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1.6.3Unit 1 — Cell Biology

Aerobic Respiration — SQA National 5 Biology Revision Notes & Topical Questions

5 min read 4 parts Lesson 25 of 28

📚 SQA National 5 Biology Hub / Topical Revision
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Curriculum Equation Key Balanced Cellular Respiration EquationFast Exam Solution
C₆H₁₂O₆ + 6O₂ ➔ 6CO₂ + 6H₂O + 36-38 ATP
Word Equation & Conditions: Glucose + Oxygen -> Carbon Dioxide + Water + Energy (36-38 ATP)
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Part 1 of 4The Reaction

1.6.3 Aerobic Respiration

Aerobic respiration is the main way most organisms release energy from glucose.

Word equation
  • Glucose + oxygen → carbon dioxide + water + energy (transferred to ATP).
Balanced equation
  • C₆H₁₂O₆(aq) + 6O₂(g) → 6CO₂(g) + 6H₂O(l), with energy released to make ATP.
Oxygen needed
  • Oxygen is required, which is why aerobic respiration depends on breathing and blood transport in animals.
Complete breakdown
  • Glucose is broken down completely to carbon dioxide and water, so a lot of energy is released.

Part 2 of 4Where and How

1
Glucose is first broken down in the cytoplasm by enzymes into smaller molecules.
2
These molecules enter the mitochondria, where oxygen is used to complete the breakdown.
3
Carbon dioxide and water are produced and the energy released is used to make ATP.
4
Carbon dioxide diffuses out of the cell and is carried away to be breathed out.

Part 3 of 4Adaptations

Adaptations
Many mitochondria
  • Muscle cells, sperm tails and liver cells have large numbers of mitochondria to meet their high energy demand.
Oxygen supply
  • The lungs and circulatory system deliver oxygen to cells and remove carbon dioxide.
Glucose supply
  • Glucose comes from digested food and is carried to cells in the blood.
Rate
  • During exercise the rate of aerobic respiration increases, so breathing and heart rate also increase.

Part 4 of 4Exam Checklist & Tips

1.6.3 – Key Points for the Exam

  • Aerobic respiration Release of energy from glucose using oxygen.
  • Glucose The sugar used as the main fuel for respiration, C₆H₁₂O₆.
  • Mitochondria Organelles where oxygen is used to complete the breakdown of glucose.
  • Carbon dioxide A waste product of respiration, formula CO₂.

Common Mistakes

  • Saying oxygen is the fuel; glucose is the fuel and oxygen is needed to release energy from it.
  • Confusing the equation for respiration with that for photosynthesis, which is the reverse.
  • Writing that energy is a product that is made; it is released and transferred to ATP.
  • Leaving out state symbols or balancing numbers in the symbol equation.

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