Secondary Protein Structure Flashcards
Is a disulphide bridge a bond or a force?
A bond, the only one in proteins.
- Contributes towards the overall shape of the protein
What does restricted rotation around the peptide bond cause?
Restricted rotation around the peptide bond gives SECONDARY structure
What further limitations are there when a polypeptide forms?
structure formation within certain boundaries
∴ avoids the sampling of all random conformations
∴ could lead to misfolding
What side does the Phi (Φ) angle work on and what way can it rotate?
N side - LEFT
Rotates down to the right
What side does the Psi (Ψ) angle work on and what way can it rotate?
C side - RIGHT
Rotates up to the right
What structures form from the dihedral angles of the peptide bonds?
Alpha Helix (right-handed) Beta Strands
What atoms can Hydrogen bonds form between?
H and O or N (must have lone pairs)
What are the phi and psi angles in an alpha helix?
Phi (Φ) = -57 degrees
Psi (Ψ) = -47 degrees
What are alpha helixes bonded and stabilised by?
Hydrogen Bonds
Which number + group of atoms are Hydrogen bonded to the CO residue?
The 4th NH residue
How many amino acids are there in one complete turn of the alpha helix?
3.6 amino acids
What direction does the alpha helix twist?
Clockwise
What shape are the peptide bonds?
Trans + Planar
What 2 kinds of beta pleated sheets are there?
Parallel = 2 amino acid chains connected by H-bonds Anti-parallel = strands run in opposing directions
What makes the beta sheets pleated?
tetrahedral alpha carbon
+
planar peptide bond
therefore extended structure is pleated
What is an alpha helix?
Repeated units of phi and psi angles
What is a beta pleated sheet?
A peptide in its extended form (5 or more amino acids)
What do turns and bends do?
Change directions in which the sheets/helices run.
How many types of B-turn are there?
2
What are complex alpha helices?
Alpha helix that can wind around each other to form ‘coiled coils’ (like a rope) that are very stable (for support).
What are complex alpha helices found in?
Fibrous Proteins like keratin and myosin
What do the connection and folds of the SECONDARY structure form?
The TERTIARY structure
