Secondary protein structure

contiguous amino acids

next to each other in sequence

2 types of secondary structure

alpha helix and beta sheet

a helix - made of how many amino acids

5-40

how many amino acids per turn in a-helix

3.6

vertical distance between amino acids

0.15nm

pitch of a-helix/turn length

0.54nm

formula for a-helix

C=O group of a.a. N is bonded to N-H group of a.a. N+4

what is beta sheet formed from

noncontinuous regions of polypeptide chain, regions are called beta strands

parallel beta sheet

strands run in the same direction - H bonds evenly spaced within sheet

antiparallel beta sheet

strands run in opposite directions - narrowly spaced H bond pairs separated by larger gap

why are beta sheets called pleated

alpha carbons and side chains alternate whether they lie above or below the plane of the chain

loop regions

link secondary structures

long loops - random coils, highly flexible. short loop regions - hairpin loops/beta turns - they connect antiparallel strands

what connects parallel strands

alpha helix - called a beta-alpha-beta motif

crosses beta sheet from one edge to another

glycosylation

modifying proteins by adding larger molecules