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1.5(i) Know how a triglyceride is synthesised by the formation of ester bonds during condensation reactions between glycerol and three fatty acids
1.5(ii) Know the differences between saturated and unsaturated lipids
- Lipids form part of cell membranes and are also used as energy store
- Generally insoluble in water but soluble in organic solvents (e.g. ethanol)
👇 One important type of lipid to remember for IAL Edexcel Biology 👇
Triglyceride
- Composed of 3 fatty acids and 1 glycerol joined via ester bonds
- Each ester bond is formed in a condensation reaction (catalyzed by an enzyme) in which a water molecule is released/ removed
- The fatty acids can differ in the following ways:
- Length of hydrocarbon chain (~8-20 carbons)
- Presence or absence of double bond(s)
- Combination of fatty acids (3 the same?)
Saturated vs unsaturated lipid
IAL Edexcel Biology exam tip, saturation refers to the number of hydrogen atoms in the molecule
- Saturated lipid
- No double bond between carbon atoms and maximum number of hydrogen
- Straight chain molecule --> stronger intermolecular force --> solid at room temperature
- Unsaturated lipid
- Has double bond(s) which means that fewer hydrogens can bind (less than maximum number of hydrogens)
- Has one or more kink in the chain --> weaker intermolecular force --> liquid in room temperature
Want to improve your IAL Edexcel Biology? Check out our study tips here
Time for a tummy rub~
References:
1. Edexcel AS Biology Revision Guide
2. https://alevelbiology.co.uk/notes/lipids-structure-functions/
3. https://medmunch.com/saturated-fats-what-you-need-to-know/