What are the characteristics of membrane lipids?

Every lipid molecule present in cell membranes exhibits amphipathic characteristics, meaning it has both a hydrophilic polar end and a hydrophobic nonpolar end. The predominant type of membrane lipids are phospholipids, which consist of a polar head group and two hydrophobic hydrocarbon tails. The tails are typically composed of fatty acids and vary in length, usually containing between 14 and 24 carbon atoms. One of the tails typically features one or more cis-double bonds, making it unsaturated, while the other tail lacks such double bonds and is saturated. Membrane lipids contribute to the fluidity of the cell membrane. The degree of unsaturation in fatty acid tails influences membrane fluidity, with more unsaturated lipids contributing to increased fluidity. Additionally, membrane lipids have a crucial role in the selective permeability of cell membranes. The lipid bilayer restricts the passage of certain molecules, allowing the cell to control the entry and exit of substances.