| Date | November 2021 | Marks available | 1 | Reference code | 21N.1.HL.TZ1.29 |
| Level | Higher level | Paper | Paper 1 | Time zone | Time zone 1 |
| Command term | Question number | 29 | Adapted from | N/A |
Question
Some bacteria can synthesize the amino acid isoleucine from threonine, a process involving five enzymes (E1 to E5) and four intermediary products (P, Q, R and S). The production of isoleucine is controlled by end-product inhibition.
Which statement describes this end-product inhibition?
A. If isoleucine accumulates, it inhibits the production of P.
B. End-product inhibition causes a build-up of intermediary products.
C. Isoleucine inhibits E5, so no more isoleucine is produced.
D. Isoleucine affects the structure of threonine.
Markscheme
A
Examiners report
Syllabus sections
- 18N.1.HL.TZ0.28: The graph shows the effect of substrate concentration on the rate of an enzyme-catalysed...
- 18N.2.HL.TZ0.1c: State the highest concentration of cotinine in the urine, giving the units.
- 17M.1.HL.TZ1.31: The graph shows the rate of an enzymatic reaction versus the substrate concentration, in the...
- 17M.1.SL.TZ1.1: Which structure found in eukaryotes has a single membrane? A. Nucleus B. Lysosome C....
- 17M.2.HL.TZ2.2a: The sketch shows the relationship between the reaction rate and substrate concentration in...
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19N.1.HL.TZ0.29:
The grey line in each of the graphs below represents the rate of reaction catalysed by an uninhibited enzyme as substrate concentration is increased.
Which graph shows expected results if a competitive inhibitor was added to the reaction?
[Source: © International Baccalaureate Organization 2019]
- 16N.1.HL.TZ0.29: The graph shows an example of an enzyme-catalysed reaction. What does the curve labelled X...
- 22M.1.HL.TZ1.29: The graph shows the effect of increasing substrate concentration on the rate of an...
- 16N.2.HL.TZ0.3b: Outline the importance of enzymes to metabolic processes.
- 18N.1.HL.TZ0.31: Which is a reduction reaction? A. ATP changing to ADP B. Maltose changing to glucose C. ...
- 18N.2.HL.TZ0.1d.i: Deduce, with a reason, whether the concentrations of cotinine and NNAL-Gluc would be higher...
- 20N.1.HL.TZ0.29: Sulfanilamide inhibits an enzyme that catalyses a reaction involving PABA, an intermediate in...
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21M.2.HL.TZ1.8c:
Explain the factors that affect the rate of enzyme-controlled reactions in cells.
- 18N.2.HL.TZ0.1d.ii: Suggest one advantage of using the urine concentration of cotinine rather than NNAL-Gluc to...
- 19M.2.HL.TZ1.7a: Outline the roles of helicase and ligase in DNA replication.
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19M.1.HL.TZ1.29:
The first enzyme in the metabolic pathway that produces isoleucine is threonine deaminase. Which graph illustrates the relationship between threonine deaminase activity and threonine concentration?
[Source: © International Baccalaureate Organization 2019]
- 19M.2.HL.TZ1.5b: Outline the control of metabolism by end-product inhibition.
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21N.2.HL.TZ0.8c:
Distinguish between competitive and non-competitive enzyme inhibition.
- 18M.2.HL.TZ1.5d: The graph shows energy levels throughout an uncatalysed reaction. Draw a curve to show how...
- 18M.1.HL.TZ2.13: Metabolic pathways are dependent on enzyme-catalysed reactions. Which term corresponds with...
