IB Biology HL 3.1.21 Auxin promotes cell growth Question Bank
Practise IB Biology HL 3.1.21 by applying auxin promotes cell growth concepts to exam-style questions.
- Syllabus
- First assessment 2025
- Course
- Biology HL
- Level
- HL
Exam points
- identify the relevant biological structure, process or evidence
- apply the correct biological mechanism to the question
- evaluate the result using data, adaptation or ecological reasoning
C3.1.21 (HL)—Auxin promotes cell growth question 1
[Maximum number: 2]
Plants have cell walls composed of cellulose.
When a plant cell grows, the cell wall must expand. Explain the role of auxin in cell wall expansion.
a. auxin causes (specific) genes to be transcribed/expressed;
b. stimulates proton pumps/causes movement of hydrogen ions into cell wall/through plasma membrane;
c. hydrogen ions/low pH/acidity loosens connections between cellulose (microfibrils/fibers)
OR
hydrogen ions/acidity activates expansin / expansin breaks/reforms connections between cellulose;
d. loosened cellulose can move apart/separate so wall becomes weaker/can expand;
2
Marking guidance:
max
Clarity of communication: [1]
The candidate's answers are clear enough to be understood without re-reading. The candidate has answered the question succinctly with little or no repetition or irrelevant material.
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