B pleated Sheets Flashcards
What is a B strand
The backbone of the polypeptide chain is extended or stretched out into a zigzag structure
What is a B sheet
Multiple B sheets arranged side by side
What stabilises the B sheets
The interchain Hydrogen bonds between peptide linkages in adjacent polypeptide chains
The individual segments that form a B sheet are usually nearby in what and distant in what
Nearby in a polypeptide chain but distant in the linear amino acid sequence
The R groups of adjacent amino acids do what and what does this create
Protude from the zigzag structure and create an alternating pattern
Are B sheets formed between parallel or anti parallel B strands
Both
How do antiparallel and parallel formations differ
The repeat period is shorter for parallel and hydrogen bonds are different
The R groups on the touching surfaces when 2 or more B sheets are layered close together must be what
Small
Example: in silk, rich in Gly and Ala and they have small R groups
Describe the anti parallel and parallel formation
Anti parallel has hydrogen bonds going straight down whereas parallel hydrogen bonds have to go diagonal
Is anti parallel or parallel more stable?
Anti Parallel.
Parallel bonds are at an angle so the bonds are longer and weaker
An anti parallel sheet forms when what happens and what is this called
when a polypeptide chain sharply reverses direction - B turn
How is the sharp turn formed
when there are 2 consecutive proline residues as they create an angled kink forcing the chain to bend
a B turn involves what
4 amino acids and is a 180 turn
How is the hydrogen bond formed in a b turn
carbonyl oxygen of 1st residue forms a H bonds with amide hydrogen of the 4th
What 2 amino acids often occur in a B turn
Glycine and Proline
