Samples of a food were tested using Benedict’s reagent, biuret solution and ethanol. After testing, the solutions were blue with Benedict’s reagent, purple with biuret and cloudy with ethanol. Which molecules do the samples contain?

Which statement is true for cellulose, but not true for protein?

Which statement describes how the molecular structure of starch is suited to its function?

Which linkages are found between the glucose units in cellulose?

Water is important to living organisms because it

Which of the statements about polysaccharides can be used to describe both amylopectin and cellulose?

1 adjacent glucose molecules are rotated by 180°

2 contains 1,4 glycosidic bonds

3 polymer of α–glucose

Glycogen is a polymer of glucose. Which description summarises its structure?

Four students, 1, 2, 3 and 4, each carried out the reducing sugar test and the non-reducing sugar test on a sucrose solution.

Which observations demonstrate that they carried out the correct tests?

What occurs when sucrose is broken down to monosaccharides?

One naturally occurring polysaccharide is an unbranched chain of the molecule acetylglucosamine linked by β-1, 4 glycosidic bonds. There are –CH₂OH groups that alternate on each side of the polysaccharide chain.

Many hydrogen bonds form between these unbranched chains.

Which polysaccharide has a structure similar to that described?

Why may fish living in ponds survive temperatures below 0°C in winter?

Which feature of water is least likely to affect the life of an animal in a tropical rain forest?

A naturally occurring polysaccharide is a branched chain of α-glucose. The straight parts of the molecule are linked by α-1, 6 glycosidic bonds with a small number of branches which are linked by either an α-1, 3 glycosidic bond or an α-1, 4 glycosidic bond.

Which polysaccharide has a structure most similar to that described?

The molecule shown is a polymer of reducing sugars.

Which procedures could be carried out in order to test for the presence of the reducing sugars in this molecule?

1 Add hydrolytic enzyme and then heat with Benedict’s reagent.

2 Dissolve in water, neutralise and then heat with Benedict’s reagent.

3 Boil with hydrochloric acid, neutralise and then heat with Benedict’s reagent.

Which comparative statements concerning biological molecules are correct?

1 A collagen molecule is a fibrous protein that contains many amino acids with hydrophobic R-groups whereas a haemoglobin molecule is a globular protein with no amino acids with hydrophobic R-groups.

2 Sucrose hydrolysis results in glycosidic bond breakage and the production of equal proportions of fructose and α-glucose molecules, whereas cellulose hydrolysis results in only β-glucose molecules.

3 The glycosidic bonds of glycogen have been formed between two α-glucose molecules, whereas with amylopectin, the bonds have been formed between an α-glucose molecule and a β-glucose molecule.

Ethylene glycol is a chemical used to prevent water from freezing. If ethylene glycol is swallowed accidentally, it is metabolised by an enzyme found in liver cells to produce a toxic product. The enzyme normally catalyses the oxidation of ethanol to a harmless product. People who have swallowed ethylene glycol are treated with large doses of ethanol. This prevents formation of a toxic product and allows the body to excrete the ethylene glycol.

Which statement describes why this treatment works?

The statements are about the properties of water.

1 It requires a lot of heat to evaporate.

2 It retains a lot of heat.

3 It is able to form hydrogen bonds with other water molecules.

4 It is able to form hydrogen bonds with other polar and non-polar molecules.

Which properties are important in transpiring plants to prevent enzymes in leaves from being

denatured?

Which description is correct?

Polar molecules form hydrogen bonds with each other. Which properties of water result from its molecules being polar?

1 good solvent

2 high specific heat capacity

3 high surface tension

4 cohesive

Which properties of water are a result of only cohesion?

1 The water has a high surface tension.

2 Water moves up xylem vessels.

3 Water is an excellent solvent.

Chitin is a polysaccharide consisting of long straight chains of the monosaccharide acetylglucosamine, linked by 1,4 glycosidic bonds. Acetylglucosamine is similar in structure to glucose, but contains nitrogen, allowing hydrogen bonds to form between adjacent chains of chitin when they lie parallel to each other.

Which polysaccharide is most similar in structure to chitin?

The diagram shows the relationship between different polysaccharides and the glycosidic bonds formed between the monomers.

Bacterial cells divide by a process called binary fission. Which macromolecules must be synthesised for binary fission?

1 cell membrane proteins and RNA

2 DNA and peptidoglycan

3 enzymes and cellulose

Which statements about both amylose and amylopectin are correct?

1 They are polymers.

2 They are formed by hydrolysis reactions.

3 They are linear molecules.

4 They contain α-1,4 glycosidic bonds.

When a lake begins to freeze, which properties of water are needed for fish to survive?

1 Water has a high surface tension.

2 Water has a high latent heat of vaporisation.

3 Water has a high thermal capacity.

4 Water has its maximum density at 4°C.

In order to estimate the quantity of glucose in a solution, equal volumes of a range of known concentrations were mixed with equal excess volumes of Benedict’s solution and placed in a thermostatically controlled water-bath at 90°C for the same length of time.

The unknown solution was then treated in the same way and the colours of the known and unknown solutions compared. What is the independent variable in this procedure?

The diagram shows how the β-glucose units of cellulose are linked to each other.

What is the significance of the fact that the OH groups on carbon 2 in adjacent glucose molecules are on opposite sides of the molecule?

A student carried out the Benedict’s test on four different concentrations of glucose solution and then recorded the time taken for the first appearance of a colour change (the end-point).

The student found it difficult to identify the first appearance of a colour change and consistently timed each solution for two seconds after it had appeared. This introduced a source of error into the experiment.

Which statements about this error are correct?

1 The effect of the error will be reduced if the student performs three repeats at each concentration of glucose.

2 The error will prevent the student from identifying which solution has the highest concentration of glucose.

3 The error is systematic as the student consistently timed each solution for two seconds after the end-point.

Which two polysaccharides both have 1,6 glycosidic bonds and are branched?

Which features adapt a cellulose molecule for its function?

1 Long chains of glucose molecules coil into a helix.

2 Many hydrogen bonds form between adjacent chains.

3 It is insoluble in water.

A student carried out four tests for biological molecules on a sample of milk. The tests and their results were as follows.

● Heating to 80 °C with Benedict’s solution gave a green colour.

● Adding Biuret solution gave a purple colour.

● Adding iodine solution gave an orange colour.

● Boiling with acid, followed by neutralisation, then heating to 80 °C with Benedict’s solution gave a brick red colour.

Which conclusion about these results is correct?