LIPIDS Flashcards
What is a lipid
Macromolecules which contain carbon, hydrogen and oxygen atoms. However, unlike carbohydrates lipids contain a lower proportion of oxygen
Are lipids polar/hydrophobic
Non-polar and hydrophobic (insoluble in water)
Two types of lipid
There are two groups of lipid that you need to know:
Triglycerides (the main component of fats and oils)
Phospholipids
What are triglycerides
Triglycerides
Are non-polar, hydrophobic molecules
The monomers are glycerol and fatty acids
What is glycerol
Glycerol is an alcohol (an organic molecule that contains a hydroxyl group bonded to a carbon atom)
What so fatty acids contain at one end
Fatty acids contain a methyl group at one end of a hydrocarbon chain known as the R group (chains of hydrogens bonded to carbon atoms, typically 4 to 24 carbons long) and at the other is a carboxyl group
formula for fatty acid
The shorthand chemical formula for a fatty acid is RCOOH
What about fatty acids can vary
Fatty acids can vary in two ways:
Length of the hydrocarbon chain (R group)
Two types of chain
The fatty acid chain (R group) may be saturated (mainly in animal fat) or unsaturated (mainly vegetable oils, although there are exceptions e.g. coconut and palm oil)
what makes it mono or poly unsaturated
Unsaturated fatty acids can be mono or poly-unsaturated:
If H atoms are on the same side of the double bond they are cis-fatty acids and are metabolised by enzymes
If H atoms are on opposite sides of the double bond they are trans-fatty acids and cannot form enzyme-substrate complexes, therefore, are not metabolised.
They are linked with coronary heart disease
How are triglycerides formed
Triglycerides are formed by esterification
An ester bond forms when a hydroxyl (-OH) group on glycerol bonds with the carboxyl (-COOH) group of the fatty acid:
An H from glycerol combines with an OH from the fatty acid to make water
The formation of an ester bond is a condensation reaction
What is released during condensation
For each ester bond formed a water molecule is released
How many water released by glycerol to fatty acid
Three fatty acids join to one glycerol molecule to form a triglyceride
Therefore for one triglyceride to form, three water molecules are released
