A - 5 - Proteins

Question 1

What is a dipeptide?

Answer 1

A molecule formed from two amino acids

Question 2

What is a polypeptide?

Answer 2

A molecule formed from more than two amino acids

Question 3

What is the general structure of an amino acid?

Answer 3

• A carboxyl group (-COOH)
• An amino group (-NH)
• An R variable group
• A carbon atom

Question 4

How many amino acids are there altogether?

Answer 4

Only 20, all living things are made up of these 20 amino acids

Question 5

How are amino acids linked together?

Answer 5

Through condensation reactions

Question 6

What is the bond formed between amino acids called?

Answer 6

Peptide bonds

Question 7

Describe the primary structure of a protein

Answer 7

The sequence of amino acids in the polypeptide chain

Question 8

Describe the secondary structure of a protein

Answer 8

- Hydrogen bonds form between the amino acids in the chain
The chain either:
- Coils into an alpha helix
or
- Folds into a beta pleated sheet

Question 9

Describe the tertiary structure of a protein

Answer 9

• The chain of amino acids is coiled or folded even more
• More bonds form including, hydrogen bonds, ionic bonds or disulphide bridges
• For proteins made from only one amino acid chain, this is the final 3D structure of the protein

Question 10

Describe the quaternary structure of a protein

Answer 10

• Some proteins are made of more than one chain of amino acids
• The quaternary structure is the way these chains are assembled together
• This is the proteins final 3D structure

Question 11

Which test is used to see if a protein is present?

Answer 11

The biuret test

Question 12

How do you carry out the biuret test? Describe the results

Answer 12

• Add sodium hydroxide solution
• Add copper(ii)sulphate solution
• If a protein is present the solution will turn purple and if not it will stay blue