Biological Molecules: Lipids Flashcards
(15 cards)
What is a lipid
Lipids are biological macromolecules made up of carbon, hydrogen and oxygen atoms.
What are triglycerides made up of
Lipids are most often triglycerides, which are made up of 3 fatty acids and glycerol
What do fatty acid molecules have
They have long tails of hydrocarbon.
What quality does hydrocarbon ‘tails’ give to fatty acids?
It makes them insoluble in water because the tails are hydrophobic.
What varies in a fatty acid?
All fatty acids have the same basic structure, but it is the hydrocarbon tail that varies.
Explain how a triglyceride is formed
A fatty acid joins to a glycerol molecule via an ester bond through a condensation reaction. This happens twice more to form a triglyceride.
Name the types of fatty acids
Saturated, unsaturated and polyunsaturated
Explain the difference between the types of fatty acids
SATURATED - They don’t have any double bonds between the carbon atoms.
UNSATURATED - They have one double bond between carbon atoms, causing the chain to kink
POLYUNSATURATED - They have more than one double bond between the carbon atoms, causing the chain to kink
How are phospholipids similar to triglycerides?
Phospholipids have one of their fatty acid molecules replaced by a phosphate group, and are used in cell membranes, whilst triglycerides are not found in the cell membrane, and have three fatty acids.
Why are phospholipids hydrophilic?
Because the phosphate group is hydrophilic.
Why are phospholipids used in cell membranes?
Because they form a bilayer membrane. The hydrophilic heads face the outside, attracted by the surrounding water, and the hydrophobic tails face inwards, making the centre of the bilayer hydrophobic. This means that water-soluble substances cannot pass through it, effectively controlling what enters and leaves cells.
What are triglycerides used for?
Energy storage molecules
How are triglycerides adapted to be used as an energy store?
1) The long hydrocarbon tails contains lots of chemical energy that is released when broken down
2) They are insoluble, so don’t affect water potential of the cell and cause water to enter by osmosis
3) They clump together because of the hydrophobic tails, shielding themselves
What test could you do to find out if there is any fat present in a food?
The emulsion test
Explain how you would use the emulsion test to find out if there is any fat present in a particular food?
1) Shake the test substance with ethanol till it dissolves, then pour the solution into water
2) Any lipid will show as a milky emulsion
3) The more lipid that is present, the milkier the colour will be
