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CIE AS Biology (9700) 2019-2021 Resources

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CIE AS Biology (9700) 2019-2021 Revision Notes

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2. Biological Molecules

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CIE AS Biology (9700) 2019-2021 Resources

REVISION NOTES 

 

  TOPIC QUESTIONS 

 

  PAST PAPERS

Page 33

2.2.5 TRIGLYCERIDES

Triglycerides: Basics

Lipids

Macromolecules which contain carbon, hydrogen and oxygen atoms. However, unlike

carbohydrates lipids contain a lower proportion of oxygen

Non-polar and hydrophobic (insoluble in water)

Different types:

Fats and Oils (composed mainly of triglycerides)

Phospholipids

Steroids and waxes (considered lipids as they are hydrophobic thus insoluble in water)

Triglycerides

Are non-polar, hydrophobic molecules

The monomers are glycerol and fatty acids

Glycerol is an alcohol (an organic molecule that contains a hydroxyl group bonded to a

carbon atom)

Fatty acids contain a methyl group at one end of a hydrocarbon chain (chains of hydrogens

bonded to carbon atoms, typically 4 to 24 carbons long) and at the other is a carboxyl group

Fatty acids can vary in two ways:

Length of the hydrocarbon chain

The fatty acid may be saturated (mainly in animal fat) or unsaturated (mainly

vegetable oils, although there are exceptions e.g. coconut and palm oil)

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

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