CARBOHYDRATES

Which type of reaction takes place when starch molecules are converted into reducing sugars?

• A condensation

• B hydrolysis

• C polymerization

• D synthesis

A solution of starch is mixed with a solution of amylase. Which reagent should be used to confirm that a reaction had taken place and what would be the appearance of the mixture when the reaction was complete?

• a

• b

• c

• d

The movement of water through the vascular tissue in plants relies on which property of water?

• A changes in density with temperature

• B good solvent for ions and polar molecules

• C high specific heat capacity

• D strong cohesive forces between molecules

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?

• A W, X and Z

• B W, Y and Z

• C W, X and Y

• D X, Y and Z

Lactose is a disaccharide present in the milk of mammals. How will a baby mammal benefit from having this sugar, instead of a monosaccharide, in the milk?

• A Condensation of disaccharides enables rapid production of glycogen.

• B Disaccharides can be transported across membranes for more rapid absorption.

• C Disaccharides have a higher energy value than triglycerides.

• D Hydrolysis of the glycosidic bond gives a gradual release of monosaccharide.

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

• A It is found in cell surface membranes.

• B It is synthesised from identical sub-units.

• C It is used as an energy source.

• D It may be a structural component.

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

• A Amylose has a branched structure and amylopectin is coiled to give a compact molecule for transport.

• B In the breakdown of amylose and amylopectin, many hydrolysis reactions release stored energy.

• C In the formation of amylose and amylopectin, many condensation reactions allow the release of stored energy.

• D The final amylose / amylopectin complex is insoluble and does not affect the osmotic properties of the cell.

Which linkages are found between the glucose units in cellulose?

• A α 1–4 only

• B α 1–4 and α 1–6

• C β 1–4 and α 1–6

• D β 1–4 only

Water is important to living organisms because it

• A acts as an excellent solvent for transport of dissolved glucose and urea.

• B becomes more dense in its solid form, ice, than its liquid state.

• C is used in condensation reactions to synthesise macromolecules.

• D requires a small increase in heat energy to raise its temperature.

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

• A 2 only

• B 3 only

• C 1 and 2

• D 1 and 3