Amino Acids and Protein Structure Flashcards
What are the X3 features of a peptide bond which makes them similar to double bonds?
1) the C-N bond length is shorter than a normal single bond length
2) the bond is rigid so can not rotate
3) there is a trans-arrangement of the R groups (alternately facing)
What charge on what molecule of the amino acids allows hydrogen bonding with other polar groups in a peptide chain?
The delta minus charge on the oxygen and the delta positive charge on the nitrogen (both part of the peptide bond)
What are the X2 ends of a peptide called, which is which?
What is the direction of polypeptide synthesis?
There is a N-terminus and a C-terminus
N = the amine group end
C = the carboxyl group end
Polypeptides are synthesised from N-terminus to C-terminus
What are the X4 levels of structure a peptide can have?
1) primary
= simple chain of A.A’s
2) secondary
= the folding of a peptide chain in itself to form alpha helixes and beta pleated sheets held by hydrogen bonds
3) tertiary
= further folding of the chain upon itself
4) quaternary
= multiple polypeptides joined together
What allows hydrogen bonds to form in alpha helixes?
How many spaces apart are the molecules which bond to form these structures?
What type of helix does this form?
How many residues per turn in the helix?
It is hydrogen bonding between the oxygen of the carbonyl group and every 4th H of the N-H.
This forms a regular right handed helix
There are 3.6 residues per turn
What is the structure of collagen?
Is this left or right handed?
It is a triple helix.
It is left handed in orientation.
What is a super secondary structure?
Various set combinations of alpha helixes pleated sheets in a polypeptides secondary structure.
Name some supersecondary structure examples?
- beta sandwich
- rossman fold
What is the only force stabilising proteins that is covalent?
Disulphide bridges
Name a protein misfolding disease?
Sickle cell anaemia
