Lipids Flashcards
Why are lipids different from proteins and carbohydrates?
They’re not polymers formed from long chains of monomers
What are Lipids made from?
Hydrocarbons
What are hydrocarbons?
Molecules that contain only hydrogen and carbon atoms
What are the 2 types of lipids?
Triglycerides
Phospholipids
What is the structure of triglycerides?
1 molecule of glycerol with 3 fatty acids attached
What is the structure of fatty acid molecules?
How does it make lipids insoluble in water?
Have long ‘tails’ made of hydrocarbons
Tails are ‘hydrophobic’
What does hydrophobic mean?
They repel water molecules
What are the 2 types of fatty acid?
Saturated
Unsaturated
What is the difference between the 2 types of fatty acid?
Saturated don’t have double bonds between carbon atoms
Unsaturated do
What are saturated fatty acids saturated with?
Hydrogen
What causes the chain to kink in unsaturated fatty acids?
Double bonds between carbon atoms
What reaction forms a triglyceride?
Condensation
How is a triglyceride formed?
Ester bond forms between a fatty acid and a glycerol molecule
Releasing a molecule of water
Happens twice more
What are the lipids found in cell membranes?
Phospholipids
What is the structure of a phospholipid?
Glycerol molecule
2 fatty acids
Phosphate group
What does the phosphate group do in the phospholipid?
Attracts water
What does hydrophilic mean?
Attracts water
What are triglycerides mainly used as?
Energy storage molecules
Why are triglycerides good for storage?
Long hydrocarbon tails of fatty acids contain lots of chemical energy
Why do the triglycerides bundle together as insoluble droplets in cells?
Fatty acid tails are hydrophobic
Tails face inwards, shielding themselves from water with their glycerol heads
What makes up the bilayer of cell membranes?
Phospholipids
What do cell membranes control?
What enters and leaves the cell
Why do phospholipids form a double layer?
Why does the membrane act as a barrier to water?
Phospholipid heads are hydrophilic and tails are hydrophobic so heads face out towards water on either side
Centre of bilayer is hydrophobic so water-soluble substances can’t easily pass through it
What test is used to test for lipids?
Emulsion test
How do you carry out the emulsion test?
Shake test substance with ethanol for about a minute
Pour solution into water
What does a milky emulsion in the emulsion test identify?
Lipid is present
