The chemical composition of lens-fiber plasma membranes suggests that they are both very stable and very rigid. A high saturated fatty acid content, a high cholesterol-to-phospholipid ratio, and a high concentration of sphingomyelin all contribute to the tight packing and low fluidity of the membrane. Although lipids make up only about 1% of the total lens mass, they constitute approximately 55% of the plasma membrane’s dry weight; cholesterol is the major neutral lipid. As the lens ages, the protein-to-lipid and cholesterol-to-phospholipid ratios increase as a result of phospholipid loss, especially in the nucleus.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.