Key difference - amylose vs. cellulose

Starch is a carbohydrate component that is classified as a polysaccharide. Ten or more monosaccharide units are linked by glycosidic bonds to form polysaccharides. Because polysaccharides are larger molecules, they have a larger molecular weight, characteristically greater than 10,000. In addition, some polysaccharides are made up of a single monosaccharide unit and are referred to as homopolysaccharides . On the other hand, some polysaccharides consist of a mixture of monosaccharide units and are called heteropolysaccharides . Amylose and cellulose are two of the most important and abundant homopolysaccharides in the world. Amylose is a storage polysaccharide in which D-glucose molecules are linked by an α-1,4-glycosidic bond to form a linear structure called amylose. In contrast, cellulose is a structural polysaccharide in which D-glucose molecules are linked by β (1 → 4) glycosidic bonds to form a linear structure called cellulose. This is the main difference between amylose and cellulose . This is the main difference between amylose and cellulose. In this article, let's work out the difference between amylose and cellulose in terms of their uses, chemical and physical properties.

What is amylose?

Amylose is a linear polysaccharide with D-glucose units linked together to form this structure. A large number of glucose molecules, ranging from 300 to several thousand, can be involved in the development of an amylose molecule. Typically, the number 1 carbon atom of one glucose molecule can form a glycosidic bond with the 4th carbon atom of another glucose molecule. This is called the α-1,4-glycosidic linkage, and as a result of this linkage, amylose has acquired a linear structure. Also, it's a tightly packed molecule and they don't have any branches. Amylose is insoluble in water and therefore serves as a food or energy store in plants. It can be digested by human intestinal enzymes and is broken down into maltose and glucose during digestion, which can be used as a source of energy.

The iodine test serves to differentiate between amylose and starch and during the test the iodine molecules are fixed in the helical structure of the amylase; as a result, it gives a dark purple / blue color. In general, amylose makes up 20-30% of the starch structure, the rest is amylopectin. In addition, amylose is more resistant to digestion than amylopectin and is therefore crucial for lowering the glycemic index value and for the formation of resistant starch, which is considered an active prebiotic.

Iodine test of wheat starch through a light microscope.

What is cellulose?

Cellulose was first discovered in 1838 by the French chemist Anselme Payen. Payen isolated them from plant material and determined their chemical formula. It is a structural polysaccharide with D-glucose units linked together to form this structure. A large number of glucose molecules such as 3000 or more can take part in the development of a cellulose molecule. In cellulose, glucose molecules are linked by β (1 → 4) -glycosidic bonds and do not branch. It is therefore a straight chain polymer. In addition, it can develop a very rigid structure due to the hydrogen bonds between glucose molecules. It is not soluble in water. It is abundant in the cell walls of green plants and in algae and thereby gives the plant cells strength, rigidity, strength and shape. Cellulose in the cell wall is permeable to every component; thus it enables the passage of constituents into and / or out of the cell. Cellulose is considered to be the most abundant and abundant carbohydrate on earth. It is also used to make paper, biofuels, and other beneficial by-products.

Cotton fibers are the purest natural form of cellulose

Difference Between Amylose and Cellulose

The difference between amylose and cellulose can be broken down into the following categories. They are;

definition

Amylose is a linear-helical carbohydrate polymer made of α-D-glucose units and is considered a storage polysaccharide.

Cellulose is an organic polysaccharide with a linear chain and is considered a structural polysaccharide.

Chemical structure

Amylose :

Cellulose :

Structure and number of monomer units

Amylose is a linear polymer with 300 to several thousand repeated glucose subunits.

Cellulose is a straight-chain polymer with 3000 to several thousand repeated glucose subunits.

Crystalline and amorphous areas

Amylose consists of crystalline and amorphous areas. However, amylose goes down when heated in water to about 60-70 ° C, e.g. B. when cooking, from crystalline to amorphous.

Although cellulose consists of crystalline and amorphous areas, cellulose has more crystalline areas compared to amylose. In order to convert crystalline to amorphous areas, cellulose needs a temperature of 320 ° C and a pressure of 25 MPa.

chemical formula

Amylose does not have an exact formula and is variable.

Cellulose formula is (C ₆ H ₁₀ O ₅ ) _n

Glycoside bonds

Amylose : α (1 → 4) glycosidic bonds

Cellulose : β (1 → 4) -linked D-glucose units

Function in the plant

Amylose plays an important role in plants' energy storage and is less susceptible to digestion than amylopectin. Therefore it is the preferred starch for storage in plants. It accounts for around 20-30% of the stored starch.

Cellulose is a major structural carbohydrate found primarily in the cell wall of green plants. But it also occurs in many forms of algae and the Oomycetes. It is the most abundant organic polymer on earth.

Identification assay

The iodine test is used to detect amylose . Iodine molecules fit into the helical structure of the amylose and form a blue-black color complex. Amylose can be qualitatively identified using this blue-black color. To quantify the amylose content, the absorbance of the developed color can be measured with a UV / VIS spectrophotometer.

Anthrone test is used to identify cellulose . Cellulose reacts with anthrone in sulfuric acid and the resulting colored compound is measured with a UV / VIS spectrophotometer at a wavelength of approximately 635 nm.

Other uses

Amylose is used in the following industrial and food-based applications.

Thickener

Water binding agent

Emulsion stabilizer

Gelling agent

Cellulose is used in both industrial and food-based applications below.

Cardboard and paper manufacture

Manufacture of pulp and cardboard

Manufacture of cotton, linen and other vegetable fibers (they are the main component of textiles)

Cellophane and Viscose, also known as the manufacture of regenerated cellulose fibers

Edible microcrystalline cellulose (E number - E460i) and powdered cellulose (E number - E460ii) are used as inactive fillers in drug tablets and also act as thickeners and stabilizers in processed foods

It is used as a stationary phase for thin layer chromatography in the laboratory.

Biofuel production

digestion

Amylose can be digested by humans because humans have salivary or pancreatic amylase to digest amylose.

Cellulose cannot be digested by humans because the human intestinal tract does not produce enzymes to break β (1 → 4) -glycosidic bonds. However, microorganisms in the colon can break down cellulose and produce organic acids and gases. In addition, cellulose acts as fiber and can absorb moisture in the intestinal tract, preventing constipation and making it easier to defecate easily. However, ruminants and termites can digest cellulose with the help of symbiotic gut microorganisms that live in their rumen.

In summary, cellulose and amylose are primarily carbohydrates and are considered to be the most abundant polysaccharides in the world. However, due to their different physical and chemical properties, they have different functions in the plant.

References:

Cohen, R., Orlova, Y., Kovalev, M., Ungar, Y. and Shimoni, E. (2008). Structural and functional properties of amylose complexes with genistein. Journal of Agricultural and Food Chemistry, 56 (11): 4212-4218.

Nelson, D. and Michael, MC Principles of Biochemistry. 5th ed. New York: WH Freeman and Company, 2008.

Nishiyama, Y., Langan, P. and Chanzy, H. (2002). Crystal structure and hydrogen bridge system in cellulose Iβ from synchrotron X-ray and neutron fiber diffraction. Jam. Chem. No. Soc, 124 (31): 9074-82.

Richmond, TA and Somerville, CR (2000). The cellulose synthase superfamily. Plant Physiology, 124 (2): 495-498.

Image courtesy:

"Wheat starch granules" by Kiselov Yuri - own work. (Public Domain) via Commons

"Cotton" from KoS - own work. (Public Domain) via Commons

“Amylose3” by NEUROtiker - own work. (Public Domain) via Wikimedia Commons

“Cellulose armchair ” by NEUROtiker - own work. (Public Domain) via Commons