Eukaryotic plasma membrane has a fluid-mosaic model and consist of a double layer of either phospholipids or, in the case of chloroplasts, glycosylglycerides, in which proteins are embedded .In most membranes, proteins make up about half of the membrane’s mass. There are integral , peripheral and anchored proteins. Also plasma membrane has glycoproteins and glycolipids.The composition of the lipid components and the properties of the proteins vary in different organisms.
So, let’s look at the structure and function of phosphatidylcholine(phospholipid) and integral protein. Phosphatidylcholine is a class of phospholipids in which two fatty acids are covalently linked to glycerol, which is covalently linked to a phosphate group. Also attached to this phosphate group is a component, called the head group, such as choline .In contrast to the fatty acids, the head groups are highly polar; consequently, phospholipid molecules display both hydrophilic and hydrophobic proper ties (they are amphipathic). The nonpolar hydrocarbon chains of the fatty acids form a region that is exclusively hydrophobic—that is, that excludes water. They provide fluid and plastic properties of cell membranes.
Most integral proteins span the entire width of the phospholipid bilayer, so one part of the protein interacts with the outside of the cell, another part interacts with the hydrophobic core of the membrane, and a third part interacts with the interiot of the cell, the cytosol. They can serve as ion channels and as certain receptors that participate in signal transduction pathways.