Phospholipids: divided into glycerophospholipids and sphingomyelin, accounting for more than 50%

Glycolipid: less than 5%; 5%-10%

Sterol: Cholesterol and its analogs are collectively called sterols or sterols, ≤1/3

Lateral diffusion: adjacent lipid molecules on the same plane exchange positions

Rotational motion: membrane lipid molecules rotate rapidly around an axis perpendicular to the plane of the membrane

Oscillating motion: Membrane lipid molecules swing left and right around an axis perpendicular to the plane of the membrane.

Turning motion: Membrane lipid molecules flip from one layer of the lipid bilayer to another. It is completed under the catalysis of flippase

Support, membrane lipids are the skeleton of the cell membrane structure

Maintain conformation and provide an environment for membrane proteins to function

Necessary for some enzymes to function

Intrinsic (integrated) membrane proteins: water-insoluble proteins that form transmembrane helices and are tightly bound to the membrane. Detergents are required to disintegrate the membrane before they can be separated.

Extrinsic (peripheral) membrane proteins: water-soluble proteins that are non-covalently bound to the polar heads of protein molecules or lipid molecules on the membrane surface by ionic bonds or other weak bonds, and are easy to separate.

Lipid-anchored membrane protein: anchored to the plasma membrane by inserting the attached lipid molecule into the lipid bimolecule of the membrane

Ionic detergent (SDS)

Non-ionic detergent (Triton X-100)

Produced by: lateral movement of membrane lipid molecules

Influencing factors

Produced by: spontaneous heat movement

experimental evidence

Influencing factors

extracellular surface ES

plasma membrane protoplasmic surface PS

Extracellular pagelet fracture surface EF

Protoplasm small page fracture surface PF

Glycolipids only exist on the ES surface of the plasma membrane and are the structural basis for completing their physiological functions.

The asymmetry of membrane proteins means that each membrane protein molecule has a clear directionality on the cell membrane.

The sugar residues of glycoproteins are uniformly distributed on the ES surface of the plasma membrane.

The asymmetry of membrane proteins is the guarantee for biological membranes to complete various physiological functions that are complex and ordered in time and space.