AS Biology Core Principles Lipids
Aims o Elements of lipids o Structure of glycerol & fatty acids o Condensation reactions to form triglycerides o Phospholipids
Introduction to lipids
o Lipids contain the elements carbon, hydrogen and oxygen. o They have numerous functions, primarily energy stores in animals and plants. o Lipids consist of two types of molecules - glycerol & fatty acids.
Glycerol o A molecule of glycerol is made up of three carbon atoms. o Each of these has a hydroxyl group attached to it. o Hydrogen atoms occupy the remaining positions.
Fatty Acids
o A single fatty acid molecule contains an acid (COOH) group attached to a hydrocarbon chain. o Hydrocarbon usually denoted by the letter ’R’. o Saturated = If every carbon atom in the chain is joined by a single C-C bond. o Unsaturated = at least one C=C bond. o Polyunsaturated = many double bonds. o Most animal fats are saturated while most plant fats are unsaturated.
Triglycerides
o A triglyceride molecule is made of a glycerol molecule and three fatty acids. o The molecules join together through the process of condensation losing a molecule of water each time a link is made. o The link between the glycerol molecule & each fatty acid is an ‘Ester Link’. o The fatty acids in a lipid molecule can differ in length and can be saturated or unsaturated.
Triglycerides
Phospholipids o In phospholipids one of the fatty acids of a triglyceride is substituted by a phosphate group.
Phospholipids
Lipids & water o Triglycerides and phospholipids have hydrophobic and hydrophilic groups. oWhat does this mean? oTo what use is this feature put in biology?
More Info o To make further notes on Lipids : oPages 11 & 12 in Collins oPages Roberts owww.mrothery.co.ukwww.mrothery.co.uk owww.learn.co.ukwww.learn.co.uk owww.bbc.co.uk/education/asguru/