Polysaccharides: Long Chains of Sugars
Polysaccharides are the carbohydrate macromolecules of the acid insoluble pellet — long chains of sugars built from repeating monosaccharide units. In this quiz you will explore how a single building block, glucose, gives rise to strikingly different materials: cellulose for structure, starch for plant energy storage, and glycogen for animal energy release.
What you will practise
- Defining polysaccharides and recognising homopolymers such as cellulose
- Distinguishing starch, glycogen and inulin by their monomer units
- Identifying the reducing and non-reducing ends of a chain
- Explaining the helical structure of starch and the blue starch–iodine colour
- Describing complex polysaccharides such as chitin and its amino-sugar building blocks
Each question is designed to test understanding of molecular architecture rather than isolated facts. Read each option carefully — the distractors are close in meaning.
Q1. Polysaccharides are best described as:
Polysaccharides are long chains of sugars, described in the lesson as threads (literally a cotton thread) containing different monosaccharides as building blocks.
Q2. Cellulose is classified as a homopolymer because it consists of:
Cellulose is a polymeric polysaccharide consisting of only one type of monosaccharide, i.e. glucose, and is therefore a homopolymer.
Q3. In plant tissues, starch functions mainly as:
Starch is described as a variant of cellulose but present as a store house of energy in plant tissues.
Q4. The polysaccharide that serves as an energy variant in animals is:
Animals have another variant called glycogen, which is the animal energy storage polysaccharide.
Q5. Inulin is a polymer of:
The lesson states plainly that inulin is a polymer of fructose.
Q6. In a polysaccharide chain such as glycogen, the right end is called the:
In a polysaccharide chain (say glycogen), the right end is called the reducing end and the left end is called the non-reducing end.
Q7. Which statement about the two ends of a glycogen chain is correct?
The right end is the reducing end and the left end is the non-reducing end of the chain.
Q8. Starch forms helical secondary structures. This helix is significant because it:
Starch forms helical secondary structures and can hold ##\ce{I2}## molecules in the helical portion, giving the blue starch–iodine colour.
Q9. The blue colour observed when starch is treated with iodine is due to:
The starch–##\ce{I2}## complex is blue in colour; the iodine molecules are held within the helical portion of starch.
Q10. Cellulose cannot give the blue colour with iodine because it:
Cellulose does not contain complex helices and hence cannot hold ##\ce{I2}## molecules, so no blue colour appears.
Q11. Plant cell walls are made of:
The lesson states that plant cell walls are made of cellulose, and that paper from plant pulp and cotton fibre is cellulosic.
Q12. The exoskeletons of arthropods contain a complex polysaccharide called:
Exoskeletons of arthropods have a complex polysaccharide called chitin.
Q13. The building blocks of complex polysaccharides such as chitin include:
Complex polysaccharides have as building blocks amino-sugars and chemically modified sugars, for example glucosamine and N-acetyl galactosamine.
Q14. Which pair correctly matches a polysaccharide with its monosaccharide building block?
Inulin is a polymer of fructose, while cellulose consists of only glucose; the other pairings contradict the lesson.
Q15. Which group of macromolecules, together with polysaccharides and polypeptides, makes up the true macromolecular fraction of any living tissue or cell?
Together with polysaccharides and polypeptides, polynucleotides (nucleic acids) comprise the true macromolecular fraction of any living tissue or cell.