1. In which one of the following groups, all the three are examples of polysaccharides ?
a) starch, glycogen, cellulose b) sucrose, maltose, glucose c) glucose, fructose, lactose d) galactose, starch, sucrose
Answer
a) starch, glycogen, cellulose
2. There are many reasons polymers are so important in biology. Which is not a correct reason ?
a) polymers give structural strength
b) polymers are more compact than small molecules
c) polymers often require little energy to assemble or disassemble
d) polymers are more chemically reactive than small molecules
Answer
d) polymers are more chemically reactive than small molecules
3. What type of bond is formed between two monosaccharides ?
a) peptide bond b) hydrogen bond c) ionic bond d) glycosidic bond
Answer
d) glycosidic bond
4. An unknown plant-based food contains insoluble carbohydrate and reducing sugar. When iodine solution was applied to it, the color remained yellowish-brown. Explain this result.
Answer
As this is a plant-based food, it will not contain glycogen, since glycogen is normally produced by animals as a storage molecule. The insoluble carbohydrate could be cellulose, which gives a negative result with iodine. Some plant-based foods, especially vegetables, may have a waxy cuticle layer that prevents iodine from entering the starch grains present in the food. Sodium hydroxide is not required for the iodine test for starch.
5. Five disaccharides were each hydrolysed with dilute acid and the purified products were separated by chromatography. The results are shown in the figure below. Spot 1 represents the products obtained from the hydrolysis of sucrose. Which of the following represents the results obtained from the hydrolysis of lactose and maltose ?
Answer
Sucrose is made up of a glucose molecule and a fructose molecule while maltose is made up of two glucose molecules. Since maltose and sucrose both have glucose in its structure, maltose will likely be spot 3. Lactose is made up of glucose and galactose. Since spot 3 shows glucose from the separation of maltose, lactose can only be spot 2 which shows glucose and one other sugar in its separation.
6. What macromolecule is chitin ?
a) a nitrogen containing polysaccharide
b) a phosphorus containing polysaccharide
c) a sulphur containing polysaccharide
d) a simple polysaccharide
Answer
a) a nitrogen containing polysaccharide
7. The figure below shows three types of polymers, 1, 2 and 3, which can be formed by units of glucose. Which of these polymer(s) is/are found in animal storage organs ?
a) 1 only b) 2 only c) 1 and 3 d) 2 and 3
Answer
b) 2 only
8. Each of the polymers above is tested with iodine solution. Which row shows the correct observation ?
a) 1 = blue-black, 2 = blue-black, 3 = blue-black
b) 1 = blue-black, 2 = yellow-brown, 3 = yellow-brown
c) 1 = yellow-brown, 2 = blue-black, 3 = yellow-brown
d) 1 = yellow-brown, 2 = yellow-brown, 3 = blue-black
Answer
b) 1 = blue-black, 2 = yellow-brown, 3 = yellow-brown
9. Animals generate more energy from glucose in the presence of oxygen, than in the absence of oxygen. This is because oxygen:
a) is needed as an oxidising agent to fully break down glucose
b) binds to the enzymes which break down glucose
c) neutralises acids made by breaking down glucose
d) is needed as a reducing agent to fully break down glucose
Answer
a) is needed as an oxidising agent to fully break down glucose