OCR AS Biology - Lipids

OCR AS Biology - Lipids

1. Biochemical Test

   • Ethanol Emulsion test
     • Step 1-Mix the sample with ethanol
       • This dissolves any lipid present
     • Step 2- Pour the liquid into water in another clean test tube
     • Step 3-If lipid is present a cloudy white emulsion will form near the top of the water
       • The lipid comes out of solution and becomes dispersed as tiny droplets in the water

2. Types of Lipids

   • Triglyceride
     • 1 Glycerol 3 Fatty Acids
       • Joined by Condensation to form 3 covalent bonds
     • Compact energy store insoluble in water so doesn't affect cell water potential
     • Ester links
     • Stored as fat
       • Thermal insulation
       • Protective purpose
   • Phospholipids
     • 1 Glycerol 2 Fatty Acids 1 Phosphate Group
       • Enter text here
     • Phosphate group may have carbohydrate parts attatched
       • Involved in Cell Signalling
     • Molecule is part hydrophobic and part hydrophilic
       • Ideal for cell membranes
   • Cholesterol
     • Small,thin molecule that fits into the lipid bilayer giving strength and stability
     • 4 Carbon based ring structures
     • Steroid hormones
       • Testosterone
       • Oestrogen

3. Key Components

   • Glycerol
     • Glycerol molecule always the same
     • 3 Carbon molecule with three OH groups
   • Fatty Acids
     • Molecule can differ significantly
     • Have an acid group at one end

4. Functions

   • Energy Source
   • Steroid Hormones
   • Insulation
   • Component of Cell Membranes
   • Protection
   • Energy Store

5. Key Features

   • Release large amounts of energy when respired
   • Contains Carbon,Hydrogen and small amounts of oxygen
   • Different types of fatty acids
     • C=C Unsatured
       • Common in plants
       • Cause fatty acid chains to push apart from other chains
       • More C=C chains = oils
       • More fluid
     • C-C Satured
       • Common in animals
       • Called fats
       • Less fluid
       • Solid at room temperature
   • Insoluble in water
   • Less dense than water

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