Protein Interactions (AQA A Level Biology): Revision Note
Exam code: 7402
Proteins: interactions & bonds
A polypeptide chain will fold differently, into its tertiary structure, due to the interactions (and hence the bonds that form) between R groups
Each of the twenty amino acids that make up proteins has a unique R group, and therefore, many different interactions can occur, creating a vast range of protein configurations and therefore functions
Within tertiary structured proteins are the following bonds:
Strong covalent disulfide
Weak hydrophobic interactions
Weak hydrogen
Ionic
Disulfide
Disulfide bonds (also known as disulfide bridges) are strong covalent bonds that form between two cysteine R groups (this is the only amino acid with an available sulfur atom in its R group)
These bonds are the strongest within a protein, but occur less frequently, and help stabilise the proteins
They can be broken by reduction
Disulfide bonds are common in proteins that are secreted from cells e.g. insulin
Ionic
Ionic bonds form between positively charged (amine group -NH3+) and negatively charged (carboxylic acid -COO-) R groups
Ionic bonds are stronger than hydrogen bonds, but they are not common
These bonds are broken by pH changes
Hydrogen
Hydrogen bonds form between strongly polar R groups
These are the weakest bonds that form, but the most common, as they form between a wide variety of R groups
Examiner Tips and Tricks
You need to be able to determine which bonds are found in tertiary structures and recognise them in diagrams.
You've read 0 of your 5 free revision notes this week
Unlock more, it's free!
Did this page help you?