SFP2: Protein Structure Flashcards
Name three functional roles of proteins
- enzymes and catalytic
- structural elements
- carriers
- hormones and effectors
- receptors
- movement
- defence
- transcription factors
- chaperones
- storage
What is the human proteome
The total number of different proteins (estimated >100,000)
What is protein molecular weight commonly expressed in?
Daltons (1Da=1amu)
This is absolute molecular weight - mass (in g) of 1 mole
What does amphoteric mean?
Having the characteristics of an acid and a base
What does zwitteronic mean?
A molecule carrying both a positive and negative charge
Is the D or L isoform of an amino acid found in proteins?
L-isomers
Which amino acid is the only one with no chiral centre?
Glycine (because the R group is a hydrogen)
What does the peptide bond form between?
Between alpha-carbonyl and alpha-amino group of amino acids
What is a residue?
An amino acid in a polypeptide
What is the molecular weight of an amino acid in daltons?
120Da
What does the rigid planar nature of peptide bond influence?
Protein folding
What bonds along the backbone are the only bonds that can rotate?
The bonds around the C-N- this allows the polypeptide to fold into regular structures
Is trans or cis conformation favoured?
Trans as there is less repulsion between atoms connected to Calpha
What is primary structure of an amino acid?
Amino acid sequence, results from covalent bonds
How does a circular protein occur?
When N terminus of a protein is condensed with the C terminus
What is the secondary structure of a protein?
Local conformation of a polypeptide chain
What are the three basic common units of secondary structure in globular proteins?
Alpha-helix
Beta sheets
Turns
What is tertiary structure?
Overall folding of a polypeptide chain (spatial arrangement of amino acids which are far apart in the linear sequence)
What bonds is tertiary structure stabilised by?
Hydrophobic
Van der walls
Hydrogen bonds
Electrostatic bonds
What is Quarternary structure
Non-covalent association of more than one polypeptide unit (or subunit)
What is alpha helix
hydrogen bonds between main chain residues (1-5, 2-6 etc.)
3.6 AA residues / turn
Side chains on outside of helix
Right handed ‘screw-thread’
What is a beta sheet
Can be ‘parallel’ or ‘anti-parallel’
Hydrogen bonds between C double bond P and N-H from main chain
Do polar or non-polar amino side chains position to the inside of an amino acid?
Non-polar on the inside -> hydrophobic core
What are turns?
Connect regions of helix/beta sheet - hydrogen bonds
Beta turns have hairpin structure where amino acid (n) hydrogen bonded to amino acid (n+3)
