Carbohydrate & Water Test ( /50)

CARBOHYDRATE & WATER TEST ( /50)

Name………………………..Tutor…….

1. (a)Identify the carbohydrate referred to in each of the following statements. [3]

(i) This substance is present in some animal tissues. It is a branched molecule and each branch is formed from about 10-20 glucose units.

…………………………………………………………………………………………..

(ii) This compound gives a blue colour with iodine solution. It is composed of long, unbranched chains of glucose units.

……….…………………………………………………………………………………..

(iii) This substance, found in plants, also reacts with iodine solution, but the colour produced is more purple than blue. The molecules are large and branched, being composed of glucose units joined by both 1-4 and 1-6 glycosidic bonds.

……………………………………………………………………………………………

(b) (i) Which substance is most usually found in phloem sieve tubes as a 'transport' carbohydrate?

………………………………………………………………………………………..[1]

(ii) Suggest two reasons why this carbohydrate is used and not others. [2]

…………………………………………………………………………………………….

2. (a) Fill in the missing words in the following passage.[8 x ½ = 4]

Honey contains several carbohydrates. If it is tested with ……………………solution,

the ……………….colour of the reagent changes to orange as a precipitate forms on boiling. This indicates that a carbohydrate contained in the honey is a...... ………...... Its chief function in the human body is as a source of ………………. but if it is not used immediately it is transported to the ………………… or to the ……………….. where it is converted into …………………….. and stored.

(b) (i) Briefly explain the cause of the orange precipitate referred to in the passage. [1]

…………………………………………………………………………………………

(ii) Suggest one storage carbohydrate found in plants which is similar in structure to the storage compound being considered in the passage. [1]

…………………………………………………………………………………………………….

(iii) Why can we digest some polysaccharides but not others? Give one example of a polysaccharide which we cannot digest. [3]

…………………………………………………………………………………………………..

3. If a molecule of glucose is C6H12O6 write an equation to show how two molecules of glucose are joined to form maltose. [3]

……………………………………………………………………………………………………..

What is the general name given to describe this type of reaction? [1]

…………………………………………………………………………………………………….

What isthe name given to the bond formed when monosaccharides are joined together?[1]

…………………………………………………………………………………………………….

State two ways by which the reverse of the reaction could be brought about.[2]

i ……………………………………………………………………………………..

ii …………………………………………………………………………………….

4. Place ticks () in the columns of reagents/techniques which would be used to test for the substances listed. [5]

Biuret reagent / Benedict’s solution / Dil. HCl / Iodine solution / Ethanol / Water / Dilute alkali / Heat
Cellulose
Reducing Sugar
Non-reducing sugar
Protein
Lipid

5. Scientists have concluded that there is little chance of life on Mars or any of the other planets in the solar system because they do not have any liquid water.

(a) Suggest a chemical test which could be used to show that water is lost from the surface of a leaf. Indicate any change of colour which you might expect. [1]

…………………………………………………………………………………………………………...

……………………………………………………………………………………………………………

(b) (i) Briefly state why water is described as a polar molecule.[1]

…………………………………………………………………………………………………………..

(ii) Water molecules are attracted to each other by weak electrical charges. What is the name given to these weak bonds? [1]

……………………………………………………………………………………………………

(c) The solvent properties of water are a result of its polar nature, and this enables life to exist on this planet. Give two other properties of water which are influenced by its polar nature. [2]

(i) ………………………………………………………………………………………………

(ii)………………………………………………………………………………………………

(d) Use a simple chemical or word equation to show a biological example of:[2]

(i) hydrolysis;

...... …...... ……………………………………………………………......

(ii) condensation.

...... …………………………………………………………………………………………......

(e) List 4 uses of water in living things. [4]

i. ………………………………. ii ……………………………………….

iii ……………………………….. iv ………………………………………..

(f) Name two properties of cellulose which make it suitable to be used in plant cell walls[2]

...... ………………………………………………………………………………………….

………………………………………………………………………………………………………….

6. The table below refers to the nature of a number of carbohydrates.

If the statement is correct for that carbohydrate place a tick () in the appropriate box and if the statement is incorrect place a cross (X). [6]

Statement / Carbohydrate
cellulose / fructose / glycogen / maltose / starch / sucrose
reducing sugar
polysaccharide
produces mono-saccharides on complete hydrolysis

7 (a) (i) The diagram shows two α glucose molecules. Indicate diagrammatically how these two molecules are linked to form the disaccharide maltose. [2]

(e) Name two other disaccharides .

(i) ...... …………... . . ………….. (ii)...... [2]