Answer:
Phospholipids relate to the selective permeable membrane of the cells, acting to prevent certain molecules from crossing the membrane freely through its structure and it's ability to accommodate various protein molecules in and through the lipid layer forming channels and transport mechanisms in the cell membrane.
Phospholipids are lipids that contain a phosphate group consisting of a hydrophobic (water-loving) head and an hydrophobic (water-hating) tail.
Phospholipids are crucial in building the protective barrier around the cells of the body.
Essentially, phospholipids are triglycerides which a fatty acid has been removed or replaced by a phosphate group.
How does this structure helps in selective permeability of the cell membrane?
The external environment which is aqueous of the cell allows the huddling together of the hydrophobic parts of the membrane in the center of the membrane, leaving the Polar parts exposed to water on both surfaces. This result in the formation of a double layer of phospholipids in the cell membrane.
The hydrophobic middle of the membrane restricts the passage of water and water-soluble molecules and ions. Certain polar compounds do pass through the membrane however.
Also, this selective activity of the membrane is accomplished by the embedded protein molecules in and through the lipid bilayer.
These proteins form channels and transport route through which certain specific molecules and ions are transported through the membrane.
These proteins include, peripheral proteins which are only partially embedded in one part of the membrane; integral proteins span through the membrane from one part to the other.
However, because the membrane is not solid, the proteins within the phospholipid can move freely laterally. Due to their unequal distribution and constant changing mosaic pattern which is called the Fluild-Mosaic Model of Membrane Structure.
Many membrane proteins also contain attached carbohydrates on the outside of the lipid bilayer allowijv it to form hydrogen bond with water.
All these characteristics allow it to aid the selective permeable role of the cell membrane
