Tag: carbohydrates - definition and classification

Cellulose is a type of carbohydrate, containing chains of glucose rings. The cell walls, which are responsible for providing support and rigidity to the plants are made of cellulose. 

Carbohydrates undergo dehydration in the presence of sulphuric acid, giving aldehyde as a product which undergoes condensation in the presence of Molisch reagent ($\alpha-napthanol $ dissolved in ethanol) to give a purple colored compound. This forms the basis of Molisch test to detect carbohydrates. Since glucose, raffinose, and deoxyribose are all carbohydrates, they can be identified using Molisch reagent

Fehling's solution is used to distinguish between reducing sugars (like glucose) and non-reducing sugars (like sucrose/cane sugar). Glucose will give a positive test (red precipitate), while sucrose will not.

The two forms of D-glucopyranose (alpha and beta) differ only in the configuration at the anomeric carbon (C1). Such isomers are specifically called anomers.

Glucose is a dextrorotatory sugar (rotates plane-polarized light to the right) and is commonly found in fruits, often referred to as grape sugar.

Ribose and deoxyribose sugars commonly exist in furanose form in nucleic acids. Fructose, also known as fruit sugar, exists in furanose form in its cyclic structure.