Lipids Flashcards
Describe the structure of a triglyceride molecule
1 Glycerol, 3 Fatty Acids
Describe the structure of a fatty acid.
- Long ‘tails’ made of hydrocarbons that are hydrophobic.
- These make lipids insoluble in water.
- Fatty acids all have same basic structure, but hydrocarbon tail varies.
- Carbon atom links fatty acid to glycerol.
How are triglycerides formed?
By condensation reactions.
- A molecule of water is released as the ester bond is formed between fatty acid and glycerol.
- This process happens twice more to form a triglyceride
What are the two kinds of fatty acids?
Saturated and Unsaturated
What is the structural difference between saturated and unsaturated fatty acids?
They have different hydrocarbon tails.
- Saturated fatty acids dont have any double bonds between their carbon atoms. The fatty acid is ‘saturated’ with hydrogen
- Unsaturated fatty acids have at least one double bond between carbon atoms.
- This causes the chain to kink.
What lipids are found in cell membranes?
Phospholipids.
Describe the structure of phospholipids.
1 Glycerol, 2 Fatty acids, 1 phosphate group.
- the phosphate group is hydrophilic (attracts water). The fatty acid tails are hydrophobic (repel water).
Why does the structure of triglycerides help them to be good energy storage molecules?
- Lipids contain twice as much energy gram for gram as carbohydrates (hydrocarbon tails contain lots of energy)
- Insoluble, so dont affect water potential. Triglycerides clump together as insoluble droplets bc fatty acid tails are hydrophobic, so tails face inwards protected by glycerol heads.
How do phospholipids form the bilayer of cell membranes?
- Their heads are hydrophilic & tails are hydrophobic, so they form a double layer with their heads facing out towards the water on either side.
- Centre of bilayer is hydrophobic so water-soluble substances cant easily pass though it-membrane acts as a barrier to these substances.
How to test for lipids?
Emulsion test.
- shake substance with ethanol for a minute so it dissolves, then pour solution into water
- any lipid will show up as a milky emulsion
- more lipid there is, more noticeable milky colour will be.