BCH210 EXAM QUESTIONS
WITH COMPLETE SOLUTIONS
electron transport chain - Answer- -electrons passed from carrier to carrier
-electron transfer potential of carriers is measured by standard reduction potential, E'0
-good reducing agents give up electrons easily and have -E'0 values (or smaller +)
-strong oxidizing agents have a greater affinity for electrons and have +E'0 values
-passage of electrons results in free energy change that establishes a proton gradient
for ATP synthesis
ETC prosthetic groups - Answer- FMN (complex I) groups
FAD (complex II) groups
iron-sulfur complexes (complex I, II, III)
coenzyme Q (ubiquinone) (from complex I & II to III)
cytochromes (complex III & IV)
protein bound copper (complex IV)
coenzyme Q - Answer- carries 2 e-
eletron transport chain order - Answer- 1. NADH oxidoreductase (complex I) -> 4
protons
2. succinate Q reductase (complex II)
3. Q-cytochrome c oxidoreductase (complex III) -> 4 protons
4. cytochrome c oxidase (complex IV) -> 2 protons
what is complex I in the ETC? how many protons are pumped here? - Answer- NADH
oxidoreductase
4
what is complex II in the ETC?how many protons are pumped here? - Answer-
succinate Q reductase
0
what is complex III in the ETC?how many protons are pumped here? - Answer- Q-
cytochrome c oxidoreductase
4
what is complex IV in the ETC?how many protons are pumped here? - Answer-
cytochrome c oxidase
2
O2 in ETC - Answer- final electron acceptor
,electron transfer potential calculation - Answer- acceptor - donor
(bigger number - smaller)
in the ETC ΔE'0 = 1.14 V
electron transport and ATP synthase - Answer- -for every 4H+, 1 ATP is made
-since NADH donates it's e- to complex I (4 + 4 + 2 = 10 H+)
-since NADH cytosol and FADH2 donates their e- to complex II ( 4+ 2 = 6 H+)
ETC inhibitors - Answer- -rotenone and amytal inhibit e- flow from FeS to CoQ in
complex I
-antimycin A blocks complex III
-cyanide, azide and CO inhibit complex IV
CO and the ETC - Answer- CO blocks O2 formation, blocks complex IV
if amytal blocks complex I - Answer- add succinate to make FADH2 and bypass
complex I, add at complex II, less ATP made
Mitchell's chemiosmotic hypothesis - Answer- The potential energy associated with the
proton gradient across the inner mitochondrial membrane provides the driving force for
the synthesis of ATP
ATP synthase is.... (Mitchell) - Answer- membrane-bound
reversible
and dependent on the proton gradient
Mitchell discoveries - Answer- -stress promotes leaky mitochondrial membranes
-ATP synthase needs intact membranes
-uncouplers of oxidative phosphorylation have diff structures and disrupt the proton
gradient
-swelling or shrinking of mitochondria can also affect ATP synthesis
uncouplers disrupt the H+ gradient - Answer- -bind protons, hydrophobic groups bring
H+ across membrane instead of protons going through ATP synthase
1. DNP
2. salicylate
3. FCCP
oxidative phosphorylation - Answer- -the proton-motive force established by the ETC is
the driving force behind ATP synthesis
-uncouplers can dissipate the proton gradient, preventing ATP synthesis but allows e-
transport to occur
-ATP synthase can be inhibited by oligomycin
-ATP synthesis can occur using protons not supplied by ETC (mitochondria in low pH
buffer)
,- ATP hydrolysis can result in H+ pumping in reverse direction
mitochondrial experiments - Answer- show that there is a lag in production to build up a
proton gradient and then eventually O2 consumed and ATP synthesized plateaus over
time as e- donors or H+ runs out
ATP synthase - Answer- large protein that uses energy from H+ ions to bind ADP and a
phosphate group together to produce ATP (or reverse)
-has an F1 and F0 unit
-F0 unit is the integral membrane protein unit that anchors the enzyme in the inner
mitochondrial membrane
-F1 is the peripheral protein unti that caries out the catalytic synthesis of ATP in the
matrix
-conformational changes in the F1β subunits are responsible for ATP synthesis
-ATP is exported out of the matrix for use in the rest of the cell by ATP/ADP translocase
ATP synthase
F0 complex - Answer- the integral membrane protein unit that anchors the enzyme in
the inner mitochondrial membrane
-consists of: ab2c10-15dh
-c is where oligomycin binds to prevent H+ binding
-a is where the H+ binds
ATP synthase
F1 complex - Answer- the peripheral protein unti that caries out the catalytic synthesis
of ATP in the matrix
-consists of: α3β3γδε
-β subunits are responsible for ATP synthesis
-γ is the rotor shaft that contacts β subunits and tells them to turn from loose state to
tight state to form ATP and release it into solution
boyer's binding change mechanism - Answer- each β subunit undergoes a
conformational change between 3 states (staggered so any subunit can be at each
state)
-*O*pen or *E*mpty/*E*xit
-*L*oose with A*DP* and Pi bound
-*T*ight with A*TP* bound
-γ is the rotor shaft that contacts β subunits and tells them to turn from loose state to
tight state to form ATP and release it into solution
ATP synthase is reversible - Answer- ATP hydrolysis can be used to drive the reverse
mechanism
can also drive proton transport via ATP hydrolysis
ATP synthase process - Answer- -β subunit in F1 is responsible for ATP synthesis
, - protons flow through the c ring, inducing a conformation change in β subunits via γ
subunit rotation
-3 H+ are pumped per ATP molecule synthesized (depends on #c 10-15)
-1 H+ needed to ATP export out of mitochondria
- therefore ~4H+ required/ATP
4th H+ - Answer- needed for ATP export
ATP has -4 charge, ADP has -3 charge and Pi has -2 so extra proton to maintain the
charge neutrality to -4
P/O ratio - Answer- the number of moles of Pi consumed in phosphorylation to the
number of moles of oxygen atoms consumed in oxidation
-NADH = 2.5ATP
-NADH cyt or FADH2 = 1.5 ATP
(can't actually make 0.5ATP, round down)
NADHcyt P/O ratio is exception
glycerophosphate shuttle - Answer- Dihydroxyacetone phosphate cycles back and forth
from glycerol 3-phosphate. Going to DHAP it consumes NADH. Going to GAP it
produces FADH2.
-thi is the way to transfer the pair of e- from NADH in the cytosol to FADH2
water formation in oxidative phosphorylation - Answer- 2.5 H2O generated w/ 2.5 ATP
formation from NADH
1.5 H2O generated w/ 1.5 ATP formation from FADH2 or NADHcyt
+1 H2O formed in last step of electron transfer at complex IV so:
NADH = 3.5 H2O
FADH2/NADHcyt = 2.5 H2O
lactate dehydrogenase - Answer- enzyme responsible for converting pyruvate into
lactate by using NADH when there is no oxygen (aka oxidative phosphorylation cannot
occur), excess pyruvate is converted to lactate to replenish NAD+ so that glycolysis can
continue to produce a little ATP
anaerobic metabolism - Answer- occurs in the absence of oxygen
glycolysis is the only means of generating ATP
lactate dehydrogenase depletes NADH levels so no ATP is made from NADHcyt by
oxidative phosphorylation
NAD+ replenished for glycolysis
glucose + 2ADP + 2Pi --> 2 lactate + 2ATP + 2H2O
alcohol fermentation and NADH - Answer- in yeast, two consecutive reactions produce
CO2 and ethanol, but also replenish NAD+ for glycolysis
pyruvate --> acetyl aldehyde --> ethanol
using pyruvate decarboxylase and alcohol dehydrogenase
WITH COMPLETE SOLUTIONS
electron transport chain - Answer- -electrons passed from carrier to carrier
-electron transfer potential of carriers is measured by standard reduction potential, E'0
-good reducing agents give up electrons easily and have -E'0 values (or smaller +)
-strong oxidizing agents have a greater affinity for electrons and have +E'0 values
-passage of electrons results in free energy change that establishes a proton gradient
for ATP synthesis
ETC prosthetic groups - Answer- FMN (complex I) groups
FAD (complex II) groups
iron-sulfur complexes (complex I, II, III)
coenzyme Q (ubiquinone) (from complex I & II to III)
cytochromes (complex III & IV)
protein bound copper (complex IV)
coenzyme Q - Answer- carries 2 e-
eletron transport chain order - Answer- 1. NADH oxidoreductase (complex I) -> 4
protons
2. succinate Q reductase (complex II)
3. Q-cytochrome c oxidoreductase (complex III) -> 4 protons
4. cytochrome c oxidase (complex IV) -> 2 protons
what is complex I in the ETC? how many protons are pumped here? - Answer- NADH
oxidoreductase
4
what is complex II in the ETC?how many protons are pumped here? - Answer-
succinate Q reductase
0
what is complex III in the ETC?how many protons are pumped here? - Answer- Q-
cytochrome c oxidoreductase
4
what is complex IV in the ETC?how many protons are pumped here? - Answer-
cytochrome c oxidase
2
O2 in ETC - Answer- final electron acceptor
,electron transfer potential calculation - Answer- acceptor - donor
(bigger number - smaller)
in the ETC ΔE'0 = 1.14 V
electron transport and ATP synthase - Answer- -for every 4H+, 1 ATP is made
-since NADH donates it's e- to complex I (4 + 4 + 2 = 10 H+)
-since NADH cytosol and FADH2 donates their e- to complex II ( 4+ 2 = 6 H+)
ETC inhibitors - Answer- -rotenone and amytal inhibit e- flow from FeS to CoQ in
complex I
-antimycin A blocks complex III
-cyanide, azide and CO inhibit complex IV
CO and the ETC - Answer- CO blocks O2 formation, blocks complex IV
if amytal blocks complex I - Answer- add succinate to make FADH2 and bypass
complex I, add at complex II, less ATP made
Mitchell's chemiosmotic hypothesis - Answer- The potential energy associated with the
proton gradient across the inner mitochondrial membrane provides the driving force for
the synthesis of ATP
ATP synthase is.... (Mitchell) - Answer- membrane-bound
reversible
and dependent on the proton gradient
Mitchell discoveries - Answer- -stress promotes leaky mitochondrial membranes
-ATP synthase needs intact membranes
-uncouplers of oxidative phosphorylation have diff structures and disrupt the proton
gradient
-swelling or shrinking of mitochondria can also affect ATP synthesis
uncouplers disrupt the H+ gradient - Answer- -bind protons, hydrophobic groups bring
H+ across membrane instead of protons going through ATP synthase
1. DNP
2. salicylate
3. FCCP
oxidative phosphorylation - Answer- -the proton-motive force established by the ETC is
the driving force behind ATP synthesis
-uncouplers can dissipate the proton gradient, preventing ATP synthesis but allows e-
transport to occur
-ATP synthase can be inhibited by oligomycin
-ATP synthesis can occur using protons not supplied by ETC (mitochondria in low pH
buffer)
,- ATP hydrolysis can result in H+ pumping in reverse direction
mitochondrial experiments - Answer- show that there is a lag in production to build up a
proton gradient and then eventually O2 consumed and ATP synthesized plateaus over
time as e- donors or H+ runs out
ATP synthase - Answer- large protein that uses energy from H+ ions to bind ADP and a
phosphate group together to produce ATP (or reverse)
-has an F1 and F0 unit
-F0 unit is the integral membrane protein unit that anchors the enzyme in the inner
mitochondrial membrane
-F1 is the peripheral protein unti that caries out the catalytic synthesis of ATP in the
matrix
-conformational changes in the F1β subunits are responsible for ATP synthesis
-ATP is exported out of the matrix for use in the rest of the cell by ATP/ADP translocase
ATP synthase
F0 complex - Answer- the integral membrane protein unit that anchors the enzyme in
the inner mitochondrial membrane
-consists of: ab2c10-15dh
-c is where oligomycin binds to prevent H+ binding
-a is where the H+ binds
ATP synthase
F1 complex - Answer- the peripheral protein unti that caries out the catalytic synthesis
of ATP in the matrix
-consists of: α3β3γδε
-β subunits are responsible for ATP synthesis
-γ is the rotor shaft that contacts β subunits and tells them to turn from loose state to
tight state to form ATP and release it into solution
boyer's binding change mechanism - Answer- each β subunit undergoes a
conformational change between 3 states (staggered so any subunit can be at each
state)
-*O*pen or *E*mpty/*E*xit
-*L*oose with A*DP* and Pi bound
-*T*ight with A*TP* bound
-γ is the rotor shaft that contacts β subunits and tells them to turn from loose state to
tight state to form ATP and release it into solution
ATP synthase is reversible - Answer- ATP hydrolysis can be used to drive the reverse
mechanism
can also drive proton transport via ATP hydrolysis
ATP synthase process - Answer- -β subunit in F1 is responsible for ATP synthesis
, - protons flow through the c ring, inducing a conformation change in β subunits via γ
subunit rotation
-3 H+ are pumped per ATP molecule synthesized (depends on #c 10-15)
-1 H+ needed to ATP export out of mitochondria
- therefore ~4H+ required/ATP
4th H+ - Answer- needed for ATP export
ATP has -4 charge, ADP has -3 charge and Pi has -2 so extra proton to maintain the
charge neutrality to -4
P/O ratio - Answer- the number of moles of Pi consumed in phosphorylation to the
number of moles of oxygen atoms consumed in oxidation
-NADH = 2.5ATP
-NADH cyt or FADH2 = 1.5 ATP
(can't actually make 0.5ATP, round down)
NADHcyt P/O ratio is exception
glycerophosphate shuttle - Answer- Dihydroxyacetone phosphate cycles back and forth
from glycerol 3-phosphate. Going to DHAP it consumes NADH. Going to GAP it
produces FADH2.
-thi is the way to transfer the pair of e- from NADH in the cytosol to FADH2
water formation in oxidative phosphorylation - Answer- 2.5 H2O generated w/ 2.5 ATP
formation from NADH
1.5 H2O generated w/ 1.5 ATP formation from FADH2 or NADHcyt
+1 H2O formed in last step of electron transfer at complex IV so:
NADH = 3.5 H2O
FADH2/NADHcyt = 2.5 H2O
lactate dehydrogenase - Answer- enzyme responsible for converting pyruvate into
lactate by using NADH when there is no oxygen (aka oxidative phosphorylation cannot
occur), excess pyruvate is converted to lactate to replenish NAD+ so that glycolysis can
continue to produce a little ATP
anaerobic metabolism - Answer- occurs in the absence of oxygen
glycolysis is the only means of generating ATP
lactate dehydrogenase depletes NADH levels so no ATP is made from NADHcyt by
oxidative phosphorylation
NAD+ replenished for glycolysis
glucose + 2ADP + 2Pi --> 2 lactate + 2ATP + 2H2O
alcohol fermentation and NADH - Answer- in yeast, two consecutive reactions produce
CO2 and ethanol, but also replenish NAD+ for glycolysis
pyruvate --> acetyl aldehyde --> ethanol
using pyruvate decarboxylase and alcohol dehydrogenase
