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Biological molecules





A nutrient is a substance which is needed for growth, repair and metabolism.

The three main nutrients are:

- carbohydrates

- proteins

- lipids (fats and oils)

These nutrients are all examples of organic chemicals.

This means that they all contain carbon atoms, covalently bonded to the atoms of other elements. [1]


Lipids are fats and oils.

Lipids are large molecules made from smaller units of fatty acids and glycerol.

The structure of a lipid molecule

In the diagram, you can see how three long chains of carbon atoms are attached to a glycerol molecule, with its three carbon atoms.

Together they combine to make one lipid molecule. [3]


Proteins are large molecules made from smaller units of amino acids.

The structure of two amino acids [5]

Chemical elements that make up ...

Carbohydrates - Oxygen, Carbon, Hydrogen

Lipids (Fats) - Oxygen, Carbon, Hydrogen

Proteins - Oxygen, Carbon, Hydrogen, Nitrogen [2]


The basic units of carbohydrates are simple sugars, such as glucose and fructose.

These are also called monosaccharides.


Glucose and fructose have the same molecular formula, C6H12O6. However, their structure is different.

1. The structure of glucose

2. The structure of fructose


Sucrose is a disaccharide.

It consists of two monosaccharides, glucose and fructose, joined together.


Starch (found in plants) and glycogen (found in animals) are polysaccharides.

They consist of many glucose molecules joined together. [4]







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