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 👇

• 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 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~

Written by Vivian | GCE Biology Specialist @ TUTTEE

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/