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 nerve cells, providing insulation and increasing the speed at which electrical impulses (action potentials) are transmitted along the nerve fibers. This sheath is primarily composed of lipids, making it essential for the proper functioning of the nervous system.
The myelin sheath is made up of layers of lipid-rich membranes, which include phospholipids, cholesterol, and glycolipids. These lipids form a dense, insulating layer that prevents the leakage of electrical signals, ensuring that the impulses are conducted rapidly and efficiently. The lipid composition of myelin contributes to its high resistance to electrical current, allowing for faster transmission of nerve signals. This is particularly important in the central nervous system (CNS), where myelin enables the rapid coordination of brain and spinal cord functions.
Additionally, myelin is not just a passive insulator but actively facilitates signal conduction. The gaps in myelin, called nodes of Ranvier, allow action potentials to “jump” from one node to the next in a process known as saltatory conduction. This leapfrogging of the action potential from node to node dramatically increases the speed of nerve signal transmission.
While myelin contains some proteins that are important for maintaining its structure and function, lipids are by far the dominant molecules. For example, oligodendrocytes in the CNS and Schwann cells in the peripheral nervous system are responsible for synthesizing myelin, and they do so by producing large quantities of lipids. Without the lipid-rich myelin sheath, nerve impulses would travel much more slowly, and the nervous system’s overall efficiency would be compromised.