3.1.3 Lipids Flashcards
What are triglycerides made of?
They have one molecule of glycerol with three fatty acids attached to it.
Fatty acid molecules have long ‘tails’ made of what?
Hydrocarbons
The tails of fatty acid molecules are what?
Hydrophobic
What does it mean if something is hydrophobic?
It repels water molecules
The hydrophobic tails of fatty acids make them lipids what in water?
Insoluble
A fatty acid is attached to a glycerol molecule by what type of bond?
Ester bond
What are the two kinds of fatty acids?
Saturated and unsaturated
What is the difference between saturated and unsaturated fatty acids?
Hydrocarbon tails (R group)
What test do you use to test for the presence of lipids?
Emulsion test
How do you carry out the emulsion test?
1) Shake the test substance with ethanol for about a minute so that it dissolves, then pour the solution into water.
2) Any lipid will show up as a milky emulsion
3) The more lipid there is, the more noticeable the milky colour will be
What are triglycerides mainly used as?
Energy storage molecules
Triglycerides are mainly used as energy storage molecules. Why are they good for this?
1) The long hydrocarbon tails of the fatty acids contain lots of chemical energy - a load of energy is released when they’re broken down. Because of these tails, lipids contain about twice as much energy per gram as carbohydrates.
2) They’re insoluble, so they don’t affect the water potential of the cell and cause water to enter the cells by osmosis. The triglycerides clump together as insoluble droplets in cells because the fatty acid tails are hydrophobic - the tails face inwards, shielding themselves from water with their glycerol heads.
The lipids found in cell membranes aren’t triglycerides. What are they?
Phospholipids.
Phospholipids are very similar to triglycerides.
