Reasons Why Humans Cannot Digest Cellulose
Humans lack the ability to digest cellulose for several reasons:
- Lack of Cellulase Enzyme: Cellulose is a complex carbohydrate composed of glucose units linked together by beta-1,4-glycosidic bonds. Humans do not produce the enzyme cellulase that is needed to break down these linkages and hydrolyze cellulose into individual glucose molecules.
- Lack of Specialized Digestive Structures: Humans have a monogastric digestive system (single-chambered stomach) whereas ruminant animals have multi-chambered stomachs. Humans lack the specialized chambers and microbial populations important for efficient digestion of cellulose.
- Complex Structure of Cellulose: The beta-1,4-glycosidic linkages in cellulose are resistant to hydrolysis by human digestive enzymes, making cellulose indigestible in the human stomach and small intestine.
- Limited Fermentation in the Colon: Certain gut bacteria break down cellulose to some extent in the human colon. But the fermentation in the colon is limited, and the byproducts, such as short-chain fatty acids, are not as efficiently absorbed and utilized for energy as the breakdown of other carbohydrates.
Also Read: Disorders Of Digestive System
Cellulose In Digestion – Herbivores, Termites, & Ruminants
Cellulose is a type of fiber that cannot be digested by the human digestive system. The presence of beta-acetal linkages in cellulose distinguishes it from starch and determines its digestion. The organisms that are capable of digesting the cellulose with their cellulase enzyme are microorganisms such as bacteria, fungi, and protozoa.
Except for a few multicellular organisms, such as termites, most higher organisms cannot digest cellulose without the help of microorganisms. In this article, we will discuss cellulose in digestion and why humans can digest starch but not cellulose.
Table of Content
- What is Cellulose?
- Structure of Cellulose
- Cellulose Digestion in Ruminants
- Cellulose Digestion in Termites
- Cellulose Digestion in Herbivores
- Reasons Why Humans Cannot Digest Cellulose
- Importance of cellulose in digestion