A) Incorporation of phospholipids with longer fatty acid chains.
B) Introduction of double bonds in the fatty acids.
C) Addition of cholesterol.
D) Removal of serine from the head group.
E) None of the above.

A) are typically exposed only to one side of the membrane.
B) can be released from the membrane by a gentle extraction procedure such as salt treatment.
C) are often further attached to the membrane via a GPI anchor.
D) are sometimes covalently attached to a fatty acid chain that inserts into the membrane.
E) cannot contain β sheets in the part of their structure that interacts with the membrane interior.

A) may contain oligosaccharide chains with negatively charged residues.
B) are found to constitute about 10% of the total lipid mass in the plasma membrane of neurons.
C) are found in the extracellular leaflet (facing away from the cytosol) in the cellular membranes.
D) affect the electrical environment of the membrane.
E) All of the above