Q.50 Which one of the following commercially important carbohydrates is naturally
produced only by the members of the plant kingdom?
(A) Cellulose
(B) Pectin
(C) Chitin
(D) Starch

Pectin is the correct answer. This commercially important carbohydrate is naturally produced exclusively by plants, distinguishing it from the other options which occur in multiple kingdoms.

Option Analysis

Cellulose serves as a primary structural component in plant cell walls but bacteria like Gluconacetobacter xylinus, certain algae, fungi, and even some animals (tunicates) also synthesize it naturally.​

Pectin, a heteropolysaccharide rich in galacturonic acid, forms part of plant primary cell walls and middle lamellae, aiding cell adhesion and found mainly in fruits like citrus and apples; no natural production occurs outside plants.​

Chitin, a nitrogen-containing polysaccharide, builds fungal cell walls and arthropod exoskeletons (e.g., insects, crustaceans), with no plant production.​

Starch functions as the main energy storage polysaccharide in plants but analogous forms like glycogen appear in animals and some microbes.​

Pectin stands out as the carbohydrate naturally produced only by plants among commercially vital options like cellulose, pectin, chitin, and starch. This makes it essential for exams like CSIR NET Life Sciences.

Sources Across Kingdoms

• Cellulose: Dominant in plant cell walls for rigidity, but bacteria (G. xylinus), algae, oomycetes, slime molds, and tunicates produce it too.​

• Pectin: Exclusive to plants, concentrated in dicot cell walls (e.g., citrus peels, apples); synthesized in Golgi from UDP-galacturonic acid.​

• Chitin: Fungi (cell walls) and animals (arthropod exoskeletons) synthesize it via chitin synthase; absent in plants.​

• Starch: Plants store energy as starch granules in plastids; animals use glycogen, fungi store similarly.​

Commercial Relevance

Pectin gels jams and stabilizes foods, extracted from plant waste like apple pomace. Cellulose yields paper and textiles mainly from plants despite other producers. Chitin sources crustacean shells for chitosan in biomedicine. Starch from plants fuels food and industry.​