B1.1.7 Triglycerides and Phospholipids
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Which 3 elements do lipids contain?
Carbon Hydrogen Oxygen
Which part of a phospholipid is hydrophilic?
The phosphate ‘head’
Identify the molecule
Polyunsaturated fatty acid
What does hydrophobic mean?
water hating
How does the structure of triglycerides relate to their properties?
• High ratio of carbon-hydrogen bonds make them an excellent energy source • Low mass to energy ratio- animals don’t have to carry a heavy energy store around. • Non-polar molecules are insoluble in water so they do not affect osmosis in cells. • High ratio of hydrogen to oxygen atoms so water released when trigylcerides are oxidised. Good for animals in deserts.
Identify the molecule
Monounsaturated fatty acid
Identify the molecule
Phosphate molecule
What state do monounsaturated and polyunsaturated fats take at room temperature?
Liquid - they are oils.
What is mean by a saturated fatty acid?
A fatty acid that contains no double bonds between the carbon atoms
Identify the molecule
Glycerol
Phospholipids are p___________ molecules
polar
What state do saturated lipids take at room temperature?
Solid - they are fats
What is meant by a polyunsaturated fatty acid?
A fatty acid that contains more than 1 double bond between its carbon atoms.
What does hydrophilic mean?
attracted to water
What type of bond forms between glycerol and fatty acid molecules?
Ester bond
Identify the molecule
Triglyceride
Identify the molecule
Saturated fatty acid
What type of reaction takes place when a fatty acid molecule is removed from a glycerol molecule?
Hydrolysis
What type of reaction takes place when a glycerol molecule joins with a fatty acid molecule?
Condensation reaction
Describe how you would carry out an emulsion test for lipids
The emulsion test for lipids: • Add 2cm3 of food and add to a test tube. • Add 5 cm3 of ethanol • Shake the tube thoroughly to dissolve any lipid. • Add 5cm3 of water and shake gently • A cloudy-white colour indicates a positive result.
Which part of a phospholipid is hydrophobic?
The fatty acid ‘tails’
What decides the properties of different fats and oils?
Variations in their fatty acid chains
List the roles of lipids in living organisms.
• Cell membranes • Energy store • Waterproofing • Heat insulation • Electrical insulation • Protection of organs e.g. kidneys
Why are triglycerides called triglycerides?
They contain 1 glycerol molecule (glyceride) and 3 fatty acids (tri)