Answer
a. phospholipids
Work Step by Step
One main component of plasma membranes are the phospholipids. These compounds contain a negatively-charged, water-loving head and a nonpolar, hydrophobic tail. When placed into water, these compounds can spontaneously form a double layer where the tails face each other while the heads form a protective layer on the outside.
Cellulose is a component found in the cell wall of plants. Pectin makes up a layer between adjacent plant cells. Collagen fibers are proteins found in the outside environment of the animal cell called the extracellular matrix.
