EVERYDAY SCIENCE

Detailed explanation-1: -Extrinsic or peripheral membrane proteins associate loosely with the hydrophilic surfaces of the lipid bilayer or intrinsic membrane proteins. They form weak hydrophobic, electrostatic or non-covalent bonds, but do not embed with the hydrophobic core of the membrane.

Detailed explanation-2: -In addition to lipids, membranes are loaded with proteins. In fact, proteins account for roughly half the mass of most cellular membranes. Many of these proteins are embedded into the membrane and stick out on both sides; these are called transmembrane proteins.

Detailed explanation-3: -Proteins cannot passively diffuse across the cell membrane due to their size and polarity. Thus, a delivery system or technique is always required, similar to nucleic acid transfection.