Which One of the Following is Considered an Integral Membrane

Question

Which one of the following is considered an integral membrane protein?
A)a protein with its N-terminus in the cytoplasm and its C-terminus in the extracellular space
B)a protein attached to a transmembrane protein via hydrogen bonding
C)a protein attached to a phospholipid via ionic bonding with the head group of the lipid molecule
D)a protein capable of diffusing throughout the cytoplasm of a cell

Accepted Answer

An integral membrane protein is a protein that is permanently attached to the cell membrane, with portions of the protein embedded within the hydrophobic interior of the membrane. This means that the protein must span the entire membrane, with one end facing the cytoplasm and the other end facing the extracellular space. Choice A describes an integral membrane protein, while the other choices do not.