Biochemistry and Respiration

Year 1 / ASYear 2 / A-Level All Boards (AQA, Edexcel, OCR, WJEC, CCEA) AQA

A-Level Biology revision: Biochemistry and Respiration. Learning objectives, key points, worked examples and practice questions across AQA, Edexcel, OCR, WJEC and CCEA.

Exam Board:

📌 Key Points

Key Fact: Glycolysis: glucose -> 2 pyruvate (cytoplasm); net 2 ATP, 2 NADH; Link: pyruvate -> acetyl CoA + CO₂ + NADH (mito matrix); Krebs: acetyl CoA + 3NAD⁺ + FAD + GDP -> 2CO₂ + 3NADH + FADH₂ + GTP; ETC: NADH/FADH₂ -> H⁺ gradient -> ATP synthase -> ATP

Key Fact: SLP: direct phosphate transfer (glycolysis, Krebs); OxPhos: H⁺ pumped across inner membrane, flow through ATP synthase

Key Fact: Theoretical: 10 NADH (2.5 each) + 2 FADH₂ (1.5 each) + 4 ATP = 32 ATP; Actual ~30-32

Key Fact: Anaerobic: animals: pyruvate + NADH -> lactate + NAD⁺ (lactate dehydrogenase); Yeast: pyruvate -> acetaldehyde + CO₂ -> ethanol + NAD⁺

Key Fact: Enzymes: globular proteins, active site, specific; Induced fit: substrate binding changes shape; Factors: temp, pH, [substrate], inhibitors (competitive/non-competitive)

Key Fact: Feedback inhibition: end product inhibits early enzyme; Allosteric: effector binds site != active site, changes conformation

🎯 Learning Objectives

Detail glycolysis, link reaction, Krebs cycle, oxidative phosphorylation
Explain substrate-level phosphorylation and oxidative phosphorylation (chemiosmosis)
Calculate ATP yield per glucose (theoretical vs actual)
Describe anaerobic respiration in animals (lactate) and yeast (ethanol)
Explain enzyme structure, mechanism (lock-and-key, induced fit), factors affecting activity
Understand metabolic pathways regulation: feedback inhibition, allosteric regulation

💡 Worked Example

Exam-Style Question

Question: Calculate total ATP from one glucose via aerobic respiration. Explain why yield is often less than theoretical

Model Answer:

Glycolysis: 2 ATP + 2 NADH (3-5 ATP); Link: 2 NADH (5 ATP); Krebs: 2 ATP + 6 NADH (15 ATP) + 2 FADH₂ (3 ATP) = 25-30 + 4 = 29-32 ATP. Less because: proton leak, shuttle costs (glycerol-3-P shuttle vs malate-aspartate), ATP for transport

❓ Practice Questions

Model answers are being added progressively - questions marked ✗ don't have one yet. Cross-check with your teacher or the official mark scheme.

Questions:

Where does each stage of respiration occur?✗ answer coming soon
Why does anaerobic respiration produce less ATP?✗ answer coming soon
Explain induced fit model✗ answer coming soon
How does cyanide affect respiration?✗ answer coming soon

🎬 Video Resources

Biochemistry and Respiration - Overview -- YouTube Search
Biochemistry and Respiration - Exam Questions -- YouTube Search

📄 Past Papers & Exam Resources

🔗 Further Reading & Resources

Physics & Maths Tutor - Biochemistry and Respiration -- Free notes, worksheets, and past paper questions by topic
Dr Frost Maths - Biochemistry and Respiration -- Free resources, slides, and interactive questions
BBC Bitesize - Biochemistry and Respiration -- BBC Bitesize revision resources

📚 Lesson Plan (50 minutes)

Starter (5 min): Recall prior knowledge of biochemistry and respiration with quick questions.
Teaching (15 min): Work through each of the learning objectives, explaining principles step by step.
Key points review (5 min): Revisit the key points together, confirming understanding.
Worked example (10 min): Model the example question: Calculate total ATP from one glucose via aerobic respiration. Explain why yield is often less than theoretical. Solution: Glycolysis: 2 ATP + 2 NADH (3-5 ATP); Link: 2 NADH (5 ATP); Krebs: 2 ATP + 6 NADH (15 ATP) + 2 FADH₂ (3 ATP) = 25-30 + 4 = 29-32 ATP. Less because: proton leak, shuttle costs (glycerol-3-P shuttle vs malate-aspartate), ATP for transport
Practice (10 min): Students attempt the practice questions independently; circulate and support.
Plenary (5 min): Review answers and address misconceptions.

🏠 Homework

Where does each stage of respiration occur?
Why does anaerobic respiration produce less ATP?
Explain induced fit model
How does cyanide affect respiration?

🧾 Assessment

Check practice answers against the model answer; use the built-in practice questions as formative assessment.

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