3.1.4 Proteins

What are ‘amino acids’?

The monomers from which proteins are made.

What is the general structure of an amino acid?

A carbon atom bonded to a carboxylic acid, hydrogen, an amine group and a variable group.

Define ‘dipeptide’ and ‘polypeptide’.

Dipeptide - when two amino acids join together.
Polypeptide - when more than two amino acids join together.

What reaction links amino acids together?

Condensation reaction - where a water molecule is released.

What are the bonds formed in this reaction called?

Peptide bonds

Describe the term ‘primary structure’

Sequence of amino acids in the polypeptide chain.

Describe the term ‘secondary structure’

Hydrogen bonds form between the amino acids in the chain.

Either:

• coils into alpha (α) helix

• folds into beta (β) pleated sheet

Describe the term ‘tertiary structure’

Amino acids are coiled or folded further.

More bonds form between polypeptide chains.

• Hydrogen bonds

• Ionic bonds

• Disulphide bridges

  • forms when 2 molecules of cysteine come close together.

    • sulphur atoms in both molecules bond to each other

Describe the term ‘quaternary structure’

The arrangement of multiple polypeptide chains held together by bonds.