The fluid mosaic model of membrane structure suggests that membranes Group of answer choices are composed of a single fluid layer of phospholipids and proteins are composed of a fluid bilayer of fatty acids with proteins associated on the outer and inner surfaces are composed of protein molecules embedded in a fluid bilayer of phospholipids are composed of a fluid phospholipid bilayer sandwiched between two layers of hydrophilic
The Correct Answer and Explanation is :
The correct answer is:
Membranes are composed of protein molecules embedded in a fluid bilayer of phospholipids.
Explanation:
The fluid mosaic model, proposed by S.J. Singer and Garth Nicolson in 1972, is the widely accepted model for describing the structure of cell membranes. According to this model, membranes consist of a phospholipid bilayer in which protein molecules are either embedded or attached to the surface. The bilayer is fluid, meaning the lipids and proteins can move laterally within the layer, allowing for flexibility and functionality.
Key Components:
- Phospholipid Bilayer:
The main structural component of the membrane is a double layer of phospholipids. Each phospholipid molecule consists of a hydrophilic (water-attracting) “head” and two hydrophobic (water-repelling) “tails.” The hydrophilic heads face outward towards the aqueous environments inside and outside the cell, while the hydrophobic tails face inward, away from water. This arrangement creates a semi-permeable barrier that regulates the movement of substances in and out of the cell. - Proteins:
Membrane proteins are integral or peripheral. Integral proteins span the bilayer, serving functions like transport of molecules, acting as receptors, or enzymatic activity. Peripheral proteins are loosely attached to the surface of the membrane and play roles in signaling and maintaining the cell’s shape. - Fluidity:
The “fluid” aspect refers to the dynamic movement of phospholipids and proteins within the bilayer, allowing the membrane to be flexible, repair itself, and allow certain molecules to pass through. Factors such as temperature and cholesterol content can influence this fluidity.
In summary, the fluid mosaic model depicts the membrane as a flexible, dynamic structure where proteins are embedded in or associated with a fluid phospholipid bilayer, contributing to a variety of cellular processes like transport, communication, and enzymatic activities.