Cellulose ans starch both are needed to fulfill the energy requirements of our body. Moreover, they belong to the same group of carbohydrates. The have high molecular weight. The main difference between cellulose and starch is, cellulose is the polymeric form of glucose which has glucose units linked by glycoside linkage. But on the other hand, starch is a polymeric form of glucose which is linked by alpha 1,4 linkage. The both differ in their chemical and physical properties.
What is Starch?
In terms of composition, cellulose is similar to starch. They are polymeric form of glucose molecules which are linked by 1,4 linage. The chain of glucose molecules which forms the starch could be linear, mix or branched. It depends on the site or source of where it is stored and starch is the storage form of carbohydrate. Properties of starch can vary from to another depending on the source or site where it is stored. The properties of starch even depends upon the nature and number of of alpha 1,4 glycosidic bonds. There are two forms of starch Amylase and Amylopectin. Amylopectin is complex and branched form while amylose is the simpler linear form and starch is the mainly a storage polysaccharide.
What is Cellulose?
Cellulose is the most common organic molecule and major structural unit of plants. It is made up of glucose units which are joined together by glycoside linkage. It forms beta 1,4 linkages because beta bond is formed between first and fourth carbon of the next glucose unit. Cellulose is made up of 4000-8000 units of glucose. There are two forms of cellulose Hemicellulose and Lignin. Cellobiose is also one of the forms of cellulose but it results from hydrolysis of cellulose and is a disaccharide. Cellulose is hydrolyzed by the enzyme known as cellulase.
Key Differences between Starch and Cellulose
- The difference is in the linkage of the glucose bonds.
- Cellulose has beta 1,4 linkage while starch has alpha 1,4 linkage.
- Cellulose is a structural polysaccharide while starch is mainly a storage polysaccharide.
- Cellulose occurs in nature as pure cellulose, lignin or hemicellulose. Whereas starch occurs in the form of amylopectin and amylose.
- Starch is acted upon by amylases and cellulose by cellulase.
- Starch can be broken down to maltose and then to glucose. Cellulose on the other hand, cannot be easily digested by the help of an enzyme cellulase.
- Cellulose owes its rigidity to so many hydrogen bonds in the structural integrity of this molecule. This makes it a good and rigid structural polysaccharide.