BSCI 1510 FINAL EXAM
BSCI 1510 FINAL EXAM QUESTIONS AND ANSWERS GRADED A+
ways to increase membrane fluidity ANS >> make membrane phospholipids with
shorter fatty acid tails or tails with more double bonds (less saturated) or insert
more cholesterol into the membrane so that it is more fluid at lower
temperatures. High membrane fluidity/flexibility is required for membrane
budding during the formation of spherical transport vesicles for endocytosis.
final destination of a protein with two 20 aa hydrophobic alpha helices, one right
at the N terminus and the other halfway along the protein length ANS >> to be a
single-pass transmembrane protein in the plasma membrane. The N terminal
alpha helix is the signal peptide that directs endoplasmic reticulum translocation
and is cleaved afterward. The internal alpha helix gets arrested in the transposon
and is maintained as the membrane spanning domain. Without other signals,
vesicle transport delivers it to the plasma membrane
energy barrier overcome by Snares ANS >> Transmembrane V- and T-Snares wind
around each other in an energetically favourable (-DG) interaction that overcomes
the hydrophilic/hydrophobic barrier energy cost (+DG) of membrane fusion. The
coiled-coil conformation of the assembled SNARE complex must be a very low
energy state, requiring energy input to unwind the V- and T-Snares prior to the
next fusion event.
,BSCI 1510 FINAL EXAM
2 oxygen-involving processes that evolved in bacteria ANS >> photosynthesis and
aerobic metabolic pathways (oxidative respiration). Both were acquired by
eukaryotic cells via an endosymbiotic relationship. First mitochondria in all
eukaryotes ~2 bay and then chloroplasts ~1.5 bay separating plants from animals.
what makes a covalent bond polar, and how does this explain protein beta sheet
stability? ANS >> Electrons spend more time at the more electronegative atom
(generating partial charge separation) if their electronegativities differ
significantly. A protein beta sheet is stabilized by hydrogen bonds between the
polar N-H and C=O of peptide bonds in adjacent strands.
osmotic consequence if [ATP] and [ADP] are at equilibrium ANS >> no capacity to
perform work! so cells need much higher [ATP]. Na+/K+ pump is an ATPase that
maintains the outside high [Na+] required to balance osmosis across the plasma
membrane. When ATP and ADP are at equilibrium, the ATPase pump can't work,
the gradient degrades, water rushes in, and the cell bursts.
freeze-fracture TEM in understanding synapse function ANS >> (splitting the
membrane between the two phospholipid leaflets so that the interior of the
membrane can be viewed with high resolution electron microscopy. Revealed that
vesicle fusion occurs within milliseconds of an action potential, immediately
adjacent to voltage-gated Ca2+ channels, linking Ca2+ influx with transmitter
secretion.
energy cost in trafficking a protein with an N-terminus amphipathic alpha helix to
its final destination within the cell ANS >> The protein must be unfolded by a
systolic HSP70 chaperone, requiring ATP hydrolysis by this ATPase, then refolded
by a mitochondrial HSP70 chaperone, again requiring ATP hydrolysis by this
second ATPase. The transport process across the mitochondrial inner membrane
requires an electrical potential.
, BSCI 1510 FINAL EXAM
overall energetics of a reaction with K(eq)=0.001 ANS >> positive DG, meaning
that it is energetically unfavourable (endergonic/endothermic) and will not
proceed spontaneously without energy input. An enzyme would increase the
reaction rate by lowering the activation energy, but would not alter the DG
energetics. Increasing the K(m) of the enzyme would make it a less effective
catalyst and require a higher substrate concentration to perform its job.
how does an ion channel allow passage of a large cation while excluding a smaller
cation ANS >> In water, cations are stabilized by partially negative oxygen atoms,
creating a bulky water of hydration sphere that is too large to pass. In the ion
channel selectivity filter, carbonyl (C=O) groups on aa residues replace this
function, temporarily displacing the hydration sphere. These groups are placed far
enough apart to stabilize the larger cation but not the smaller.
compare/contrast ATP and NADH ANS >> both molecules contain adenine, ribose,
and phosphate groups, but ATP carries energy in high-energy covalent bonds
(phosphate transfer potential) while NADH carries energy in high-energy electrons
(negative redox potential)
protein that makes ATP ANS >> ATP synthase uses proton motive force to make
ATP. The pH (H+ concentration) difference and voltage (charge separation)
potential together produce the free energy released (-DG) when protons flow
down their electrochemical gradient through ATP synthase. It acts as a rotational
catalyst to do the work (+DG) of making a covalent bond between ADP and Pi.
structure of intermediate filaments ANS >> two alpha helical monomer proteins
form a coiled-coil dimer; two dimers are offset and face opposite directions to
form an anti-parallel staggered tetramer; and 8 tetramers combine to form a
single intermediate filament
BSCI 1510 FINAL EXAM QUESTIONS AND ANSWERS GRADED A+
ways to increase membrane fluidity ANS >> make membrane phospholipids with
shorter fatty acid tails or tails with more double bonds (less saturated) or insert
more cholesterol into the membrane so that it is more fluid at lower
temperatures. High membrane fluidity/flexibility is required for membrane
budding during the formation of spherical transport vesicles for endocytosis.
final destination of a protein with two 20 aa hydrophobic alpha helices, one right
at the N terminus and the other halfway along the protein length ANS >> to be a
single-pass transmembrane protein in the plasma membrane. The N terminal
alpha helix is the signal peptide that directs endoplasmic reticulum translocation
and is cleaved afterward. The internal alpha helix gets arrested in the transposon
and is maintained as the membrane spanning domain. Without other signals,
vesicle transport delivers it to the plasma membrane
energy barrier overcome by Snares ANS >> Transmembrane V- and T-Snares wind
around each other in an energetically favourable (-DG) interaction that overcomes
the hydrophilic/hydrophobic barrier energy cost (+DG) of membrane fusion. The
coiled-coil conformation of the assembled SNARE complex must be a very low
energy state, requiring energy input to unwind the V- and T-Snares prior to the
next fusion event.
,BSCI 1510 FINAL EXAM
2 oxygen-involving processes that evolved in bacteria ANS >> photosynthesis and
aerobic metabolic pathways (oxidative respiration). Both were acquired by
eukaryotic cells via an endosymbiotic relationship. First mitochondria in all
eukaryotes ~2 bay and then chloroplasts ~1.5 bay separating plants from animals.
what makes a covalent bond polar, and how does this explain protein beta sheet
stability? ANS >> Electrons spend more time at the more electronegative atom
(generating partial charge separation) if their electronegativities differ
significantly. A protein beta sheet is stabilized by hydrogen bonds between the
polar N-H and C=O of peptide bonds in adjacent strands.
osmotic consequence if [ATP] and [ADP] are at equilibrium ANS >> no capacity to
perform work! so cells need much higher [ATP]. Na+/K+ pump is an ATPase that
maintains the outside high [Na+] required to balance osmosis across the plasma
membrane. When ATP and ADP are at equilibrium, the ATPase pump can't work,
the gradient degrades, water rushes in, and the cell bursts.
freeze-fracture TEM in understanding synapse function ANS >> (splitting the
membrane between the two phospholipid leaflets so that the interior of the
membrane can be viewed with high resolution electron microscopy. Revealed that
vesicle fusion occurs within milliseconds of an action potential, immediately
adjacent to voltage-gated Ca2+ channels, linking Ca2+ influx with transmitter
secretion.
energy cost in trafficking a protein with an N-terminus amphipathic alpha helix to
its final destination within the cell ANS >> The protein must be unfolded by a
systolic HSP70 chaperone, requiring ATP hydrolysis by this ATPase, then refolded
by a mitochondrial HSP70 chaperone, again requiring ATP hydrolysis by this
second ATPase. The transport process across the mitochondrial inner membrane
requires an electrical potential.
, BSCI 1510 FINAL EXAM
overall energetics of a reaction with K(eq)=0.001 ANS >> positive DG, meaning
that it is energetically unfavourable (endergonic/endothermic) and will not
proceed spontaneously without energy input. An enzyme would increase the
reaction rate by lowering the activation energy, but would not alter the DG
energetics. Increasing the K(m) of the enzyme would make it a less effective
catalyst and require a higher substrate concentration to perform its job.
how does an ion channel allow passage of a large cation while excluding a smaller
cation ANS >> In water, cations are stabilized by partially negative oxygen atoms,
creating a bulky water of hydration sphere that is too large to pass. In the ion
channel selectivity filter, carbonyl (C=O) groups on aa residues replace this
function, temporarily displacing the hydration sphere. These groups are placed far
enough apart to stabilize the larger cation but not the smaller.
compare/contrast ATP and NADH ANS >> both molecules contain adenine, ribose,
and phosphate groups, but ATP carries energy in high-energy covalent bonds
(phosphate transfer potential) while NADH carries energy in high-energy electrons
(negative redox potential)
protein that makes ATP ANS >> ATP synthase uses proton motive force to make
ATP. The pH (H+ concentration) difference and voltage (charge separation)
potential together produce the free energy released (-DG) when protons flow
down their electrochemical gradient through ATP synthase. It acts as a rotational
catalyst to do the work (+DG) of making a covalent bond between ADP and Pi.
structure of intermediate filaments ANS >> two alpha helical monomer proteins
form a coiled-coil dimer; two dimers are offset and face opposite directions to
form an anti-parallel staggered tetramer; and 8 tetramers combine to form a
single intermediate filament
