The key difference between cellulose and starch is that the cellulose is a structural polysaccharide that has beta 1,4 linkages between glucose monomers while the starch is a storage polysaccharide that has alpha 1,4 linkages between glucose monomers.
Starch and Cellulose are macromolecules belonging to the same group of carbohydrates. Carbohydrates are one of the common forms of energy sources in food. They have the molecular formula CH2O. Several monomer units of glucose, interconnected through chemical linkages, make up these macromolecules. Thus, they have a high molecular weight.
What is Cellulose?
Cellulose is the polymeric form of glucose units linked together by glycoside linkages. Therefore, it is the most abundant organic molecule and the major structural unit of plants. Cotton and paper are some forms of pure cellulose. It comprises about 4000-8000 glucose molecules with beta bonds between the 1st C of the first unit and the 4th carbon of the next glucose unit. Thus, it forms beta 1,4 linkages. There are two forms of cellulose such as hemicellulose and lignin.
Moreover, cellobiose is another form, which results from the hydrolysis of cellulose. Thus, it is a disaccharide made of two glucose molecules linked via beta 1,4 linkage. Further, cellulases hydrolyze the cellulose into its monomers.
What is Starch?
Starch is essentially similar to cellulose in the composition. Therefore, they are polymeric forms of glucose molecules linked by alpha 1,4 linkage. The number of molecules making up a starch molecule can vary from 4000 – 8000. The chain of glucose can be either linear, branched or a mix of both depending on the source and site where the form is stored. It is the primary storage form of carbohydrate.
Moreover, starch is a storage form of carbohydrates in plants. Properties of starch can vary from one to another depending on the source from which it is isolated. The properties also depend on the nature of branching and the number of alpha 1,4 glycoside bonds. There are two forms of starch; they are, amylase and amylopectin.
What are the Similarities Between Cellulose and Starch?
- Both are carbohydrates and polysaccharides.
- They comprise with same monomers; glucose.
- Cellulose and Starch have the same glucose based repeating units.
- Both fulfil the energy requirements of our body.
- They have a high molecular weight.
- Cellulose and Starch have a similar composition.
- Starch and cellulose present in plants.
What is the Difference Between Cellulose and Starch?
Although both starch and cellulose are polymeric forms of glucose, they differ in their chemical and physical properties. These differences are mainly attributed to the difference in linkages. Cellulose has beta 1,4 linkages between glucose molecules whereas starch has 1,4 alpha linkages between glucose molecules. This is the key difference between cellulose and starch. Furthermore, the functional difference between cellulose and starch is that the cellulose is a rigid structural polysaccharide while the starch is a storage polysaccharide.
The below infographic tabulates the difference between cellulose and starch with more details.
Summary – Cellulose vs Starch
Although starch and cellulose are both polymeric forms of glucose, they differ in the properties. These differences tend to be the result of the difference of a single chemical bond between the monomeric units. The varied nature makes the carbohydrates to play both energy providing function as well as structural roles. Both cellulose and starch fulfil energy demands of the organisms. However, cellulose plays a structural role while starch plays a storing role. Cellulose has 1,4 beta linkages among the glucose monomers. In contrast, starch has 1,4 alpha linkages. This is the difference between cellulose and starch.