Chapter 4

Question 1

peptide bonds in proteins

Answer 1

trans

Question 2

rotation in peptide chain

Answer 2

two covalent bonds of Ca-C (psi) and N-Ca(phi)

Question 3

globular shapes

Answer 3

polypeptide chain must frequently reverse direction

Question 4

globular proteins

Answer 4

compact, spherical, and conduct most enzymatic activity

Question 5

fibrous proteins

Answer 5

extended, insoluble, and usually fill structural roles in the cell

Question 6

intrinsically disordered protein

Answer 6

lack defined secondary and tertiary structure until bound

Question 7

quaternary structure

Answer 7

assembly of individual polypeptides into a larger functional cluster

Question 8

denaturation

Answer 8

loss of structural integrity with accompanying loss of activity

Question 9

proteins can be denatured by

Answer 9

-heat or cold
-pH extremes
-organic solvents
-chaotropic agents

Question 10

anfinsen ribonuclease refolding experiment

Answer 10

-urea in the presence of 2-mercaptoethanol fully denatures ribonuclease
- when they are removed, protein refolds and current disulfide bonds are reformed
- protein sequence alone determines the native conformation

Question 11

chaperones

Answer 11

do not actively promote the folding of the substrate protein but prevent aggregation of unfolded peptides