AS Biology Core Principles Lipids Aims Elements of

AS Biology Core Principles Lipids

Aims Elements of lipids o Structure of glycerol & fatty acids o Condensation reactions to form triglycerides o Phospholipids o

Introduction to lipids

Introduction to lipids 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. o

Glycerol 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. o

Fatty Acids

Fatty Acids o o o A single fatty acid molecule contains an acid (COOH) group attached to a hydrocarbon chain. Hydrocarbon usually denoted by the letter ’R’. Saturated = If every carbon atom in the chain is joined by a single C-C bond. Unsaturated = at least one C=C bond. Polyunsaturated = many double bonds. Most animal fats are saturated while most plant fats are unsaturated.

Triglycerides

Triglycerides 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. o

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. o What does this mean? o To what use is this feature put in biology?

More Info o To make further notes on Lipids : o Pages 11 & 12 in Collins o Pages 69 - 71 Roberts o www. mrothery. co. uk o www. learn. co. uk o www. bbc. co. uk/education/asguru/

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