Oxford Revise AQA GCSE Combined Science Foundation | Chapter B5 answers

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Question Answers Extra information Mark AO / Specification reference
01.1

carbohydrase – carbohydrates

protease – proteins

lipase – lipids

1 mark for one or two correct

2 marks for all correct

 2

AO1

4.2.2.1
01.2 glucose   1

AO1

4.2.2.1
01.3 speeds up a reaction / does not get used up itself   1

AO1

4.2.2.1
02.1

catalysts

increase

specific

active

  

1

1

1

1

AO1

4.2.2.1
02.2 A   1

AO2

4.2.2.1
02.3

any one from:

  • pH
  • enzyme concentration
  • substrate concentration
   1

AO1

4.2.2.1
03.1 fatty acids and glycerol both needed for the mark 1

AO1

2.2.1
03.2 pancreas or small intestine   1

AO1

2.2.1
03.3 temperature   1

AO2

2.2.1
03.4 so they both were at the correct temperature / temperature being investigated   1

AO2

2.2.1
03.5 as temperature increased (until 35°C) rate of reaction increased / time taken to break down the lipid decreased   1

AO3

2.2.1
03.6

any two from:

  • no substrate/lipid was broken down
  • lipase/enzyme denatured
  • structure changed so it could no longer bind to lipid / lipid could not fit in active site
   2

AO3

AO2

2.2.1
04.1

between 10°C and 30°C, as temperature increases the rate of reaction increases

the enzyme does not catalyse the reaction at 60°C

  

1

1

AO3

4.2.2.1
04.2 37°C   1

AO3

MS4a

4.2.2.1
04.3

stop

denatured

active

  

1

1

1

AO1

4.2.2.1
05.1 proteins   1

AO1

4.2.2.1
05.2 to form proteins/enzymes/hormones/antibodies/structural tissue accept other sensible roles of amino acids 1

AO1

4.2.2.1
05.3 2.2   1

AO3

MS4a

4.2.2.1
05.4 stomach   1

AO2

4.2.2.1
05.5 stomach has low pH, as does the enzyme / optimum pH for enzyme in acidic conditions/low pH   1

AO1

4.2.2.1
06

Indicative content for method:

1 using the measuring cylinder, add fixed volume (e.g. 5 cm3) of starch solution to each test tube

2 using the pipette, alter pH of starch solutions by adding fixed volume (e.g. 1 cm3) of a different pH buffer solution to each tube

3 add one drop of iodine solution to each point on the spotting tile

4 using a pipette, add fixed volume (e.g. 1 cm3) carbohydrase solution to the first tube and stir/mix.

5 start stopwatch

6 using glass rod, remove a droplet of starchcarbohydrase mixture and add to the iodine solution

7 repeat this step every minute until iodine solution does not turn blue-black

8 record time value

9 repeat for all pH values being investigated

Safety precautions:

  • wear goggles
  • ensure glassware is kept in centre of workspace
  • use test-tube rack to hold test tubes

Control variables:

  • solutions at same temperature (check with thermometer)
  • use same volume of starch/carbohydrase/pH buffer in each tube
  • use same concentration of starch/carbohydrase/pH buffer in each tube

award up to 4 marks for description of a valid method to determine the time taken for amylase to digest starch, including correct identification and use of apparatus

award 1 mark for correctly identifying at least two control variables

award 1 mark for identifying at least one relevant safety precaution

 6

AO2

AO3

4.2.2.1
07.1 enzyme   1

AO1

4.2.2.1
07.2 orange to blue-black   1

AO1

4.2.2.1
07.3

points plotted to ±1 mm

smooth curve plotted through points

 award 2 marks if all points plotted correctly, award 1 mark for 3 or 4 plotted correctly

2

1

AO2

AO3

4.2.2.1
07.4 pH 7   1

AO3

4.2.2.1
08.1 fatty acids and glycerol   1

AO1

4.2.2.1
08.2 pancreas   1

AO1

4.2.2.1
08.3

lock

specific

active

protein

lipid

  

1

1

1

1

1

AO1

4.2.2.1
09.1 lipase   1

AO1

4.2.2.1
09.2 0.04   1

AO2

4.2.2.1
09.3 the enzyme/lipase is denatured (at this temperature) / the active site has changed shape   1

AO2

4.2.2.1
10.1 single-celled organisms have a large surface-area-to-volume ratio   1

AO1

4.1.3.1

4.2.2.2
10.2

any four from:

  • diaphragm contracts / flattens
  • intercostal muscles contract pulling ribcage up and out
  • volume of chest cavity increases
  • pressure inside chest cavity decreases
  • external / atmospheric air pressure greater (causing air to move into the lungs)
   4

AO1

4.2.2.2
10.3

spherical shape gives large surface area to maximise area for diffusion

thin walls allow a shorter diffusion distance

good blood supply maintains large diffusion gradient

  

1

1

1

AO1

4.1.3.1

4.2.2.2
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