Question 17N.3.SL.TZ0.10
| Date | November 2017 | Marks available | [Maximum mark: 5] | Reference code | 17N.3.SL.TZ0.10 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Explain, Identify, State, Suggest | Question number | 10 | Adapted from | N/A |
Researchers in Korea set up an experiment to measure how accumulation of biofilm changes in water pipes under different conditions.
The graph shows the accumulation of biofilm in steel pipes when the water was untreated, treated with chlorine and filtered through a membrane.
[Source: adapted from Yoonjin Lee, (2013), Journal of Environmental Research Public Health 2013, 10 (9), pages 4143 – 4160]
State the effect chlorination has on the accumulation of biofilm in the pipe.
[1]
reduces «the accumulation of biofilm»
Suggest why membrane filtration may be more suitable than chlorination in purifying the water.
[1]
a. does not affect taste of water/no chemicals added
b. lower biofilm accumulation over time
[Max 1 Mark]
Identify which two pipes would be required to study the effect of heat on biofilm accumulation.
[1]
A and B
Both required
Explain how quorum sensing benefits the bacteria within the steel pipes.
[2]
a. quorum sensing is a means of communication between bacteria
b. allows the bacteria to synchronize their activities/work together
c. they can change according to the environment/conditions in the pipe
d. control cell density/gene expression
[Max 2 Marks]