| Date | May 2018 | Marks available | 3 | Reference code | 18M.3.HL.TZ1.9 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 9 | Adapted from | N/A |
Question
The diagram shows an industrial anaerobic fermenter.
State one fuel that can be produced in this fermenter.
Outline one variable that must be controlled in an industrial fermenter
Explain factors that affect the rate of activity of microorganisms in fermenters.
The diagram represents the cell walls of Gram-positive and Gram-negative bacteria.
Label the layers I, II and III.
Markscheme
methane / biogas
a. anaerobic conditions / prevent entry of oxygen
b. warm temperatures / temperature above 15°C
c. different communities of microorganisms / Eubacteria and methanogens
d. proper pH needs to be maintained
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
l. peptidoglycan
ll. outer membrane/layer of lipopolysaccharide and protein
lll. peptidoglycan
