Unit 1: Protein structure Flashcards
What is the primary structure of a protein ?
The individual amino acid sequence
What is the secondary structure of a protein ?
The spatial arrangement of a polypeptides backbone. e.g a-helix and b-pleated sheets
What is the tertiary structure of a protein ?
The three dimensional structure of the entire polypeptide chain
What is the quaternary structure of a protein ?
How polypeptide chains fit together to form a protein
Within a polypeptide chain, what are individual amino acids referred to as ?
Residues
How many amino acids need to be present for a polypeptide to be referred to as a protein ?
Over 50
What enzyme is used to catalyse the formation of a peptide bond ?
Peptidyl transferase
The peptide bond is polar, what does this mean ?
That the spatial arrangement of atoms is fixed and the bonds cannot rotate/ spin
What are the only 2 bonds that can rotate in a polypeptide ?
- C-NH
- C-C
What bonds are needed for primary structure of proteins ?
Covalent bonds maintain the primary structure
What bonds are needed for the secondary structure of proteins ?
Hydrogen bonds maintain the secondary structure
What 3 bonds are needed for the tertiary structure of proteins ?
- Hydrophobic
- Van der Waals
- Electrostatic bonds
What 2 bonds are needed for the quaternary structure of proteins ?
- Van der Waals
- Electrostatic bonds
What is the a-helix referred to as and what direction do the hydrogen bonds run in ?
- Twisted sheet
- H bonds run parallel to the helix axis
What is the b-sheet referred to as and what direction do the hydrogen bonds run in ?
- Flat sheet
- H bonds run perpendicular to chain direction
What are r groups and where are they found ?
- R groups influence the way proteins interact with other proteins and the environment
- R groups are pointed outward but are not used in the helix structure
What are the 2 types of b-sheet ?
- Anti parallel
- Parallel
What direction do bonds run in a parallel b-sheet ?
- All same direction
- All downwards
What direction do bonds run in an antiparallel b-sheet ?
- Alternate directions
- Down, Up, Down, Up
What are some characteristics of non polar amino acids ?
- They have very oily side chains
- Important interactions with environment
What is one characteristic of a polar amino acid ?
They have a partial positive and negative end
What are some characteristics of electrically charged amino acids ?
- Acidic AAs are negatively charged
- Basic AAs are positively charged
- Important electrostatic interactions
What are the 3 classes of amino acid R groups ?
- Non-polar
- Polar
- Electrically charged
Why is cysteine an important AA ?
It contains disulphide bonds that are important for protein structure
