DP Biology (last assessment 2024)
Question 18M.3.HL.TZ1.9b
| Date | May 2018 | Marks available | [Maximum mark: 3] | Reference code | 18M.3.HL.TZ1.9b |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Explain | Question number | b | Adapted from | N/A |
b.
[Maximum mark: 3]
18M.3.HL.TZ1.9b
The diagram shows an industrial anaerobic fermenter.
(b)
Explain factors that affect the rate of activity of microorganisms in fermenters.
[3]
Markscheme
a. changes of pH (possibly caused by changes of CO2) affect enzyme activity
b. ambient pressure / build-up of gases may affect reactions involving gases
c. increase of temperature could affect reaction rates /denature enzymes
d. decrease in nutrients/raw materials/change in substrate could decrease rate of product formation
e. increase in wastes could decrease rate of metabolism
f. particle size affects rate of fermentation associated with surface area (for substrate interactions)
g. mixing is necessary as sedimentation lowers surface area thus decreasing rate of reactions
