Final answer:
The cell membrane is described as a fluid mosaic because of the lateral movement of its component proteins and lipids, which are loosely attached and can move relative to one another.
Step-by-step explanation:
The description of the cell membrane as a fluid mosaic refers to the ability of its components, which include integral proteins and lipids, to move laterally within the plane of the membrane. This movement is due to the separate but loosely attached nature of these molecules. They are not fixed in place but can move around somewhat relative to one another, similar to tiles in a mosaic artwork.
The membrane's fluidity is crucial for its functions, allowing for flexibility, the motion of membrane components required for transport, and the activity of certain enzymes and transport molecules within the membrane. It is important to note that while the membrane is fluid, it is also fairly rigid and can burst if subjected to too much stress, such as being penetrated or if a cell takes in too much water. However, its fluidity allows it to self-seal after being penetrated by something as fine as a needle.
The fluid mosaic model describes the structure of the plasma membrane as a mosaic of components, including phospholipids, cholesterol, proteins, and carbohydrates. This model explains how the membrane behaves like a fluid, allowing its components to move laterally within the cell membrane. The lateral movement of integral proteins and lipids in the membrane gives it the description of a fluid mosaic. This fluidity is important for various cellular processes including transport and flexibility.