BIOCHEM 4300 EXAM 4 QUESTIONS WITH CORRECT
DETAILED ANSWERS 100% VERIFIED
What is the mean free path? - ANSWER average distance traveled between collisions
What is diffusion driven by? - ANSWER chemical potential
What is flux (flow) defined as? - ANSWER amount of solute diffusing across a unit area
per unit time
What does Fick's first law state? - ANSWER the rate of diffusion is proportional to
concentration gradient
What conditions do Fick's second law apply to? - ANSWER non-steady conditions
What are two reasons why the rate of diffusion in solution increases with temperature? -
ANSWER a) solute has greater KE at higher temperature
b) solvent viscosity decreases with temperature
Why can't Na+ pass through the selectivity filter of potassium channel despite being
smaller than K+? - ANSWER dehydrated K+ can be stabilized by carbonyl group of
protein residues in the selectivity filter to mimic the hydrating state of K+
Na+ is too small to be stabilized by the carbonyl groups to compensate for the Gibbs
energy of dehydration
On a 2d gel, which protein is the smallest? - ANSWER most vertically close to the bottom
,On a 2d gel, which protein has the highest PI? - ANSWER one farthest to the right
In what type of sedimentation experiments is the sample layered on top of a density
gradient? - ANSWER zonal
In what type of sedimentation experiments is the sample initially uniformly distributed
throughout the sample cell? - ANSWER boundary
What are the two classes of boundary sedimentation experiment? - ANSWER velocity
sedimentation
equilibrium sedimentation
Net solute transport is characteristic of which class of boundary experiment? - ANSWER
velocity sedimentation
When a solute molecule is sedimented in a centrifuge, the centrifugal force on the
molecule is opposed by which forces? - ANSWER buoyancy force
frictional force
What governs the magnitude of the sedimentation coefficient? - ANSWER particle mass
surface area
How does observed sedimentation coefficient change with solvent density? - ANSWER
decreases with solvent density
How does observed sedimentation coefficient change with temperature? - ANSWER
increases with temperature
What two factors strongly influence the concentration-dependence of the sedimentation
coefficient? - ANSWER size of molecule
, shape of molecule
What are three advantages of using zonal sedimentation relative to boundary
experiments? - ANSWER improved resolution of sample components
greater flexibility for detecting components (not limited to optical detection. can employ
enzymatic activity, radioisotracers, bioassy
modest equilibrium requirements. employs a standard preparative ultracentrifuge
What is the primary disadvantage of zonal velocity experiments? - ANSWER a density
gradient (e.g. sucrose, glycerol) is required to prevent convection
How to tell if a viral protein is packaged into a particular virion? - ANSWER if upon
centrifugation the proteins are found in same gel as proteins that are known to be
packaged in the virion
What is plotted along the x-axis of a mass spectrum? - ANSWER mass to charge ratio
How does mass affect a protein going through an electric or magnetic field in a vacuum
chamber? - ANSWER slows the acceleration caused by the charge
What are the two most important forms of mass spec used to detect proteins? -
ANSWER MALDI-TOF
electrospray mass spectrometry
What does MALDI-TOF stand for? - ANSWER Matrix-Associated Laser
Desorption-ionization time of flight
Which proton in protein backbone can exchange with solvent water? - ANSWER amide
proton
DETAILED ANSWERS 100% VERIFIED
What is the mean free path? - ANSWER average distance traveled between collisions
What is diffusion driven by? - ANSWER chemical potential
What is flux (flow) defined as? - ANSWER amount of solute diffusing across a unit area
per unit time
What does Fick's first law state? - ANSWER the rate of diffusion is proportional to
concentration gradient
What conditions do Fick's second law apply to? - ANSWER non-steady conditions
What are two reasons why the rate of diffusion in solution increases with temperature? -
ANSWER a) solute has greater KE at higher temperature
b) solvent viscosity decreases with temperature
Why can't Na+ pass through the selectivity filter of potassium channel despite being
smaller than K+? - ANSWER dehydrated K+ can be stabilized by carbonyl group of
protein residues in the selectivity filter to mimic the hydrating state of K+
Na+ is too small to be stabilized by the carbonyl groups to compensate for the Gibbs
energy of dehydration
On a 2d gel, which protein is the smallest? - ANSWER most vertically close to the bottom
,On a 2d gel, which protein has the highest PI? - ANSWER one farthest to the right
In what type of sedimentation experiments is the sample layered on top of a density
gradient? - ANSWER zonal
In what type of sedimentation experiments is the sample initially uniformly distributed
throughout the sample cell? - ANSWER boundary
What are the two classes of boundary sedimentation experiment? - ANSWER velocity
sedimentation
equilibrium sedimentation
Net solute transport is characteristic of which class of boundary experiment? - ANSWER
velocity sedimentation
When a solute molecule is sedimented in a centrifuge, the centrifugal force on the
molecule is opposed by which forces? - ANSWER buoyancy force
frictional force
What governs the magnitude of the sedimentation coefficient? - ANSWER particle mass
surface area
How does observed sedimentation coefficient change with solvent density? - ANSWER
decreases with solvent density
How does observed sedimentation coefficient change with temperature? - ANSWER
increases with temperature
What two factors strongly influence the concentration-dependence of the sedimentation
coefficient? - ANSWER size of molecule
, shape of molecule
What are three advantages of using zonal sedimentation relative to boundary
experiments? - ANSWER improved resolution of sample components
greater flexibility for detecting components (not limited to optical detection. can employ
enzymatic activity, radioisotracers, bioassy
modest equilibrium requirements. employs a standard preparative ultracentrifuge
What is the primary disadvantage of zonal velocity experiments? - ANSWER a density
gradient (e.g. sucrose, glycerol) is required to prevent convection
How to tell if a viral protein is packaged into a particular virion? - ANSWER if upon
centrifugation the proteins are found in same gel as proteins that are known to be
packaged in the virion
What is plotted along the x-axis of a mass spectrum? - ANSWER mass to charge ratio
How does mass affect a protein going through an electric or magnetic field in a vacuum
chamber? - ANSWER slows the acceleration caused by the charge
What are the two most important forms of mass spec used to detect proteins? -
ANSWER MALDI-TOF
electrospray mass spectrometry
What does MALDI-TOF stand for? - ANSWER Matrix-Associated Laser
Desorption-ionization time of flight
Which proton in protein backbone can exchange with solvent water? - ANSWER amide
proton
