Peptide Bond and Protein Structure Flashcards
What are the four different levels of protein structure?
Primary
Secondary
Tertiary
Quaternary
What does the side chain of an amino acid determine?
It determines the reactivity of the amino acid
When are peptide bonds formed?
They are formed when two amino acids come together
How are amino acids coordinated with respect to their neighbours?
Each amino acid is trans to each neighbour
What is the primary structure of an amino acid?
Peptide bonds link amino acids together
What is the secondary structure of an amino acid?
Hydrogen bonds between the backbone
What is the tertiary structure of an amino acid?
Side chain interactions
What is the quaternary structure of an amino acid?
Subunit-subunit interactions
What is the direction of the primary structure?
N-terminal -> C-terminal end of protein
What happens in order for secondary folding to occur?
There is local folding of the polypeptide chains into regular patterns such as a helix or sheet
What causes secondary folding to occur?
2
Hydrogen bonding between different amino acids in the backbone
The amide hydrogen of one AA and the carbonyl oxygen of another AA
What are the core secondary structures?
Alpha helix
Beta sheet
What are the two types of beta sheets?
Antiparallel B-sheets
Parallel B-sheets
What are antiparallel B-sheets?
3
Successive B-strands alternate directions
N-terminus of one strand is adjacent to the C-terminus of the next
H-bonds are linear -> strong
What are parallel B sheets?
The N-termini of successive strands are in the same direction
N-terminus of one strand is adjacent to the N terminus of the next
What happens in a tertiary structure?
There is overall folding of a single polypeptide chain
What side chains stick the tertiary structure together?
5
Hydrogen bonds
Salt bridges
Van der Walls interactions
Hydrophobic interactions
Disulphide bridges
What is a disulphide bond?
A covalent link between two SH groups of two cysteines
Why are disulphide bridges important?
They are important for stabilisation of the overall structure and flexibility
What is a quaternary structure made of?
made of more than one polypeptide
What is the most simple form of a quaternary structure?
A dimer
What are the three different types of quaternary structures?
Dimer
Tetramer
Hexamer
What is the resonance of a peptide bond?
A peptide bond is shifting back and forth between different states and the average is usually observed
What are the two ways a peptide bond can be formed?
A cis bond
A trans bond
