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CAIE A-Level Biology A2 12.1.4 Energy Values of Respiratory Substrates Questions

Use real CAIE questions and mark schemes to identify respiratory substrates, compare their energy values, and link lipid carbon–hydrogen bonds to reduced coenzymes, proton…

Syllabus
2028–2030
Course
Biology 9700
Level
A2

Exam points

  • Identify carbohydrate, lipid and protein respiratory substrates and compare their approximate energy values per gram.
  • Explain lipid’s higher energy value through more carbon–hydrogen bonds, more reduced coenzymes, a larger proton gradient and greater ATP yield.

CAIE A-Level Biology A2 12.1.4 Energy Values of Respiratory Substrates Questions question 1

[Maximum number: 2]

Lipids can be metabolised to provide ATP.
- The enzyme lipase hydrolyses lipids to glycerol and fatty acids.
- The hydrocarbon chain of the fatty acid breaks down into smaller, 2C compounds.
- Each 2 C compound reacts with coenzyme A to form acetyl coenzyme A.

Explain why lipids have a higher energy value than carbohydrates.

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