8(a)(i)
- Linear line that increases with temperature and then decreases;
accept carefully hand-drawn line sloping up to the optimum. (1)
- Optimum temperature shown at about 40 °C;
optimum must be above 30 °C and below 45 °C. (1)
8(a)(ii)
One valid route:
- values at 30 °C and 40 °C chosen, e.g. 50 and 32.5, and 50 and 22.5;
(1)
- rates calculated per minute, e.g. (50−32.5)÷5 = 3.5 and (50−22.5)÷5 = 5.5;
(1)
- numbers substituted into equation: 5.5 ÷ 3.5 = 1.5714;
(1)
- correct answer to 2/3 significant figures with no units: 1.6 / 1.57. (1)
OR using 40 °C and 50 °C: rates 5.5 and 0.5, Q10 = 0.5 ÷ 5.5 = 0.091 / 0.0909. Ecf from reasonable values read from graph.
8(b)(i)
- Mass of monosaccharides calculated to be 1361.3 / correct ratios expressed with more than one decimal place;
(1)
- ratios shown correctly as whole numbers or with disaccharide and tetrasaccharide values rounded to one decimal place. Example ratio: monosaccharide 164, disaccharide 7, trisaccharide 1, tetrasaccharide 1;
accept disaccharide 6.9 and tetrasaccharide 1.1. (1)
8(b)(ii)
D.
A, B and C are incorrect because inositol and raffinose have the modal concentration. (1)
8(b)(iii)
Indicative content:
General decomposition:
- bacteria and fungi are decomposers;
- decomposers release enzymes for decomposition;
- digested molecules are absorbed into the decomposer;
- carbon dioxide is released.
Carbohydrate decomposition:
- carbohydrases are needed to break down carbohydrates;
- hydrolysis of glycosidic bonds;
- to form monosaccharides;
- monosaccharides taken up by diffusion;
- glucose used in respiration;
- carbon dioxide produced by respiration of glucose.
Specific details relating to carbohydrates in the table:
- one glycosidic bond is broken in disaccharides, two in trisaccharides, three in tetrasaccharides;
- using one/two/three water molecules;
- e.g. sucrose broken down into glucose and fructose;
- monosaccharides do not need breaking down.
Ignore references to starch and amylase.
Levels:
- Level 1: general description of decomposition;
1 mark for one point, 2 marks for three points.
- Level 2: details about decomposition of carbohydrates;
3 marks for two points, 4 marks for three points.
- Level 3: specific details relating to carbohydrates in the table plus mention of respiration releasing carbon dioxide;
5 marks for specific detail for either di-/tri-/tetrasaccharides, 6 marks for specific detail for two of the three types of saccharides.