| Date | May 2011 | Marks available | 3 | Reference code | 11M.3.HL.TZ2.7 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Analyse | Question number | 7 | Adapted from | N/A |
Question
Fungi of the genus Botryosphaeria have been found to produce certain oxidizing enzymes, laccases, that are effective in treating contaminated water and soils. Studies were undertaken to test the effects of veratryl alcohol concentrations and fermentation time in order to optimize the industrial production of laccases. Statistical analysis of the data was used to develop the graph below.
Identify the amount of laccases produced when the veratryl alcohol concentration is at its highest level and the fermentation time is at its shortest.
Identify the amount of laccases produced when the veratryl alcohol concentration is at its lowest level and the fermentation time is at its longest.
Analyse the overall effects of the veratryl alcohol concentration and fermentation time on the production of laccases.
Suggest two other conditions that might affect the production of laccases.
Markscheme
1.6 (units) cm–3 (accept answers in range of 1.5 units cm–3 and 1.7 units cm–3)
8.3 (units) cm–3 (accept answers in range of 8.2 units cm–3 and 8.4 units cm–3)
as fermentation time increases laccase production rises then falls; (accept converse)
as veratryl alcohol concentration increases laccase production rises then falls; (accept converse)
optimum fermentation time is 4.75/5.0/5.25 days; (accept converse)
most laccase overall with low veratryl alcohol concentration and long fermentation; (accept converse)
optimum veratryl alcohol concentration is 33/34/35 mmol dm–3;
fermentation time has greater effect than veratryl alcohol concentration;
temperature;
pH;
oxygen concentration;
carbon dioxide concentration;
build up of waste/toxic products of metabolism;
amount of contamination;
light;
supply of raw materials/nutrients/sugar;
concentration of fungi;
presence of other fungi/bacteria;
Examiners report
This proved to be very challenging, but it was balanced by relatively straightforward questions later in this option. The three-dimensional graph was not studied carefully enough by some candidates. Answers to (a)(i) and (ii) were sometimes therefore incorrect.
This proved to be very challenging, but it was balanced by relatively straightforward questions later in this option. The three-dimensional graph was not studied carefully enough by some candidates. Answers to (a)(i) and (ii) were sometimes therefore incorrect.
Part (b) was also answered poorly by many candidates. As they increase, both veratryl alcohol concentration and fermentation time cause an increase in the production of laccases, up to an optimum, beyond which there is a decrease. Few candidates described this clearly.
Part (c) was more successfully answered and in most cases two acceptable other conditions were given.
