Lipids Chapter 3.5 Flashcards
Lipids
Fats and oils. Fats are solid, oils are liquid
Triglycerides
Made combining one glycerol molecule and 3 fatty acids
Lipids are non-polar
This is because the electrons between the bonds are more evenly spread than in polar molecules, this also means lipids are insoluble
Glycerol
It belongs to the alcohols group
Fatty acids
Carboxyl groups with a hydrocarbon chain attached to it
Saturated
This is when the fatty acid chains have no double bonds so all the carbons have their maximum number of bonds, is compact so is a solid
Monounsaturated
Only one double bond which makes a little kink
Polyunsaturated
More than one double bond in the fatty acid chains which creates bends in the molecule. This means it’s not as compact as is probably a liquid
Phospholipids
These are modified triglycerides that have a phosphate group and 2 fatty acid chains. Contains phosphate ions that have extra electrons so is soluble in water, the rest of the molecule isn’t.
Structure of a phospholipid
It has a charged phosphate head that is hydrophilic so is attracted to water and it has 2 fatty acid tails that are hydrophobic so repel water
Surfacants
Phospholipids are weird on water. The phosphate head is submerged in the water while the tails stick out this means they are surface active agents or surfacants. Great for forming cell membranes
Sterols
Also called steroid alcohols aren’t fats or oils they have a 4 carbon ring with a hydroxyl group on the end. This also means it has a hydrophilic/hydrophobic structure
Cholesterol
This is a type of sterol that is very useful in the body. Important in forming cell membranes as it can go in between the phospholipds to make the structure more solid and also maintain the fluidity
Biological uses of lipids
Great for membrane formation
Hormone production
Electrical insulation
Waterproofing
Biological uses of triglycerides
Great for insulation
Cushioning of vital organs
Buoyancy in marine animals
Emulsion test
Add ethanol to sample and mix
Add water and then shake
Then see if white precipitate forms, if so it’s positive
Beta oxidation
This is when triglycerides are used for respiration. Its hydrolysed into fatty acids and glycerol. The glycerol is oxidised by beta-oxidation to get glucose needed for respiration.
Why is lipid a better energy store than carbohydrates?
Because they have more hydrogens and fewer oxygens so less water is associated. Also, they can be fully oxidised whereas carbs can only be partially oxidised.
Iodine Number
Test for the degree of unsaturation. Iodine is added to lipid and if it’s unsaturated the iodine will break the double bond and attach to the hydrocarbon chain. This means it will go from brown to colourless.
Hydrogenation
Adding hydrogen to the unsaturated lipid to make it more solid.
