Final answer:
The correct answer is option a. The major component of the plasma membrane of a plant cell is phospholipids, which form a protective barrier regulating the passage of substances in and out of the cell.
Step-by-step explanation:
The major component of the plasma membrane of a plant cell is phospholipids. These molecules form the basic structure of the membrane, organizing themselves into a bilayer that creates a barrier between the internal and external environments of the cell. The phospholipid bilayer is crucial in regulating the passage of substances in and out of the cell, ensuring that essential compounds enter while preventing harmful materials from causing damage.
Phospholipids are composed of two fatty acid chains, a glycerol backbone, and a modified phosphate group. This structure allows them to be amphipathic, meaning they have both hydrophobic (water-hating) and hydrophilic (water-loving) properties, which enables them to form a barrier that is selectively permeable to different substances.While components like cellulose fibers, collagen fibers, and pectins play significant roles in the plant cell structure, especially in the cell wall, it is the phospholipids that form the fundamental structure of the plasma membrane.