Question

Microfibrils are composed of
(A) HemiceLlulose
(B) Cellulose
(C) Peptidoglycans
(D) Lignin

Answer 1

Hint: Microfibrils are fiber-like strands composed of glycoprotein and an organic compound which is a polysaccharide consisting of a linear chain of several hundred to many thousands of β linked D-glucose units.

Complete answer:
A microfibril is a very fine fibril, consisting of glycoproteins and cellulose. Cellulose microfibrils are present in the inner surface of the primary cell wall. Even the term microfibril is used as a general term in describing the structure of protein fiber, e.g. hair and sperm tail. When the plant cell absorbs the water, the volume of the cell increases, and the microfibrils which were existing earlier, separate, and the new ones are formed to help increase cell strength.
So, the correct answer is ‘Cellulose’.

Additional Information: Cellulose is synthesized by cellulose synthase or Rosette terminal complexes that reside on a cell membrane. As soon as the cellulose fibrils are synthesized and grow extracellularly they push up against neighboring cells. Since the neighboring cell can't move easily the Rosette complex is instead pushed around the cell through the fluid phospholipid membrane. Eventually, this leads to the cell becoming wrapped into a microfibril layer. This layer becomes the cell membrane. The organization of microfibrils forming the first cell wall is quite disorganized. However, another mechanism is employed in secondary cell walls resulting in its organization. Essentially, lanes on the secondary cell wall of the plant are built with microtubules. These lanes force microfibrils to stay in a very certain area while they wrap. During this process, microtubules can spontaneously depolymerize and depolymerize during a different orientation. This results in a unique direction within which the cell continues getting wrapped.
Note: Microfibrillar angle is defined as the angle microfibrils make with respect to the fiber axis. It is concluded that the microfibrillar angle is the main parameter that affects the inherent fiber strength properties.