1.6 Proteins Flashcards
How are proteins formed?
Amino acids combine to make a polypeptide. Polypeptides combine to form proteins
How is a peptide bond formed?
In a condensation reaction between two amino acids to form a dipeptide. The peptide bond is formed between the carbon atom of one amino acid and the and the nitrogen atom of another.
What is the primary structure of an amino acid?
The sequence of amino acids in a polypeptide.
In what type of reaction do many amino acids join together to form a polypeptide?
Polymerisation
What does the primary structure of a protein determine?
The proteins shape and hence its function
What are the bonds in the bonds in the tertiary structure?
Disulphide bridges
Ionic bonds
Hydrogen bonds
Why does the chain of amino acids form an alpha helix or beta pleated sheet?
The -NH has a slight positive charge and the C–O has a slight negative charge. As a result weak hydrogen bonds can form leading to alpha helixes or beta pleated sheet
Describe disulphide bridges.
Fairly strong, not easily broken
Where are ionic bonds formed?
Between any carboxyl and amino groups that are not involved in forming peptide bonds.
Describe hydrogen bonds.
Numerous but easily broken.
What is the test for proteins?
Biuret test
Describe the test for proteins.
Add an equal volume of sodium hydroxide to the sample.
Add a few drops of dilute (0.05%) copper (II) sulphate solution and mix gently.If it turns purple from blue it means a peptide bond is present
