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2.8.4Inquiry Process

Requirements for Movement — IB Biology HL Revision Notes & Topical Questions

5 min read 4 parts Lesson 89 of 160

📚 IB Biology HL Hub / Topical Revision
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Section 1 of 4Energy for Contraction

2.8.4 Requirements for Movement
ATP use
  • ATP is needed to detach myosin heads from actin, reset the heads and pump calcium ions back into the sarcoplasmic reticulum.
Stored ATP
  • Muscle holds only a few seconds' worth of ATP, so it must be regenerated continuously.
Creatine phosphate
  • This store transfers phosphate to ADP and rapidly restores ATP for the first seconds of intense activity.
Aerobic respiration
  • Mitochondria produce large amounts of ATP from glucose or fatty acids, using oxygen delivered by blood and stored by myoglobin.
Anaerobic respiration
  • When oxygen is limited, glycolysis produces a small amount of ATP and lactate accumulates, causing fatigue.
SourceSpeedDuration
Creatine phosphateVery fastA few seconds
AnaerobicFastShort bursts
AerobicSlowerLong periods

Section 2 of 4Supplies and Control

Supplies and Control
Blood supply
  • Capillaries bring glucose, fatty acids and oxygen and remove carbon dioxide and heat.
Myoglobin
  • This red pigment in muscle stores oxygen and releases it when oxygen is scarce.
Nerve signals
  • Motor neurons release acetylcholine at neuromuscular junctions to trigger contraction.
Calcium ions
  • Ions must be released and then pumped back to allow contraction and relaxation.

Section 3 of 4Mechanical Requirements

1
Muscles can only pull, so they work in antagonistic pairs: when one contracts the other relaxes.
2
Tendons connect muscles to bones, transmitting the pull without stretching much.
3
The skeleton provides a rigid lever for the muscles to act on.
4
Joints allow bones to move relative to each other in controlled directions.
5
After vigorous exercise, extra oxygen is taken in to remove lactate and restore ATP and creatine phosphate stores.

Section 4 of 4Exam Checklist & Tips

2.8.4 – Key Points for the Exam

  • Creatine phosphate A store of phosphate that can regenerate ATP rapidly.
  • Myoglobin An oxygen-storing protein in muscle cells.
  • Lactate The product of anaerobic respiration in animal muscle.
  • Antagonistic pair Two muscles that produce opposite movements at a joint.

Common Mistakes

  • Saying that muscles produce ATP from nothing; they must regenerate it from respiration.
  • Stating that lactate is the cause of muscle soreness days later.
  • Claiming that muscles can push as well as pull.
  • Confusing myoglobin with haemoglobin; myoglobin stays in muscle.

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