A Level Biology Lesson 8:

Lipids: The Properties of Triglycerides

Task 1. Check Where this Lesson fits into your Exam Specification!

Task 2. Watch the Revision Notes Lesson in Full.

00:00 Learning Outcomes

00:51 The Structure of a Triglyceride is related to its function

01:13 Lipids are not Polymers

02:00 Lipids are hydrophobic

02:46 Lipids are useful energy storage molecules

03:07 Lipids are waterproofing agents

03:30 Lipids are great insulators and protectors

04:30 Lipids play important roles as steroids

Task 3. 

Download, Print out & complete the accompanying Interactive Worksheet.


A-Level Biology "Lipids: The Properties of Triglycerides" Lesson 8. Summary.

 The structure of triglycerides is related to their functions. For example, the long hydrocarbon tail of the fatty acid part of “fats” is an important source of energy. In fact, fatty acids contain around twice as much energy per gram than do carbohydrates.


Remember! Lipids are NOT considered Polymers (because they are NOT composed of many repeating monomers).


Lipids are made up from: - Glycerol + Fatty acids.


Fats and oils are insoluble in water, and this hydrophobic nature of lipids allows them to “bundle” together forming fat droplets. It is also yet another reason fat is a great energy storage molecule, since they don’t affect the water potential of cells.


The hydrophobic properties of lipids make them useful waterproofing agents, e.g. bird feathers, leaves the waxy exoskeletons of many insects.


Fats have a low density which makes them useful for buoyancy, insulation and protection.


Lipids play important roles as steroids (e.g. Cholesterol).


Lipids are useful respiratory substrates. During Cellular Respiration, lipids are oxidised and the bonds of the hydrocarbon tail are hydrolysed – the products of which enter the ‘link reaction’ to produce ATP.

Check Your Spec!

★ AQA Specification Reference: - 3.1 Biological molecules: 3.1.3 Lipids. Triglycerides and phospholipids are two groups of lipid. The different properties of triglycerides. Students should be able to explain the different properties of triglycerides.


★ CIE Specification Reference: - 2 Biological molecules. 2.2 Carbohydrates and lipids. lipids have important roles in the provision and storage of energy, and for a variety of other functions must be able to relate the structure of triglycerides to their functions in living organisms.


★ Edexcel (Biology A – Salters-Nuffield) Specification Reference: - Topic 2: Genes and Health. 2.2 i) Know the structure and properties triglycerides.


★ Edexcel (Biology B) Specification Reference: - Topic 1: Biological Molecules. iii) Understand how the structure of lipids relates to their role in energy storage, waterproofing and insulation.


★ OCR (Biology A) Specification Reference: - Module 2: Foundations in biology - 2.1.2 Biological molecules. (j) how the properties of triglycerides relate to their functions in living organisms.


★ OCR (Biology B) Specification Reference: - Module 2: Cells, chemicals for life, transport and gas exchange. (j) how the structure of triglycerides is related to their functions. To include reference to fatty acids, glycerol, phosphate groups, ester bonds and hydrophobic/ hydrophilic properties.


★ WJEC Specification Reference: - Core Concepts 1. Chemical elements are joined together to form biological compounds (f) the structure, properties and functions of lipids as illustrated by triglycerides [and phospholipids].



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1Fractured DNA



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