Why is it impossible for humans to digest food that contains...

Why is it impossible for humans to digest food that contains cellulose? a. There is no energy available in fiber. b. An inactive form of cellulase in human digestive tract renders it undigested and removes it as waste. c. The acidic environment in the human stomach makes it impossible to break the bonds in cellulose. d. Human digestive enzymes cannot break down the $\beta-1,4$ glycosidic linkage in cellulose, which requires a special enzyme that is absent in humans.

Why is it impossible for humans to digest food that contains cellulose?
a. There is no energy available in fiber.
b. An inactive form of cellulase in human digestive tract renders it undigested and removes it as waste.
c. The acidic environment in the human stomach makes it impossible to break the bonds in cellulose.
d. Human digestive enzymes cannot break down the $\beta-1,4$ glycosidic linkage in cellulose, which
requires a special enzyme that is absent in humans.

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Key Concepts

Cellulose

Cellulose is a complex carbohydrate that forms the structural framework of plant cell walls. It is composed of long chains of glucose molecules linked by specific beta-1,4 glycosidic bonds, which provide rigidity and resistance to degradation. This structure is fundamentally different from other digestible carbohydrates in the human diet.

Beta-1,4 Glycosidic Linkage

The beta-1,4 glycosidic bond is a type of chemical linkage that connects glucose units in cellulose. Its configuration makes it resistant to hydrolysis by the enzymes present in the human digestive system, which are typically designed to break down alpha bonds found in other carbohydrates like starch.

Digestive Enzyme Specificity

Human digestive enzymes are specialized proteins that catalyze the breakdown of dietary macromolecules. While these enzymes efficiently digest carbohydrates such as starch, they lack the specific enzyme called cellulase, which is required to cleave the beta-1,4 glycosidic bonds in cellulose. This absence means that cellulose passes through the gastrointestinal tract largely undigested.

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