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1.6.1Unit 1 — Cell Biology

Respiration in Cells — SQA National 5 Biology Revision Notes & Topical Questions

5 min read 4 parts Lesson 23 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 4What Respiration Is

1.6.1 Respiration in Cells

Respiration is not breathing; it is a chemical process inside cells.

Chemical process
  • Respiration is a series of enzyme-controlled reactions that break down nutrient molecules, mainly glucose.
Releases energy
  • The energy released is used to make ATP, a molecule that stores and transfers energy for the cell.
All cells
  • Respiration takes place in every living cell, all the time.
Mitochondria
  • Most of the reactions of aerobic respiration take place in mitochondria.

Part 2 of 4ATP

1
Energy released from glucose is used to join a phosphate to ADP, making ATP.
2
ATP moves to the part of the cell where energy is needed.
3
When ATP is broken down to ADP and phosphate, it releases energy for cell activities.
4
ADP and phosphate are recycled and used again in respiration to make more ATP.

Part 3 of 4Uses of Energy

Uses of Energy
Muscle contraction
  • Muscle cells use ATP to contract and so allow movement of the body.
Protein synthesis
  • Joining amino acids into proteins needs energy supplied by ATP.
Cell division
  • Growth and replacement of cells require energy for the processes of mitosis.
Active transport
  • Moving substances across membranes against a gradient depends on ATP.
Nerve impulses and temperature
  • Generating nerve impulses and maintaining body temperature in mammals also need energy.

Part 4 of 4Exam Checklist & Tips

1.6.1 – Key Points for the Exam

  • Respiration Enzyme-controlled reactions that release energy from nutrients such as glucose.
  • ATP The molecule that transfers energy to cell processes.
  • ADP The molecule left when ATP releases energy, which can be recycled to make ATP.
  • Mitochondrion The organelle where most of aerobic respiration occurs.
  • Aerobic Happening with oxygen.

Common Mistakes

  • Confusing respiration with breathing or gas exchange.
  • Saying that energy is made in respiration; energy is released and transferred, not created.
  • Writing that only animals respire; plants and all other living things respire as well.
  • Thinking mitochondria are where photosynthesis occurs; that is chloroplasts.

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Cambridge 9700 AS Biology Core Formula

Magnification Triangle & Unit Conversion

Formula: M = I / A  ⇔  A = I / M  ⇔  I = M × A

Units: 1 mm = 1,000 μm = 1,000,000 nm.
Rule: Convert Image size (ruler mm) to μm by ×1,000 before dividing by Actual size.