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Edexcel A-Level Biology AS 4.4 Cellulose Microfibrils and Secondary Thickening Questions

Connect parallel or layered microfibrils to hydrogen bonding, add the effect of lignified secondary walls and use strength or waterproofing evidence to support comparisons.

Syllabus
First assessment 2019
Course
Biology YBI11
Level
AS

Exam points

  • explain tensile strength through hydrogen bonds between aligned cellulose microfibrils
  • compare primary and secondarily thickened walls through thickness and lignin
  • explain how secondary thickening and lignin affect strength, rigidity and waterproofing

Edexcel A-Level Biology AS 4.4 Cellulose Microfibrils and Secondary Thickening Questions question 1

[Maximum number: 4]

Abaca plants are found in the Philippines.
The photograph shows a mat made from abaca plant fibres.

Figure for Question Edexcel A-Level Biology AS 4.4 Cellulose Microfibrils and Secondary Thickening Questions question 1 — Edexcel A-Level Biology AS

Plant fibres include xylem vessels.

Explain how the arrangement of cellulose molecules and secondary thickening in xylem vessels contributes to the physical properties of the cell wall.

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