May June 2015 89700/33

May June 2015 89700/33 :   HAzCard :

Candidates must be provided with a microscope with:

• Eyepiece lens, ×10 (equal to 16 mm or 23")

• Low-power objective lens, ×10 (equal to 16 mm or 23ʺ)

• High-power objective lens, ×40 (equal to 4 mm or 16ʺ)

• Eyepiece graticule fitted within the eyepiece and visible in focus at the same time as the specimen.

• For Both Question 

  • • • mm ruler

Question 1 :

• 
  

  • • • S1 10% sodium chloride 

      • S2 15% sucrose solution with 1g of glucose

      • S3 0.5% Starch solution

      • W Distilled water

• Reagents :

• • • Starch                                Iodine

    • Reducing sugars             Benedict

    • Non-reducing sugar     HCl 1.0-2.0M  Sodium Hydrogen carbonate (Solid, Solution 2.0M Blue litmus paper ?) Sodium hydroxide (Same M as HCL)

• Onion tissue : ONE pieces of onion tissue should be pre-soaked the day before the examination in each of S1, S2, S3 and W

Preparation of solutions and reagents:

Solutions and onion tissue must be prepared the day before and should be kept in covered containers in a refrigerator. However, they should be supplied to candidates at room temperature for the examination.

(i) S1, 10% sodium chloride solution to cover one piece of onion, in a beaker or container,

labelled S1.

This is prepared by dissolving 10 g of sodium chloride in 80 cm3 of distilled water and making

up to 100 cm3 with distilled water.

(ii) S2, 15% sucrose and glucose solution to cover one piece of onion, in a beaker or container

labelled S2.

This is prepared by dissolving 15 g of sucrose in 80 cm3 of distilled water and making up to

100 cm3 with distilled water. Stir well to dissolve the sucrose then sprinkle 1 g of glucose into

the 15% sucrose solution and stir well to dissolve the glucose.

You will need to prepare the following stock solution which will then be used to make 

S3: 1% starch solution

This is prepared by putting 1 g of starch (soluble) into 25 cm3 of warm distilled water in a

beaker or container and mixing to a paste. Make up to 100 cm3 with boiling distilled water, mix

well and then allow to cool.

(iii) S3, 0.5% starch solution to cover one piece of onion, in a beaker or container, labelled S3.

This is prepared by taking 50 cm3 of the 1% stock solution and making it up to 100 cm3 with

distilled water.

(iv) W, distilled water to cover one piece of onion in a beaker or container, labelled W.

(v) Reagents which candidates would normally use to test for the following carbohydrates:

• starch

• reducing sugar

• non-reducing sugar – the acid provided must be labelled ‘acid harmful’ and the alkali

provided must be labelled ‘alkali harmful’.

The containers should be labelled with the contents and the relevant hazard warnings. The biological molecule being tested should not be on the label, for example the iodine solution for starch test should have only the word ‘iodine’.

The hazard warning must be included on the label, either as the word e.g. “harmful” or as the pictogram/symbol.

The volumes supplied should be enough to carry out a minimum of 6 tests for each molecule.

The containers should be supplied with the means to add reagents into the test-tubes.

These reagents should be fresh for each candidate.

Apparatus for each candidate should be clean.

Syringe needles are not required and must not be given to candidates. Apparatus for each candidate Quantity ✓

• 2 cm3, 3 cm3 or 5 cm3 syringe with the means to wash it out  =2

• Pipette, plastic or glass with teat  =1

• Beaker or container (capacity at least 400 cm3), containing approximately 300 cm3 of tap water for pouring into test-tubes, labelled For washing = 1 (And one large at the back)

• Container (capacity at least 400 cm3), labelled For waste = 1 (and one large one at the back)

• Paper towels = 8

• Test-tube, suitable for heating, to hold a volume more than 15 cm3 and less than 20 cm3 = 3

• Test-tube rack or container to hold three test-tubes =1

• Test-tube holder to handle hot test-tubes  = 1

• Water-bath equipment for each candidate :

  • Bunsen burner, tripod, gauze, bench mat, at least a 250 cm3 clear beaker with water suitable for a water-bath (at a starting temperature between 45°C and 50°C),

• matches and a thermometer, –10°C to 110°C = 1

• Forceps (blunt) = 1

• Glass rod = 1

• Scalpel or sharp blade = 1

• Seeker or mounted needle 1

• Spotting tile or white tile 1

• Stop-clock or timer showing seconds = 1

• Glass marker pen = 1

• Safety goggles/glasses = 1

• Microscope slides and coverslips =  4

• Microscope as described on page = 2

For each candidate:

• the microscope must be set up on low power

• no slides must be on the stage of the microscope.