Edexcel IAL Biology Unit 5 — Respiration, Internal Environment, Coordination and Gene Technology
Unit 5 (WBI15/01) covers respiration and muscles, the heart and kidney, the nervous system, brain and plant coordination, and gene technology. 90 marks in 1 h 45, with a 20-mark question built on a pre-released scientific article. Examined in January, June and October.
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What the WBI15 paper actually tests
Seventeen papers, 664 question parts, 2020 to 2026. The nervous system is the largest topic by a distance — 24% of classified marks. Regulation of breathing and heart rate (14%), respiration (13%) and the kidney (12%) follow. Muscles and the sliding filament theory, homeostasis and gene technology sit in the 6–9% band. The eye, plant coordination and the human brain are examined far less often than students expect from the length of the specification.
Command words: "Explain" again leads, then "Describe" and "Calculate". High-difficulty parts are around a quarter of the paper, concentrated in the article question and in the extended-response items on the nervous system and kidney. Revise the nervous system until action potentials, synapses and drugs at synapses are automatic; then the control of heart and breathing rate; then respiration and the kidney.
Share of marks by topic
17 papers · 664 question parts · 1190 classified marks · 2020–2026
Least examined
Command words, most to least common
Multiple choice (151), Explain (151), Describe (115), Calculate (68), Suggest (53), Comment (26).
What this means for you
The Nervous System, Regulation of Breathing & Heart Rate and Respiration carry 50% of the marks. Revise them first, then work down the list. Every solved question below is written in the mark-scheme words the examiner ticks.
The pre-released article: how to use it
Pearson publishes the article a few weeks before each sitting. Read it three times. First pass: understand the story. Second pass: write the specification point next to every paragraph — the article is chosen because it touches Topics 7 and 8 in unfamiliar contexts. Third pass: predict the questions. Typical stems are "Explain why the scientists…", "Suggest how…", "Describe the role of…" and one calculation from the data. Practise writing answers in mark-scheme words, not in the article's words: the examiner rewards the biology, not a paraphrase.
Topic 7: Respiration, muscles and the internal environment
Respiration is examined step by step: glycolysis, the link reaction, Krebs, then oxidative phosphorylation and chemiosmosis. Learn where each stage happens and what each produces. Anaerobic respiration, lactate fate and RQ follow — CP 15 uses a redox indicator in yeast and CP 16 a respirometer.
Muscles come as structure and mechanism: fibre types, the sliding filament theory with actin, myosin, troponin, tropomyosin, calcium and ATP. The heart is myogenic — SAN, AVN, bundle of His, Purkyne fibres — and you must read an ECG and calculate cardiac output. Breathing and heart rate are controlled from the medulla; CP 17 uses spirometer traces.
Homeostasis is negative and positive feedback, thermoregulation via the hypothalamus, and the kidney in full: ultrafiltration, selective reabsorption, the loop of Henle as a countercurrent multiplier and ADH control of plasma concentration. Finish with transcription factors and the difference between peptide and steroid hormones.
Topic 8: Coordination, response and gene technology
The nervous system: neurone types, myelination and saltatory conduction, resting and action potentials, the synapse and acetylcholine. Drugs at synapses are examined by named example — nicotine, lidocaine, cobra venom, L-DOPA, MDMA. The eye is covered through the rod cell and rhodopsin. Plant coordination is phytochrome, IAA and gibberellin; CP 18 measures amylase production in germinating grains.
The brain is examined through structure and imaging — MRI, fMRI, PET, CT — and through Parkinson's and depression. Gene technology closes the unit: recombinant DNA with restriction endonucleases and ligase, GM drugs from plants, animals and microbes, microarrays, bioinformatics and the risks and benefits of GMOs.
How to revise Unit 5 in the right order
- Nervous system — a quarter of the paper.
- Control of heart and breathing rate; respiration; the kidney.
- The article: three passes, spec points in the margin, predicted questions answered in mark-scheme language.
- Core practicals 15–18 as methods.
- Muscles, homeostasis, gene technology, then the rest with the checklist.
Unit 5 specification checklist
Topics 7 and 8, condensed point by point. Tick as you master each — progress is saved on this device.
Topic 7 — Respiration, Muscles and the Internal Environment
- 7.1 Aerobic respiration overall: substrate split, CO₂ released, hydrogen reunited with oxygen; a stepped, enzyme-controlled process
- 7.2–7.4 Glycolysis (hexose phosphorylation, substrate-level ATP, reduced coenzyme, pyruvate, lactate); link reaction and Krebs cycle in mitochondria; oxidative phosphorylation, chemiosmosis and ATP synthase
- 7.5–7.6 Fate of lactate after anaerobic respiration; respiratory quotient (RQ)
- 7.7 CORE PRACTICAL 15 — respiration in yeast with a redox indicator
- 7.8 CORE PRACTICAL 16 — respirometer: rate of respiration and RQ of germinating seeds or small invertebrates
- 7.9–7.11 Muscles, tendons, skeleton and ligaments; antagonistic pairs; skeletal muscle fibre structure; fast vs slow twitch; sliding filament theory with actin, myosin, troponin, tropomyosin, Ca²⁺, ATP and ATPase
- 7.12–7.14 Myogenic cardiac muscle; SAN, AVN, bundle of His, Purkyne fibres; ECGs; cardiac output; control of heart and ventilation rate by the medulla; adrenaline and fight-or-flight
- 7.15 CORE PRACTICAL 17 — exercise and tidal volume, breathing rate, minute ventilation and O₂ consumption from spirometer traces
- 7.16–7.17 Negative and positive feedback; homeostasis in exercise; hypothalamus and thermoregulation
- 7.18–7.21 Kidney structure; urea from excess amino acids and ultrafiltration; selective reabsorption; loop of Henle as countercurrent multiplier; ADH, osmoreceptors and pituitary control of plasma concentration
- 7.22 Transcription factors switching genes on and off; peptide hormones (extracellular) vs steroid hormones (intracellular)
Topic 8 — Coordination, Response and Gene Technology
- 8.1–8.3 Sensory, relay and motor neurones; Schwann cells and myelination; effectors responding to stimuli; spinal reflex arc, grey and white matter
- 8.4–8.6 Action potentials and Na⁺/K⁺ permeability; saltatory conduction; synapses, neurotransmitters, acetylcholine; pupil dilation and constriction
- 8.7 Drugs and nerve transmission — nicotine, lidocaine, cobra venom α-toxin, L-DOPA in Parkinson's, MDMA
- 8.8–8.10 Rod cells: rhodopsin, opsin, retinal, Na⁺, cation channels and hyperpolarisation; habituation; central and peripheral nervous systems
- 8.11 Phytochrome, auxin (IAA) and gibberellins in plant responses, including effects on transcription
- 8.12 CORE PRACTICAL 18 — amylase production in germinating cereal grains
- 8.13–8.16 Nervous and hormonal coordination; cerebral hemispheres, hypothalamus, pituitary, cerebellum, medulla; MRI, fMRI, PET, CT; dopamine in Parkinson's and serotonin in depression
- 8.17–8.19 Drugs from GM plants, animals and microbes; recombinant DNA with restriction endonucleases and DNA ligase; inserting it into other cells
- 8.20–8.22 Microarrays and active genes; bioinformatics; risks and benefits of GMOs
Condensed from the Pearson Edexcel International Advanced Level in Biology specification, Issue 2 (2018 qualification, units WBI11–WBI16). Always check the full wording in the official specification.
Unit 5 — FAQ
What is the pre-released article in IAL Biology Unit 5?
Pearson releases a scientific article before each Unit 5 sitting. One 20-mark question on the paper is built on it, testing whether you can apply Topic 7 and 8 ideas to an unfamiliar context. Read it several times and annotate every paragraph with the spec point it connects to.
Which Unit 5 topics carry the most marks?
Across 2020–2026 papers the nervous system is about 24% of classified marks, followed by regulation of breathing and heart rate, respiration and the kidney at 12–14% each. The eye, plant coordination and the human brain are examined far less often.
Does Unit 5 include Unit 1 and 2 content?
Yes — synoptic questions can draw on Units 1 and 2, most often membranes, proteins and enzymes, and the heart and circulation from Unit 1.
How is Unit 5 marked toward the A*?
Unit 5 is 20% of the IAL. For an A* you need an A overall (480 UMS) and at least 90% of the UMS across Units 4, 5 and 6 combined (270 of 300).
About this page
About Edexcel IAL Biology Unit 5 (WBI15/01). Unit 5, Respiration, Internal Environment, Coordination and Gene Technology, is one of the three IA2 units of the Pearson Edexcel International Advanced Level in Biology (YBI11), examined in January, June and October. It is a 90-mark, 1 h 45 written paper worth 20% of the full IAL. The topic checklist on this page is a condensed study companion to the official specification (Issue 2); the marks analysis is Chem Bio's classification of every question part in 17 WBI15 papers from 2020 to 2026 (664 parts, 1190 marks) by topic, command word and difficulty. Written by Hosni Showike, Head of Science, 21 years teaching Edexcel IAL Biology.
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Every WBI15 question since 2020, solved for the marks
Point-by-point model answers in mark-scheme language, the notes written on this specification, and WhatsApp support from Mr Hosni until exam day.
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