An example of a polysaccharide is?

1. Analyze the question The question asks which option is a polysaccharide, so we need to know how carbohydrates are classified.

2. Explain the concept Carbohydrates are grouped by the number of sugar units they contain:

• Monosaccharides are single sugar units (simple sugars). Examples: glucose, fructose, galactose, mannose.
• Disaccharides are two monosaccharides joined together. Examples: sucrose, maltose, lactose.
• Polysaccharides are many (hundreds or thousands of) monosaccharide units joined by glycosidic bonds. Examples: starch, cellulose, glycogen.

3. Solution: check each option

• A. Dextrose is another name for glucose, a monosaccharide. ❌
• B. Mannose is a monosaccharide, an isomer of glucose. ❌
• C. Glucose is the basic monosaccharide, C₆H₁₂O₆. ❌
• D. Starch is a long chain of glucose units, (C₆H₁₀O₅)ₙ, found in yam, cassava, rice and maize. ✅

4. Answer Starch is the only polysaccharide listed.

5. Exam tip "Poly" means many. If a carbohydrate name ends in -ose and is a small, sweet, soluble sugar (glucose, mannose, dextrose), it is probably a monosaccharide. The big, non-sweet, insoluble ones to remember as polysaccharides are starch, cellulose and glycogen. Starch, cellulose and glycogen appear again and again in JAMB, so memorize them.