This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cell Membrane and transpo protiens, Subject name: Physiology
The cell membrane consists of various components, including integral proteins. These integral proteins 
Select and explain. 
A. Are not attached to the outer leaflet, B. Are not attached to the inner leaflet, C. Include transmembrane proteins, D. Are preferentially attached to the surface
C: Include transmembrane proteins
Answer: C: Include transmembrane proteins 
Explanation: The membrane proteins are classified into two categories: Integral proteins or intrinsic membrane proteins Peripheral proteins or extrinsic membrane proteins. Integral proteins are not only closely associated with the lipid bilayer but also tightly bound to the cell membrane.