amazon.co.ukB3: Respiration, Photosynthesis and Bioenergetics
Glycolysis, Krebs cycle, oxidative phosphorylation, light-dependent and light-independent photosynthetic reactions.
📋 Key Definitions and Core Concepts
Chemiosmosis: ATP synthesis driven by proton electrochemical gradient across inner mitochondrial/thylakoid membrane through ATP synthase.
Photolysis: Light-dependent splitting of water in PSII: 2H₂O → 4H⁺ + 4e⁻ + O₂.
🔍 Key Principles & Specification Requirements
- Glycolysis: glucose → 2 pyruvate, net 2 ATP, 2 NADH (cytoplasm).
- Krebs cycle: acetyl-CoA oxidized producing 2 CO₂, 3 NADH, 1 FADH₂, 1 ATP per turn (mitochondrial matrix).
- Calvin cycle (stroma): RuBisCO fixes CO₂ to RuBP (5C) → 2 GP (3C) → reduced to 2 TP (3C) using ATP and NADPH.
💡 Worked Example Question
Exam-Style Question
Question:
Explain why oxygen is essential for aerobic ATP production.
Model Solution & Mark Scheme:
Oxygen acts as the terminal electron acceptor at complex IV of the electron transport chain. It combines with electrons and protons to form H₂O (½O₂ + 2H⁺ + 2e⁻ → H₂O), maintaining electron flow and proton gradient across the inner mitochondrial membrane.
❓ Practice Questions & Mark Schemes
Q1: What happens to the Calvin cycle in prolonged darkness?
Show Model Answer
Answer: Without light-dependent ATP and NADPH, GP cannot be reduced to TP. GP accumulates while RuBP and TP levels drop, halting glucose synthesis.
Q2: Calculate the respiratory quotient (RQ) for tripalmitin C₅₁H₉₈O₆ + 145/2 O₂ → 51 CO₂ + 49 H₂O.
Show Model Answer
Answer: RQ = CO₂ produced / O₂ consumed = 51 / 72.5 = 0.70.
🎬 Video Resources
- Respiration, Photosynthesis and Bioenergetics - Overview -- YouTube Search
- Respiration, Photosynthesis and Bioenergetics - Exam Questions -- YouTube Search
📄 Past Papers & Exam Resources
- AQA A-Level - Past Papers -- AQA
- Edexcel A-Level - Past Papers -- Edexcel
- OCR A-Level - Past Papers -- OCR
🔗 Further Reading & Resources
- Physics & Maths Tutor -- Free notes, worksheets, and past paper questions by topic
- Dr Frost Maths -- Free resources, slides, and interactive questions
- BBC Bitesize -- BBC Bitesize revision resources