Explain how the structure of a triglyceride makes it well suited to its function as an energy storage molecule in animals.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Triglycerides are non‑polar, hydrophobic molecules, so they can be stored in the body without water – an anhydrous form of energy storage.
Each triglyceride contains three fatty‑acid chains ester‑bonded to one glycerol backbone. The long chains are rich in C–H bonds, making the molecule highly reduced and capable of releasing more energy per gram than carbohydrates when oxidised.
The compact, dense arrangement of the three fatty‑acid chains allows a large amount of energy to be stored in a small volume or mass.
In animals triglycerides are stored under the skin and around organs, providing insulation and physical protection in addition to their energy‑storage role.
Each triglyceride contains three fatty‑acid chains ester‑bonded to one glycerol backbone. The long chains are rich in C–H bonds, making the molecule highly reduced and capable of releasing more energy per gram than carbohydrates when oxidised.
The compact, dense arrangement of the three fatty‑acid chains allows a large amount of energy to be stored in a small volume or mass.
In animals triglycerides are stored under the skin and around organs, providing insulation and physical protection in addition to their energy‑storage role.
Examiner tips
- Use the word "hydrophobic" to show understanding of non‑polar nature.
- Mention the ester bonds and glycerol backbone to justify the compact structure.
- Highlight the high C–H bond content to explain energy yield.
- Include the insulation/protection point to cover all scheme points.
Common mistakes
- Confusing triglycerides with phospholipids or misidentifying them as polar.
- Failing to mention the ester bonds or glycerol backbone.
- Omitting the insulation/protection aspect of storage.
Mark scheme (4 marks)
- Triglycerides are non-polar / hydrophobic molecules, so they are stored without water associated with them (anhydrous storage).
- Triglycerides contain a high proportion of C–H bonds / are highly reduced molecules, releasing more energy per gram than carbohydrates when oxidised.
- Three fatty acid chains are ester-bonded to one glycerol molecule, providing a compact / dense structure that stores large amounts of energy in a small volume / mass.
- Triglycerides stored under the skin / around organs also provide insulation / protection, adding to their functional value in animals.
Key terms in this question
Related
- All IB DP Biology Standard Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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