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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
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_60/2455675/57544_435999.gif)
- 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
![Condensation and hydrolysis reactions of triglyceride Condensation and hydrolysis reactions of triglyceride](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/2455675/343236_548812.png)
- 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
![Saturated fats have no double bonds. Monounsaturated fats have one double bond while polyunsaturated fats have more than one double bonds. Saturated fats have no double bonds. Monounsaturated fats have one double bond while polyunsaturated fats have more than one double bonds.](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/2455675/45766_474528.png)
Want to improve your IAL Edexcel Biology? Check out our study tips here
Time for a tummy rub~
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_60/2455675/720633_583265.gif)
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/