| Date | November 2020 | Marks available | 2 | Reference code | 20N.3.sl.TZ0.8 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Calculate | Question number | 8 | Adapted from | N/A |
Question
Biomagnification factor, BMF, can be defined as the concentration of a chemical, , in a predator, relative to the concentration found in its prey.
BMF, where ( per body weight)
| [Franklin, J., 2015. How reliable are field-derived biomagnification factors and trophic magnification factors as indicators of bioaccumulation potential? Conclusions from a case study on per- and polyfluoroalkyl substances. Available at: https://setac.onlinelibrary.wiley.com/doi/full/10.1002/ieam.1642.] |
Calculate the BMF if a shark consumes mackerel in one year. Each mackerel weighs on average. The per body weight. Assume chemical remains in the shark’s body for two years.
Suggest, with a reason, if fat-soluble or water-soluble xenobiotics would have a larger BMF.
Markscheme
✔
✔
Award [2] for correct final answer.
M2 may also be correctly expressed to SF.
fat-soluble AND pass through lipid membranes/accumulate in cells/fatty tissues
OR
fat-soluble AND less easily excreted/metabolized ✔
Accept “water-soluble” only if an organometallic–protein interaction is mentioned.
Examiners report
Many candidates produced the correct answer for M1 but not as many fully scored. Students did not appear to understand the concept, and many missed the idea of 2 years in the calculation. Students should always clearly show their calculations so examiners can award marks throughout the question and potentially award ECF if possible. It is very difficult to do this when students do not show work clearly.
A well answered question although some did not give a reason.
Syllabus sections
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17M.3.sl.TZ1.13f:
Outline how lead ions could be removed from an individual suffering from lead poisoning.
- 19N.3.hl.TZ0.14b: Explain the biomagnification of the pesticide DDT.
- 18N.3.sl.TZ0.5c: Explain how a xenobiotic is biomagnified.
- 18N.3.sl.TZ0.6b.ii: Enzymes are widely used in washing detergents. Outline how they improve the efficiency of the...
- 19N.3.sl.TZ0.10b: Explain the biomagnification of the pesticide DDT.
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19M.3.sl.TZ2.6c(ii):
Oil spills can be treated with an enzyme mixture to speed up decomposition.
Outline one factor to be considered when assessing the greenness of an enzyme mixture.
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16N.3.sl.TZ0.9c:
Amylose is an unbranched polysaccharide composed of repeating units of glucose.
(i) Draw the structure of the repeating unit of amylose. Use section 34 of the data booklet.
(ii) Amylose is a major component of starch. Corn starch can be used to make replacements for plastics derived from oil, especially for packaging. Discuss one potential advantage and one disadvantage of this use of starch.
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18M.3.sl.TZ1.7c.iii:
Explain why sharks and swordfish sometimes contain high concentrations of mercury and polychlorinated biphenyls (PCBs).
- 19N.3.sl.TZ0.8c: State one use of enzymes in reducing environmental problems.
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19M.3.hl.TZ1.8d:
Explain how the inclusion of starch in plastics makes them biodegradable.
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19M.3.sl.TZ2.6c(i):
Suggest two reasons why oil decomposes faster at the surface of the ocean than at greater depth.
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17M.3.sl.TZ1.12c.i:
State one advantage of starch based polymers besides being biodegradable.
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19M.3.hl.TZ2.9d(ii):
Oil spills can be treated with an enzyme mixture to speed up decomposition.
Outline one factor to be considered when assessing the greenness of an enzyme mixture.
-
17M.3.sl.TZ2.10d:
Suggest one of the challenges scientists face when scaling up the synthesis of a new compound.
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17M.3.sl.TZ2.10c:
Starch is a constituent of many plastics. Suggest one reason for including starch in plastics.
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17N.3.sl.TZ0.9c:
Explain how the inclusion of carbohydrates in plastics makes them biodegradable.
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17M.3.sl.TZ1.13e:
Pollution from heavy metal ions has become a health concern.
Outline how the presence of heavy metal ions decreases the action of enzymes.
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18M.3.sl.TZ2.8:
Green Chemistry reduces the production of hazardous materials and chemical waste.
Outline two specific examples or technological processes of how Green Chemistry has accomplished this environmental impact.
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19M.3.hl.TZ2.9d(i):
Suggest two reasons why oil decomposes faster at the surface of the ocean than at greater depth.
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18M.3.sl.TZ1.7c.iv:
Plastics are another source of marine pollution. Outline one way in which plastics can be made more biodegradable.
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19M.3.sl.TZ1.7d:
Explain how the inclusion of starch in plastics makes them biodegradable.
- 20N.3.sl.TZ0.8b: Suggest, with a reason, if fat-soluble or water-soluble xenobiotics would have a larger BMF.
