Myelin is especially rich in what type of molecule?
A. Amino acids B. Carbohydrates C. Lipids D. Monosaccharides E. Proteins
The correct answer and explanation is:
The correct answer is C. Lipids.
Myelin is a fatty substance that forms a sheath around the axons of neurons in the central and peripheral nervous systems. It is primarily composed of lipids, making up about 70-80% of its structure. The remaining 20-30% consists of proteins. The lipid-rich composition of myelin plays a critical role in its function, which is to insulate axons and enhance the speed of electrical signal transmission along nerve fibers.
The primary lipid in myelin is phospholipids, including sphingomyelin and galactocerebrosides. These lipids help form the bilayer structure of myelin. The lipid bilayer acts as an electrical insulator, preventing the loss of the electrical signal as it travels down the axon. This allows nerve impulses to travel faster through the axons, improving the efficiency of the nervous system.
The myelin sheath is formed by specialized cells, oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. The wrapping of these cells around the axon creates a segmented sheath, with small gaps between the segments known as Nodes of Ranvier. These gaps allow for the rapid conduction of nerve impulses through a process called saltatory conduction, where the electrical signals jump from node to node, significantly speeding up the transmission.
While proteins are also present in myelin, they mainly serve structural and functional roles, such as stabilizing the lipid bilayer or interacting with ion channels to facilitate signal transmission. Amino acids, carbohydrates, and monosaccharides are not the primary components of myelin, although they may be involved in other cellular processes.