BIOMG 3300 - Unit 2 Study Questions
Solved 100% Correct
what is the meaning of the phrase "to denature a protein"?
partial or complete unfolding of the specific native conformation of a polypeptide chain,
protein, or nucleic acid such that the function of the molecule is lost
how can the denatured and reduced ribonuclease be converted to its native form?
by removing the urea and β-mercaptoethanol
why did the “Anfinsen” experiment prove that the primary sequence specifies the native
structure?
once you remove the urea and β-mercaptoethanol, the protein folds back to its native structure
(the primary structure of a polypeptide chain contains all the information required to fold the
chain into its native 3D structure)
true or false. different amino acid sequences can generate similar protein folds.
true
what is a molecular chaperone?
any of the several classes of proteins or protein complexes that catalyze the accurate folding
of proteins in all cells by interacting with partially or improperly folded proteins
what are the two major families of chaperones?
Hsp70 and chaperonins
what is a chaperonin?
a complex of proteins that are required for the folding of some cellular proteins that don't fold
spontaneously
most proteins that contain disulfide bonds are ________.
extracellular
in living cells, discuss the role of protein disulfide isomerase (PDI) on protein folding.
PDI is an enzyme that catalyzes the interchange of disulfide bond until the bonds of the native
conformation are formed (chaperone protein)
discuss the role of peptide prolyl cis-trans isomerase (PPI) in protein folding.
, PPI catalyzes the interconversion of the cis and trans isomers of peptide bonds formed by
Pro residues (chaperone protein)
free energy funnel diagram
depicts decrease in entropy of protein as it folds.
from random coil polypeptides, protein collapses into molten globule states because of H-
bonds and hydrophobic effect, and then continues to fold from ionic and van der Waals forces.
crude extract
a solution of proteins released from cells that were broken open (the first step of
protein purification)
differential & sucrose density centrifugation
method used to prepare subcellular fractions or to isolate specific organelles where larger
particles sediment more rapidly than small particles (and soluble materials do not sediment)
fractionation
the process of separating the proteins or other components of a complex molecular mixture
into fractions based on differences in properties such as solubility, net charge, molecular
weight, or function
dialysis
removal of small molecules from a solution of a macromolecule by their diffusion through a
semi permeable membrane into a suitably buffered solution
column chromatography
- a technique where a porous solid material with appropriate chemical properties (stationary
phase) is held in a column and a buffering solution (mobile phase) migrates through it.
- takes advantage of differences in protein charge, size, binding affinity, and other properties.
ion-exchange chromatography
a process for separating complex mixtures of ionic compounds by many repeated
partitionings between a flowing phase and a stationary phase consisting of a polymeric resin
that contains fixed charged groups
on what basis are proteins separated using ion-exchange chromatography?
differences in the sign and magnitude of the net electric charge of proteins at a given pH
What is the overall charge on a protein when the pH < pI? pH = pI? pH > pI?
Solved 100% Correct
what is the meaning of the phrase "to denature a protein"?
partial or complete unfolding of the specific native conformation of a polypeptide chain,
protein, or nucleic acid such that the function of the molecule is lost
how can the denatured and reduced ribonuclease be converted to its native form?
by removing the urea and β-mercaptoethanol
why did the “Anfinsen” experiment prove that the primary sequence specifies the native
structure?
once you remove the urea and β-mercaptoethanol, the protein folds back to its native structure
(the primary structure of a polypeptide chain contains all the information required to fold the
chain into its native 3D structure)
true or false. different amino acid sequences can generate similar protein folds.
true
what is a molecular chaperone?
any of the several classes of proteins or protein complexes that catalyze the accurate folding
of proteins in all cells by interacting with partially or improperly folded proteins
what are the two major families of chaperones?
Hsp70 and chaperonins
what is a chaperonin?
a complex of proteins that are required for the folding of some cellular proteins that don't fold
spontaneously
most proteins that contain disulfide bonds are ________.
extracellular
in living cells, discuss the role of protein disulfide isomerase (PDI) on protein folding.
PDI is an enzyme that catalyzes the interchange of disulfide bond until the bonds of the native
conformation are formed (chaperone protein)
discuss the role of peptide prolyl cis-trans isomerase (PPI) in protein folding.
, PPI catalyzes the interconversion of the cis and trans isomers of peptide bonds formed by
Pro residues (chaperone protein)
free energy funnel diagram
depicts decrease in entropy of protein as it folds.
from random coil polypeptides, protein collapses into molten globule states because of H-
bonds and hydrophobic effect, and then continues to fold from ionic and van der Waals forces.
crude extract
a solution of proteins released from cells that were broken open (the first step of
protein purification)
differential & sucrose density centrifugation
method used to prepare subcellular fractions or to isolate specific organelles where larger
particles sediment more rapidly than small particles (and soluble materials do not sediment)
fractionation
the process of separating the proteins or other components of a complex molecular mixture
into fractions based on differences in properties such as solubility, net charge, molecular
weight, or function
dialysis
removal of small molecules from a solution of a macromolecule by their diffusion through a
semi permeable membrane into a suitably buffered solution
column chromatography
- a technique where a porous solid material with appropriate chemical properties (stationary
phase) is held in a column and a buffering solution (mobile phase) migrates through it.
- takes advantage of differences in protein charge, size, binding affinity, and other properties.
ion-exchange chromatography
a process for separating complex mixtures of ionic compounds by many repeated
partitionings between a flowing phase and a stationary phase consisting of a polymeric resin
that contains fixed charged groups
on what basis are proteins separated using ion-exchange chromatography?
differences in the sign and magnitude of the net electric charge of proteins at a given pH
What is the overall charge on a protein when the pH < pI? pH = pI? pH > pI?
