Answer in Brief
Long answer question.
Explain the classes of carbohydrates with examples.
Based on number of sugar units, carbohydrates are classified into three types namely, monosaccharides, disaccharides and polysaccharides.
- Monosaccharides are the simplest sugars having crystalline structure, sweet taste and soluble in water.
- They cannot be further hydrolyzed into smaller molecules.
- They are the building blocks or monomers of complex carbohydrates.
- They have the general molecular formula (CH2O)n, where n can be 3, 4, 5, 6 and 7. e. They can be classified as triose, tetrose, pentose, etc.
- Monosaccharides containing the aldehyde (–CHO) group are classified as aldoses e.g. glucose, xylose, and those with a ketone(–C=O) group are classified as ketoses. E.g. ribulose, fructose.
- Disaccharide is formed when two monosaccharide react by condensation reaction releasing a water molecule. This process requires energy.
- A glycosidic bond forms and holds the two monosaccharide units together.
- Sucrose, lactose and maltose are examples of disaccharides.
- Sucrose is a nonreducing sugar since it lacks free aldehyde or ketone group.
- Lactose and maltose are reducing sugars.
- Lactose also exists in beta form, which is made from β-galactose and β-glucose.
- Disaccharides are soluble in water, but they are too big to pass through the cell membrane by diffusion.
- Monosaccharides can undergo a series of condensation reactions, adding one unit after the other to the chain till a very large molecule (polysaccharide) is formed. This is called polymerization.
- Polysaccharides are broken down by hydrolysis into monosaccharides.
- The properties of a polysaccharide molecule depends on its length, branching, folding and coiling.
- Examples: Starch, glycogen, cellulose.
Concept: Biomolecules in the Cell
Is there an error in this question or solution?