| Date | May 2021 | Marks available | 1 | Reference code | 21M.1.HL.TZ1.40 |
| Level | Higher level | Paper | Paper 1 | Time zone | Time zone 1 |
| Command term | Question number | 40 | Adapted from | N/A |
Question
Expansin is a plant protein that loosens connections between cellulose fibres in plant cell walls, allowing growth. In what location would expression of the expansin gene be expected to be increased?
A. On the shaded side of a shoot being exposed to light
B. On the light side of a shoot being exposed to light
C. On the shaded side of a leaf that is transpiring rapidly
D. On the light side of a leaf that is transpiring rapidly
Markscheme
A
Examiners report
Candidates were not expected to be familiar with the role of expansin in the growth of plant cell walls but they were given the information they needed to deduce the answer to this question, as long as their understanding of phototropism was strong enough.
Syllabus sections
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21M.2.HL.TZ2.3a:
On the diagram, label the testa and the radicle.
- 17M.2.HL.TZ2.1b: Identify the relationship between the concentration of auxin and the age of the different...
- 18N.2.HL.TZ0.8b: Describe the roles of the shoot apex in the growth of plants.
- 17M.3.HL.TZ2.1a: In order to form galls, the insects choose a location where cell division occurs at a high...
- 18N.2.SL.TZ0.3b: In some areas there are gaps in the boreal forest where trees fail to grow and peat tends to...
- 18N.2.HL.TZ0.4b: In some areas there are gaps in the boreal forest where trees fail to grow and peat tends to...
- 17M.1.SL.TZ1.1: Which structure found in eukaryotes has a single membrane? A. Nucleus B. Lysosome C....
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18M.1.HL.TZ2.30:
The image shows seedlings that have been exposed to unidirectional light.
[Source: The Micro Gardener (https://themicrogardener.com/prevent-fix-leggy-seedlings/)]
Which statement explains the growth towards the light source?
A. Light causes auxin to inhibit cell division in the shoot meristem.
B. Light causes auxin to promote cell division in the shoot meristem.
C. Auxin is concentrated in the side of the shoot with light and inhibits cell elongation.
D. Auxin is concentrated in the side of the shoot without light and promotes cell elongation.
- 17M.2.HL.TZ2.1e: Based on all the data presented and your knowledge of auxin, discuss the pattern of auxin...
- 17M.2.HL.TZ2.1d.i: Compare and contrast the changes in auxin concentration in the stem base over time for the...
- 17M.2.HL.TZ2.1c: Analyse the effect of NPA on the formation of roots.
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22M.1.HL.TZ2.33:
The picture shows lentils sprouts growing towards a light source from the left.
[Source: Russell Neches, Lentil sprouts reaching for the sun [image online] Available at https://www.flickr.com/photos/rneches/2081938105/ This file is licensed under
the Creative Commons Attribution 2.0 Generic (CC BY 2.0)
https://creativecommons.org/licenses/by/2.0/.]How has this response been brought about?
A. A higher concentration of auxins on the light side caused faster photosynthesis.
B. A higher concentration of auxins on the shaded side caused faster meiosis.
C. A higher concentration of auxins on the shaded side caused faster cell elongation.
D. A higher concentration of chloroplasts on the light side allowed for more photosynthesis.
- 20N.1.HL.TZ0.33: How does auxin exert its effect on plant cells? A. Acts directly on the cell wall, causing...
- 17M.2.HL.TZ2.1d.ii: Deduce the effect of NPA on auxin transport between L6 and the stem base.
- 22M.1.HL.TZ1.34: What is an aspect of indeterminate growth in plants? A. The shoot apex retains...
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21M.2.HL.TZ1.6b:
Outline how the hormone auxin controls phototropism in plant shoots.
- 17M.2.HL.TZ2.1f.iii: The scientists concluded that auxin activates the transcription of the GH3 gene. Using the...
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16N.1.HL.TZ0.34:
What is/are the effect(s) of auxin in plants?
I. Increasing the rate of cell elongation in stems
II. Changing the pattern of gene expression in shoot cells
III. Detecting the direction of lightA. I only
B. I and II only
C. II and III only
D. I, II and III -
19M.1.HL.TZ2.39:
The photomicrograph shows a section through the top of a plant shoot.
[Source: Charles Good: The Ohio State University at Lima]
What are the structures labelled X and Y?
- 17M.2.HL.TZ2.1a: Calculate the difference in the concentration of auxin found in L1 and L6. . . . . . . . . ....
- 19N.2.HL.TZ0.8b: Outline the growth of plant shoot apex.
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17M.2.HL.TZ2.1f.ii:
Compare the pattern of GH3 transcription with the pattern of auxin concentration in the stem base control cuttings. You may use the table provided to help you to record the patterns before you compare them. (Please note: a simple
comparison in the table will not gain marks)
- 21M.1.HL.TZ2.34: How does auxin contribute to phototropism? A. It increases production of light-sensitive...
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21N.2.HL.TZ0.5c:
Outline the extension of the stem in plants.
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21N.1.HL.TZ1.33:
The diagram shows a plant shoot and the direction of the light which the shoot received.
[Source: USDA-NRCS PLANTS Database. Available at: https://commons.wikimedia.org/wiki/File:Alnus_seedling_drawing.png
[Accessed 30 November 2021].]What are the direction of movement and the effect of auxin in the tip of a plant shoot when receiving light from one side?
