the cell membrane and may span across the membrane, interacting with both the extracellular and cytoplasmic sides.

Step-by-step explanation:

Proteins that penetrate the lipid bilayer are embedded within the cell membrane structure and interact with the hydrophobic region of the phospholipid bilayer. These integral proteins may span the entirety of the membrane and protrude from both sides, allowing for the transportation of molecules across the cell membrane. Some of these membrane-spanning proteins, often termed transmembrane proteins, can pass completely through the lipid bilayer and extend out from both the extracellular and cytoplasmic sides of the membrane, functioning as channels or pumps.

Lipid-anchored proteins are a different class of proteins associated with the membrane, and they are not the proteins that penetrate the lipid bilayer. Rather, they are attached to the membrane lipids. Considering this clarification, the correct statements are that proteins penetrating the lipid bilayer are called integral proteins and may pass through both sides of the membrane but are not referred to as lipid-anchored proteins.