Control and coordination in plants
Cambridge A-Level Biology (9700) · Unit 15: Control and coordination · 7 flashcards
Control and coordination in plants is topic 15.2 in the Cambridge A-Level Biology (9700) syllabus , positioned in Unit 15 — Control and coordination , alongside Control and coordination in mammals. In one line: Expansins are enzymes that loosen the bonds between cellulose microfibrils in the plant cell wall. This allows the cell wall to become more flexible and stretchable, facilitating cell expansion.
Marked as A2 Level: examined at A Level in Paper 4 (A Level Structured Questions) and Paper 5 (Planning, Analysis and Evaluation). It is not tested on the AS-only papers (Papers 1, 2 and 3).
The deck below contains 7 flashcards — 2 definitions and 5 key concepts — covering the precise wording mark schemes reward. Use the 2 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
The function of 'expansins' during cell elongation
Expansins are enzymes that loosen the bonds between cellulose microfibrils in the plant cell wall. This allows the cell wall to become more flexible and stretchable, facilitating cell expansion.
What the Cambridge 9700 syllabus says
2025-2027 syllabus, in our words · A2 LevelWhat the syllabus expects you to be able to do in this topic, in plain English. For the exact wording, see the official syllabus (PDF).
- Describe how the Venus fly trap responds rapidly when the hairs on its modified leaf lobes are stimulated, and explain how the trap is made to close.
- Explain how auxin brings about elongation growth: it stimulates proton pumping, which acidifies cell walls.
- Describe what gibberellin does during barley germination (see 16.3.4).
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9700 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Describe the mechanism by which the Venus flytrap rapidly closes upon stimulation.
When the trigger hairs are bent twice within about 20 seconds (two hairs, or one hair twice), action potentials spread across the lobes. Ions move and water rapidly enters cells in the outer layers of the hinge region by osmosis, changing their turgor. The lobes flip from convex to concave and snap shut, trapping the insect.
Explain how auxin promotes cell elongation in plant shoots.
Auxin stimulates proton (H+) pumps in the plasma membrane, acidifying the cell wall. This activates expansins, enzymes that loosen cellulose microfibrils, allowing the cell to expand due to turgor pressure.
What is the role of gibberellin in barley seed germination?
Gibberellin from the embryo stimulates the aleurone layer to make amylase. Amylase hydrolyses starch stored in the endosperm to maltose, which is then broken down to glucose, giving the growing embryo a respiratory substrate for energy.
What is the function of 'expansins' during cell elongation?
Expansins are enzymes that loosen the bonds between cellulose microfibrils in the plant cell wall. This allows the cell wall to become more flexible and stretchable, facilitating cell expansion.
Describe the sequence of events that lead to the closure of the Venus flytrap leaf lobes when a fly lands on it.
Fly touches trigger hairs twice within about 20 s → action potentials spread across the lobes → rapid water movement by osmosis changes turgor of cells in the hinge region → lobes flip from convex to concave → trap snaps shut.
Explain the relationship between acidification of the cell wall and cell elongation.
Acidification of the cell wall by proton pumps activates expansins. Expansins loosen cellulose microfibrils. This makes the cell wall more flexible, allowing it to expand under turgor pressure, resulting in cell elongation.
What cells are involved in the gibberellin-mediated breakdown of starch in a barley seed?
Gibberellin produced by the embryo stimulates the aleurone layer to synthesize and secrete amylase. Amylase then hydrolyzes starch in the endosperm.
Review the material
Read full revision notes on Control and coordination in plants — definitions, equations, common mistakes, and exam tips.
Read NotesMore topics in Unit 15 — Control and coordination
Control and coordination in plants sits alongside these A-Level Biology decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Key terms covered in this Control and coordination in plants deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
How to study this Control and coordination in plants deck
Start in Study Mode, attempt each card before flipping, then rate Hard, Okay or Easy. Cards you rate Hard come back within a day; cards you rate Easy push out to weeks. Your progress is saved in your browser, so come back daily for 5–10 minute reviews until every card reads Mastered.
Study Mode
Rate each card Hard, Okay, or Easy after flipping.