Protein

Key Stage 3

Meaning

Proteins are molecules in our diet that are used by our bodies for growth and repair.

About Proteins

There are many different proteins.

Protein is used to build muscles and repair injuries.

Not enough protein can cause a disease called Kwashiorkor.

Sources of Protein

We can eat any of these foods to get enough protein.

Meat provides lots of protein for a balanced diet.	You can help keep your diet balanced by eating lots of different beans.	Nuts are the seeds of trees and are part of a balanced diet.	There are many different kinds of peas that can help make sure you have a balanced diet.

Testing For Protein

Adding protein to Biuret solution will cause the solution to turn purple.

Method

1. Take a small sample of food and dissolve it in water.

2. Add some Biuret to the solution.

3. If it turns from blue to purple then the food contained protein.

This Biuret has turned purple, indicating protein is present.

Key Stage 4

Meaning

Proteins, also known as polypeptides, are large polymer molecules made from amino acids that are used by our bodies for growth and repair.

About Proteins

Proteins (polypeptides) are formed in polymerisation reactions of Amino Acids (peptides).

Proteins are broken down by our digestive systems into amino acids which are then transported around the body by our blood.

Cells build new proteins from amino acids in a process called protein synthesis which takes place at the ribosomes in cells.

Protein is essential to build enzymes which control the metabolic processes inside the cell.

A single protein can be made of millions of amino acids bonded together.

This diagram represents an amino acid and a small protein made of 3 different amino acids.

Sources of Protein

We can eat any of these foods to get enough protein.

Meat provides lots of protein for a balanced diet.	You can help keep your diet balanced by eating lots of different beans.	Nuts are the seeds of trees and are part of a balanced diet.	There are many different kinds of peas that can help make sure you have a balanced diet.

Testing For Protein

Adding protein to Biuret solution will cause the solution to turn purple.

Method

1. Take a small sample of food and dissolve it in water.

2. Add some Biuret to the solution.

3. If it turns from blue to purple then the food contained protein.

This Biuret has turned purple, indicating protein is present.

References

AQA

Polypeptide, page 251, GCSE Chemistry; Student Book, Collins, AQA

Polypeptides, page 173, GCSE Chemistry; Third Edition, Oxford University Press, AQA

Polypeptides, pages 192-3, GCSE Chemistry, Hodder, AQA