How do Starch and Cellulose Differ?
I was sipping over steaming coffee in a quaint little cafe with a friend, indulging in conversation. Nutrition started taking its toll, and suddenly, this question generated itself: why cannot humans digest cellulose within plant foods? And so this question led us to then begin to dip further into the interesting world of starch and cellulose. A mystery hidden in the secret of starch, the energy reservoir of plants, and cellulose, the sturdy building block of plant cell walls, continues to shape our understanding of carbohydrates. On this short journey, we unraveled this difference between these two polysaccharides and learned what is the difference between starch and cellulose and hence their roles in our daily lives.
Explain Starch and Cellulose
Definition
Starch: Starch is a polysaccharide consisting only of glucose units that are linked together to form long chains. In plants, starch is considered the most essential energy storage molecule. It acts as a readily available source of fuel for burning. Plants synthesize and store starch in various parts, including seed, roots, and tubers. Starch is one of the common types found in a wide variety of plant-based foods: grains, in general, like wheat, rice, and corn; potatoes; legumes, which include beans and lentils; and starchy vegetables. Starch is broken into individual glucose molecules during digestion by starch-digesting enzymes, and these can then be absorbed and used as energy by animals as well as humans.
Cellulose: Cellulose is a polysaccharide which comprises glucose units. However, unlike starch, in cellulose, a long linear chain forms with each glucose unit bonded together through β-1,4-glycosidic bonds. The structure organization leads to the cellulose molecules being tightly packed and hydrophobic hence water-insoluble. Cellulose is the major component of plant cell walls, lending strength, rigidity, and support to the plant cells. It performs a very crucial role in keeping tissues within plants with a general configuration. Since it is also nontoxic and resistant to being digested by most living animals, cellulose has also termed as dietary fibre, which supports a healthy system of gut, and gives proper bowel movement.
What are Starch and Cellulose?
Interesting facts:
Starch: Starch consists of two types. One is amylose, and the other is amylopectin. Amylose has a highly branched chain; however, it is linear. Starch acts as an energy source for all the living beings and animals.
Cellulose: Humans do not have the enzyme that digests cellulose; thus, cellulose in the diet serves as dietary fibre and is passed through the human alimentary canal. However, some animals like cows and termites digest cellulose by the help of specialized microorganisms.
Difference between Starch and Cellulose:
| S.No |
Category |
Starch |
Cellulose |
|
1 |
Structure | Helical arrangement of glucose units. | The linear arrangement of glucose units with hydrogen bonds between chains. |
|
2 |
Function | Energy storage in plants. | Structural support in plant cells. |
|
3 |
Digestibility | Easily digested by humans and animals. | Indigestible in humans. |
|
4 |
Solubility | Soluble in hot water, forms a gel-like substance. | Insoluble in water. |
|
5 |
Uses | Food, paper, and textile industries. | Paper, textile, and biofuel industries. |
Characteristics of Starch and Cellulose
Starch:
Branched Structure: Starch consists of a branched structure, having linear chains known as amylose and highly branched structures that are called amylopectin. This results in easy digestion and rapid glucose release for energy.
Granular Form: In general, starch is granular in form inside the cells of plants, typically a microscopic granule. These granules differ in sizes and shapes depending on the source of starch.
Gelatinisation: Starch has the special property of gelatinization wherein granules of starch absorb water and swell up into a viscous gel-like substance. This property is useful in cooking and food processing, as it thickens sauces, soups, or any other culinary preparations.
Cellulose:
Cellulose, unlike starch, is a linear structure that consists of glucose units bonded together in long chains. This linear arrangement provides cellulose with high tensile strength and rigidity.
This produces yet another arrangement among molecules, long parallel chains held together by hydrogen bonds, which has been called microfibrils; these are part of the structural support and strength that the plant cell wall gets.
Fibre Formation: The cellulose-based fibres are resistant and strong. Hence, they are used widely in various applications. The large quantities of fibres such as cellulose are processed to give fabrics having breathability and moisture absorption.
Summary:
Starch and cellulose are two polysaccharides possessing different structure, function, digestibility, and solubility. The main roles of starch are that this carbohydrate serves as a storage form of energy in the plant system and is easily digestible. In contrast, cellulose is mainly used for structural purposes for all kinds of cells of higher plants and it is not digestible in humans. Both of them have vital applications in various industries. There are innumerable differences between starch and cellulose; however, we tried a few in this article.
