Polymers

Cellulose

Cellulose is a specific type of molecules which is consisting of hundreds or even thousands of carbon, hydrogen and oxygen atoms. Cellulose is the kind of main substance that can be found in the walls of plant cells. It is helping plants to remain stiff and upright. Although we cannot digest cellulose, still it is important in the diet in the form of fibre. For example, cellulose is present in the ratio of 30% in a tree which can be made into paper.

Actually, it is a kind of polysaccharide having the molecular formula \(C_{6}H_{10}O_{5})_{n}\), which is composed of glucose monomers. It is very useful in the manufacture of numerous products such as paper, textiles, pharmaceuticals, and insulation. Some other names of Cellulose are cellulose ester, fibre, paper, cellulosic, fibre.

Cellulose

                                                                                                      Cellulose

Introduction to Cellulose

Cellulose is being considered the most abundant organic compound on the earth. The chemical formula of cellulose as a chain is \(C_{6}H_{10}O_{5})_{n}\). Actually, it is a complex carbohydrate that consists of oxygen, carbon, and hydrogen. It is a chiral, tasteless compound without any odour. It was first discovered by French chemist Anselme Payen in the year 1838. Cellulose is a kind of organic compound that is water-soluble as well as biodegradable.

During the year 1890, it was being used to produce the first thermoplastic termed celluloid. In natural cotton, the amount of cellulose present is 90%. Also, the amount of cellulose present in the wood is 40-45% and in dried hemp, it is 57%. Cellulose is a popular example of polysaccharide and useful for structural function in plants. Cellulose is the unbranched kind of glucose, which is residue polymer put together via beta-1,4 connections. Hence, it enables the molecule to form long, straight chains.

Carbohydrates and Polysaccharides

These are the active polyhydroxy aldehydes or ketones, which are producing such units on the hydrolysis. These are mainly produced by plants like cane sugar, starch, glucose, cellulose etc. The major classification of carbohydrates are as follows:

  1.  Monosaccharides: Carbohydrates that cannot be hydrolyzed further to give simple units of polyhydroxy aldehydes or ketones. For example glucose, fructose, ribose.
  2. Oligosaccharides: Carbohydrates that yield 2 to 10 monosaccharide units on the hydrolysis. Depending upon the unit number of monosaccharides these are further classified into disaccharides, trisaccharides, etc. For example Sucrose, maltose.
  3. Polysaccharides: Carbohydrates that yield a large number of monosaccharide units on the hydrolysis. For example Starch, cellulose, glycogen.

Polysaccharides are containing a large number of monosaccharide units, which are joined together by the glycosidic linkage.

  1. Starch: It is the main storage polysaccharide of the plants. It is a polymer of alpha- Glucose and consist of two components: Amylose and Amylopectin.
  2. Amylose: These are the water-soluble component, having about 15-20% of the starch.
  3. Amylopectin: These are insoluble in water and are constituting about 80-85% of the starch.
  4. Cellulose: These are occurring in plants and the most abundant organic substance. It is a straight-chain polysaccharide composed of Beta-D-glucose units joined by the glycosidic linkage.
  5. Glycogen: These are the carbohydrates, which are stored in the animal body as glycogen. These are also termed animal starch because their structure is similar to amylopectin. It is also present in the liver, muscles and brain.

Synthesis of Cellulose

Its synthesis is mainly limited to plants and bacteria, with some specific animals.

  1. Plants: In the plants, cellulose synthesis is taking place on special complexes present at the cell membrane, which are known as rosette terminal complexes. These complexes are some kind of hexameric transmembrane proteins, which are capable of free floatation in the plasma membrane. These are containing at least three cellulose synthase enzymes. These transmembrane rosettes are performing two functions:- polymerization of glucose residues to form the cellulose chain and assembly of the cellulose microfibrils.
  2. Bacteria: Bacteria are using the same family of enzymes for cellulose synthesis as in the case of plants. But, the bacterial enzymes are encoded by different type of genes. Another such hypothesis says that plants are acquiring the cellulose synthesis enzymes from bacteria after the endosymbiosis process.
  3. Animals: Cellulose can also be synthesized by some animals known as tunicates. These animals are invertebrate animals and found in the sea. They are having a hard shell that encloses the delicate body of the animal. Cellulose can be extracted from the shell of these animals.

Properties of Cellulose

Cellulose is different from the rest kind of polysaccharides. The unique property of cellulose is due to its unique structure. These properties are also depending on the number of glucose subunits present in it. Some of its properties are as follows:

  1. Cellulose is the crystalline solid which have a white powdery appearance
  2. It has high tensile strength because of the firm hydrogen bonds, present between the individual chains in cellulose microfibrils. Such tensile strength of cellulose microfibrils is very much similar to that of steel.
  3. Its alternate arrangement of molecules also contributes to the high tensile strength.
  4. It is soluble in organic solvents, whereas not soluble in water.
  5. Its many properties are depending upon the degree of polymerization or chain length and the number of glucose molecules.
  6. Cellulose has no taste, no odour. It is chiral and biodegradable too.

Physical Properties

  1. Its molar mass is 162.1406 gram per mole.
  2. Its density is 1.5 gram per cubic cm.
  3. Its melting point is 260-270 degrees C.

Chemical Properties

  1.  It is having a strong affinity to itself and materials containing hydroxyls mainly water.
  2. It is very much reactive to water. Water molecular smallness promotes those reactions with the cellulose chains and as a result immediately forming hydrogen bonds.
  3. At the high temperature, it can be broken down into glucose by treating with the concentrated minerals acids.
  4. It is more crystalline in nature in comparison to starch.

Uses of the Cellulose

  1. Cellulose is mainly useful in paperboard and paper production. Its smaller amounts are converted into its derivatives like cellophane and rayon.
  2. It is useful as a fibre supplement in our diet.
  3. Also, it helps as an additive in various food items.
  4. It is useful as a preservative in cheese as it plays the role of an anti-clumping agent.
  5. Cellulose is useful for making explosives and for the manufacturing of nitrocellulose.
  6. It is useful as a stationary phase in chromatography.

 FAQs about Cellulose

Q.1: What kind of foods contain cellulose?

Answer: Cellulose is the insoluble dietary fibre, consisting of glucose polymers present in all kind of cell walls of plants. Foods like leafy green vegetables, such as kale, sprouts from Brussels and green peas are containing cellulose.

Q.2: What is the cellulosic material?

Answer: Cellulosic materials are providing the structure to plants and strength to the stems. Cellulose and hemicellulose, together known as cellulosic materials. It can be broken down into sugars, which further can be fermented into ethanol.

Q.3: What is the richest source of cellulose?

Answer: Green beans are the richest in cellulose and hemicellulose. On a wet-weight basis, fresh apples and peaches and canned carrots and frozen potatoes are having a higher ratio of it.

Q.4: Can we digest cellulose?

Answer: No, we cannot digest cellulose because they lack the enzymes essential for breaking the beta-acetyl linkages. Therefore, the undigested cellulose acts as fibre that aids in the functioning of the intestinal tract in our body.

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