Movement and Plant Responses
Skeletal muscle contraction, neuromuscular control and how plants coordinate growth and physiological responses to environmental stimuli.
How to study A-level Biology
Move between scales deliberately: identify the biological process, trace matter or information, use quantitative evidence, then evaluate the method and conclusion.
Core concepts
Concept 1
Skeletal muscle force arises from calcium-regulated actin-myosin cross-bridge cycling powered by ATP.
Exam cue: Trace excitation from membrane depolarisation to calcium release and cross-bridge cycling.
Concept 2
Antagonistic muscles and the skeleton convert contraction into controlled movement.
Exam cue: Explain a joint movement by naming the contracting and relaxing members of an antagonistic pair.
Concept 3
Plants detect environmental cues and coordinate differential growth or physiological change using signalling molecules and altered gene activity.
Exam cue: Describe a plant response through perception, signal redistribution and differential cell response.
Risk pitfalls and guardrails
Saying ATP directly bends the myosin head only once per contraction.
Guardrail: Do not replace a mechanism with a vague purpose statement, or infer causation from an association without experimental support.
Assuming muscles push bones as well as pull them.
Guardrail: Do not replace a mechanism with a vague purpose statement, or infer causation from an association without experimental support.
Describing plant tropisms as movement toward a stimulus without explaining differential growth.
Guardrail: Do not replace a mechanism with a vague purpose statement, or infer causation from an association without experimental support.
Memory anchors
Sliding Filament
Thin actin filaments slide past thick myosin filaments, shortening the sarcomere.
Calcium
Calcium exposes actin binding sites by changing regulatory protein position.
Cross-bridge Cycle
Myosin binds actin, pivots, detaches using ATP and resets after ATP hydrolysis.
Antagonistic Pair
One muscle contracts while its antagonist relaxes to move a joint.
Tropism
A tropism is a directional growth response to an environmental stimulus.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
What shortens during skeletal-muscle contraction according to the sliding-filament model?
What exposes myosin-binding sites on actin?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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