Biological Molecules- Lipids Flashcards
What is the structure of triglycerides?
One molecule of glycerol and three fatty acids attached
How do you describe fatty acid molecules?
They have long ‘tails’ made of hydrocarbons, tails are hydrophobic so repel water molecules, make lipids insoluble in water
What is the basic structure of a fatty acid?
A carbon atom that links fatty acid to glycerol and a variable R group
How are triglycerides formed?
Three condensation reactions between glycerol and each of the fatty acids
What bond is formed between glycerol and fatty acids?
Ester bonds
What are saturated fatty acids?
They don’t have any double bonds between carbon atoms
What are unsaturated fatty acids?
They have at least one double bond between carbon atoms
What lipids are found in cell membranes?
Phospholipids
How are phospholipids different to triglycerides?
One fatty acid molecules is replaced by a phosphate group
Which parts of the phospholipid is hydrophilic and hydrophobic?
Phosphate group is hydrophilic and fatty acid tails are hydrophobic
Why are triglycerides good for energy storage?
- Long hydrocarbon tails of fatty acids contain lots of chemical energy so a lot of energy is released when broken down
- Insoluble so don’t affect water potential of cell so water can’t enter by osmosis
What is a phospholipids role in the cell membrane?
They make up a bilayer and control what enters and leaves a cell
How is the bilayer formed?
Hydrophilic phosphate heads facing outwards and hydrophobic fatty acid tails facing inwards
What does the centre of the bilayer being hydrophobic mean?
Water soluble substances can’t easily pass through the membrane
How do you test for lipids?
Emulsion test
- Shake test substance with ethanol
- Pour solution into water
- Positive result= forms milky emulsion, a more noticeable colour means there is more lipid present
