Chapter 19 - Oxidative Phosphorylation
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University of Toronto, Toronto School of Theology *
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Course
BLG144
Subject
Biology
Date
Dec 6, 2023
Type
Pages
8
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Chapter
19a
Oxidative
Phosphorylation
and
Photophosphorylation
Multiple
Choice
Questions
1.
Electron-transfer
reactions
in
mitochondria
Page:
707
Difficulty:
1
Ans:
E
Almost
all
of
the
oxygen
(O,)
one
consumes
in
breathing
is
converted
to:
A)
acetyl-CoA.
B)
carbon
dioxide
(CO,).
C)
carbon
monoxide
and
then
to
carbon
dioxide.
D)
none
of
the
above.
E)
water.
2.
Electron-transfer
reactions
in
mitochondria
Pages:
712-713
Difficulty:
2
Ans:
B
Antimycin
A
blocks
electron
transfer
between
cytochromes
b
and
c1.
If
intact
mitochondria
were
incubated
with
antimycin
A,
excess
NADH,
and
an
adequate
supply
of
O, which
of
the
following
would
be
found
in
the
oxidized
state?
A)
Coenzyme
Q
B)
Cytochrome
a3
C)
Cytochrome
b
D)
Cytochrome
e
E)
Cytochrome
f
3.
Electron-transfer
reactions
in
mitochondria
Pages:
715-716
Difficulty:
2
Ans:
A
In
the
reoxidation
of
QH,
by purified
ubiquinone-cytochrome
c
reductase
(Complex
III)
from
heart
muscle,
the
overall
stoichiometry
of
the
reaction
requires
2
mol
of
cytochrome
c
per
mole
of
QH,
because:
A)
cytochrome
c
is
a
one-electron
acceptor,
whereas
QH
is
a
two-electron
donor.
B)
cytochrome
c
is
a
two-electron
acceptor,
whereas
QHs,
is
a
one-electron
donor.
C)
cytochrome
c
is
water
soluble and
operates
between
the
inner
and
outer
mitochondrial
membranes
D)
heart
muscle
has
a
high
rate
of
oxidative
metabolism,
and
therefore
requires
twice
as
much
cytochrome
c
as
QH,
for
electron
transfer
to
proceed
normally.
E)
two
molecules
of
cytochrome
¢
must
first
combine
physically
before
they
are
catalytically
active.
4.
ATP
synthesis
Page:
712
Difficulty:
3
Ans:
A
If
electron
transfer
in
tightly
coupled
mitochondria
is
blocked
(with
antimycin
A)
between
cytochrome
b
and
cytochrome
c1,
then:
A)
B)
o]
D)
E)
all
ATP
synthesis
will
stop.
ATP
synthesis
will
continue,
but
the
P/O
ratio
will
drop
to
one.
electron
transfer
from
NADH
will
cease,
but
O,
uptake
will
continue.
electron
transfer
from
succinate
to
O,
will
continue
unabated.
energy
diverted
from
the
cytochromes
will
be
used
to
make
ATP,
and
the
P/O
ratio
will
rise.
ATP
synthesis
Pages:
722-723
Difficulty:
2
Ans:
A
‘Which
of
the
following
statements
about
the
chemiosmotic
theory
is
correct?
A)
B)
®)
D)
E)
Electron
transfer
in
mitochondria
is
accompanied
by
an
asymmetric
release
of
protons
on
one
side
of
the
inner
mitochondrial
membrane.
It
predicts
that
oxidative
phosphorylation
can
occur
even
in
the
absence
of
an
intact
inner
mitochondrial
membrance.
The
effect
of
uncoupling
reagents
is
a
consequence
of
their
ability
to
carry
electrons
through
membranes.
The
membrane
ATP
synthase
has no
significant
role
in
the
chemiosmotic
theory.
All
of
the
above
are
correct.
ATP
synthesis
Pages:
722-723
Difficulty:1
Ans:
E
‘Which
of
the
following
statements
about
the
chemiosmotic
theory
is
false?
A)
B)
0
D)
E)
Electron
transfer
in
mitochondria
is
accompanied
by
an
asymmetric
release
of
protons
on
one
side
of
the
inner
mitochondrial
membrane.
Energy
is
conserved
as
a
transmembrane
pH
gradient.
Oxidative
phosphorylation
cannot
occur
in
membrane-free
preparations.
The
effect
of
uncoupling
reagents
is
a
consequence
of
their
ability
to
carry
protons
through
membranes.
The
membrane
ATPase,
which
plays
an
important
role
in
other
hypotheses
for
energy
coupling,
has
no
significant
role
in
the
chemiosmotic
theory.
ATP
synthesis
Pages:
722-723
Difficulty:
3
Ans:
A
‘Upon
the
addition
of
an
uncoupler
(collapses
the
trans-membrane
proton
gradient)
to
a
suspension
of
mitochondria
carrying
out
oxidative
phosphorylation
linked
to
the
oxidation
of
malate,
all
of
the
following
occur
except:
A)
B)
oxygen
consumption
decreases.
oxygen
consumption
increases.
o)
D)
E)
the
P/O
ratio
drops
from
a
value
of
approximately
2.5
to
0.
the
proton
gradient
dissipates.
the
rate
of
transport
of
electrons
from
NADH
to
O,
becomes
maximal.
8.
ATP
synthesis
Page:
724
Difficulty:
1
Ans:
C
Uncoupling
of
mitochondrial
oxidative
phosphorylation:
A)
B)
o]
D)
E)
allows
continued
mitochondrial
ATP
formation,
but
halts
O,
consumption.
halts
all
mitochondrial
metabolism.
halts
mitochondrial
ATP
formation,
but
allows
continued
O,
consumption.
slows
down
the
citric
acid
cycle.
slows
the
conversion
of
glucose
to
pyruvate
by
glycolysis.
9.
ATP
synthesis
Page:
724
Difficulty:
2
Ans:
A
Oligomycin
inhibits
ATP
synthase
while
DNP
is
an
uncoupler.
Therefore,
DNP
will:
A)
B)
Q)
D)
E)
allow
electron
transfer
in
the
presence
of
oligomycin.
allow
oxidative
phosphorylation
in
the
presence
of
oligomycin.
block
electron
transfer
in
the
presence
of
oligomycin.
diminish
O,
consumption
in
the
presence
of
oligomycin
do
none
of
the
above.
10.
ATP
synthesis
Page:
724
Difficulty:
1
Ans:
D
‘Which
of
the
following
statements
about
energy
conservation
in
the
mitochondrion
is
false?
A)
B)
9
D)
E)
Drug
that
inhibits
the
ATP
synthase
will
also
inhibit
the
flow
of
electrons
down
the
chain
of
carriers.
For
oxidative
phosphorylation
to
occur,
it
is
essential
to
have
a
closed
membranous
structure
with
an
inside
and
an
outside.
The
yield
of
ATP
per
mole
of
oxidizable
substrate
depends
on
the
substrate.
Uncouplers
(such
as
dinitrophenol)
have
exactly
the
same
effect
on
electron
transfer
as
inhibitors
such
as
cyanide;
both
block
further
electron
transfer
to
oxygen.
Uncouplers
“short
circuit”
the
proton
gradient,
thereby
dissipating
the
proton
motive
force
as
heat.
11.
ATP
synthesis
Page:
725
Difficulty:
2
Ans:
E
‘Which
of
the
following
is
correct
concerning
the
mitochondrial
ATP
synthase?
A)
B)
It
can
synthesize
ATP
after
it
is
extracted
from
broken
mitochondria.
It
catalyzes
the
formation
of
ATP
even
though
the
reaction
has
a
large
positive
deltaG".
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