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These processes account
for most of the ATP generated in living cells
transport and oxidative phosphorylation
what is the end product of lipid, carbohydrate, and protein
AcetylCoA is used in the TCA cycle to generate reduced nucleotides
—NADH and FADH2.
Those reduced nucleotides then donate their high energy electron into the electron transport pathways, which generates a proton gradient across the inner mitochondrial membrane.
the proton gradient is used by
(?) to drive the synthesis of ATP from ADP and Pi.
In eukaryotic cells, the electron transport and oxidative phosphorylation systems are located in
Oxidative phosphorylation is a composite of two biochemical
electron transport driven proton pumping and proton
driven ATP synthesis.
These two processes work in tandem to produce ATP from reduced nucleotides such as NADH and FADH2.
ATP synthase uses (?) to drive the synthesis of ATP from ADP and Pi.
Electron transport is a process in which the transport of protons out of the mitochondrial matrix is energized by (?) within the mitochondrial inner membrane.
the flow of electrons
through various protein complexes
Electron transport leads to the formation of a proton
gradient with high proton concentration in (?) and low proton concentration (?)
The ATP synthase enzyme uses the (?) formed by electron transport to drive the synthesis of ATP.
Protons flow (?) from the inter membrane space through the ATP synthase protein. which energizes the synthesis of ATP
the proton gradient
The downhill flow of protons (from an area of high
concentration in the intermembrane space to an area of low concentration in the mitochondrial matrix) through the ATP synthase energizes the synthesis of ATP from ADP and inorganic phosphate.
electron transport phase
reduced nucleotides pass their electrons through a series of enzyme bound cofactors. At various
stages of the electron transport system, the downhill transfer of electrons is coupled to the uphill transport of hydrogen ions. The hydrogen ions are pumped from the inner matrix of the mitochondria to the region between the inner and outer
the hydrogen ion gradient, created
by the oxidative proton pumps, is used to drive the synthesis of ATP from ADP and Pi. In this process, the protons flow through an ATPase down their concentration gradient back across the inner
consists of four complexes: Three proton pumps and a physical link to the citric acid cycle.
High potential electrons from NADH enter the system at
Electrons flow from NADH to coenzyme Q through (?).
The flow of electrons through complex I is coupled to the pumping of (?) protons out of the matrix of the mitochondrion into the space between the inner and outer mitochondrial membrane.
Electrons from FADH2 (which have a lower potential than
those from NADH) flow to coenzyme Q through complex (?)
This complex does not pump any protons.
Two electrons are carried through the mitochondrial membrane from complex I or complex II to (?) by reduced coenzyme Q (QH2).
This coenzyme is lipid soluble and always stays in the membrane.
Two electrons flow from (?_ through Q-cytochrome c
oxidoreductase (Complex III) to the water soluble protein (?)
The flow of electrons through complex III is
coupled to the net transport of (?) protons into the space between the inner and outer mitochondrial membrane and the uptake of (?) protons from the mitochondrial matrix.
Each molecule of reduced cytochrome c carries (?) electron(s)
from Q-cytochrome c oxidoreductase to cytochrome c oxidase (complex IIII).
Four electrons from four molecules of cytochrome c flow
through complex IIII to react with (?) and form water as the
final product of the respiratory chain.
There are a number of cofactors that participate in electron
-Non-heme iron sulfur complexes
-Cytochromes b, c1, c, a, a3
There is a significant difference in the absorbance spectrum of NAD+ and NADH. Such alterations in the absorption spectra
occur in various cofactors depending on their oxidation states.
These changes are useful in following the progress of a biochemical reaction.
The first acceptor of electrons from NADH in complex I is
Flavin Mononucleotide (FMN)
The reduction of FMN to FMNH2 occurs on the same (?) ring and has essentially the same chemistry as we have previously
seen with the conversion of FAD to FADH2.
When the FMN cofactor is reduced to FMNH2, it accepts (?) on the isoalloxizine ring
electrons and two protons
The lipid soluble cofactor ubiquinone (aka coenzyme Q) can
The addition of one electron and one proton to coenzyme Q produces a (?) (a free radical with an unpaired electron).
The semiquinone is a very reactive and unstable intermediate that has to be closely sequestered within the active sites of enzymes.
The addition of a second electron and proton to coenzyme Q produces
reduced intermediate ubiquinol.
The coenzyme Q molecule carries electrons within the inner mitochondrial membrane between (?)
It also functions to carry electrons between (?) and also within (?) complex.
The soluble protein cytochrome c shuttles electrons between
The cytochrome proteins all contain (?) groups with a tetrapyrrole organic structure and a central (?)
Similar to many of the molecules in the electron transport chain, cytochrome c has an absorption spectrum. It absorbs light in:
the visible wavelength, giving it a color that is visible to the human eye
Remember that when NADH is the donor, the electrons flow from (?) to (?) and then to complex (?)
complex I (NADH coenzyme Q reductase) to
complex III (coenzyme Q cytochrome c reductase) then to
complex IIII (cytochrome c oxidase)
Complex I (NADH Coenzyme Q Reductase)
Complex III is called
Complex III (Cytochrome c Reductase).
QH2 feeds two electrons into the complex, but cytochrome c only accepts one electron. As a
result, it takes (?) cycles of reduction involving two cytochrome c molecules to effectively convert coenzyme Q from the reduced to oxidized form.
two molecules of reduced coenzyme Q donate (?) electrons.
Two of those
electrons produce two molecules of reduced cytochrome c, and the
other two electrons end up regenerating a molecule of QH2.
What is the best current estimate of the ATP yield in oxidativephosphorylation when FADH2 is the electron donor?
During the process of converting molecular oxygen to water, (?) electrons from reduced cytochrome c and (?) protons from the matrix are used to reduce the two oxygen atoms to water.
In addition to the four “chemical protons” absorbed from the matrix and incorporated into water, four additional protons are pumped from the matrix to the intermembrane space.
Remember that the electron transport process starts with
NADH donating electrons to the system, and finishes with
oxygen receiving electrons to form water.
The Nernst Equation tells us that the reduction potential for any reaction is equal to
the standard state reduction potential plus RT/nFln (electron
The standard state voltage change (ΔE0’) for the
combined reaction equals the standard reduction potential for the electron acceptor (the substance being reduced) minus the
standard reduction potential for the electron donor (the substance being oxidized).
Formula for determining the standard state
free energy change for a reaction if you know the value for the voltage change. That formula is:
Complex IV, which accepts electrons from cytochrome c
and donates them to (?) , has a drop of about (?)
Complex I, which accepts electrons from NADH, passes them through FMN, and donates them to (?) has a
voltage drop of about (?) volts.
Complex III, which starts with
coenzyme Q and ends with(?), has a drop of about (?) volts.
Notice that the role of the electron transport complexes is
to pump protons across the membrane
The connection between electron transport and oxidative phosphorylation is through
synthase complex is made up of an F0 component that is embedded in (?) and the F1 component that is a peripheral protein assembly
The F0 component consists of (?)
different protein subunits, and the F1 component contains (?)
The g subunit passes through the middle of the α 3 β 3
hexamer, which consists of
At any given time, each of the three β subunits exists in a different nucleotide binding form designated (?) These three
forms are interconvertible. The
The α subunits bind ATP but do not
Proton driven ATP synthesis involves a binding change mechanism, in which three sequential 120 degree rotations of the γ subunit drive
the β subunits through three different forms, T (tight),
O (open) and L (loose).
The subunit in the T form converts (?), but does not allow the ATP product to be released.
When the γ subunit is rotated by 120 degrees in a counter
clockwise direction, the T form is converted into
the O form,
allowing ATP release.
Then ADP and Pi can bind to the O form & An additional 120 degree rotation
The membrane spanning F0 component consists of
The c subunit consists of
two α-helix structures with a negatively
charged aspartate in the center.
The c subunit consists of two α-helix structures with a negatively
charged (?) in the center.
The a subunit contains a
Subunit Structure of the F0 Component. Each of the c subunits consists of
Subunit Structure of the F0 Component. Between (?) of the c subunits form a membrane spanning ring.
In summary, each proton enters the cytoplasmic half-channel,
follows a complete rotation of the c ring, and exits through
The flux of protons through the F0
component drives (?) which in turn drives the rotation of the γ subunit of the F1 component.
The rotation of
the γ subunit in turn powers the synthesis of
NADH produced in the glycolysis pathway is located in (?).
However, the NADH is used by the electron transport system in (?)
called the glycerol 3-phosphate shuttle that accomplishes the
translocation of NADH from the cytoplasm to the mitochondria.
The reducing equivalents from cytoplasmic NADH are carried into
the matrix by the
The reducing equivalents from cytoplasmic NADH are carried into the matrix by the glycerol 3-phosphate shuttle.
The end product of this process is (?)
The net cost of this transport is (?)
because FADH2 only yields 1.5 ATP’s in oxidative
In the glycerol 3-phosphate shuttle, electrons from NADH are used to reduce dihydroxyacetone phosphate to (?) which is reoxidized by electron transfer to an (?) of a dehydrogenase that is located in the inner mitochondrial membrane.
***Subsequently, the electrons are
transferred to coenzyme Q, forming QH2
This mechanism is predominate in muscle cells.
Energy Yields in Oxidative Phosphorylation
-Electrons that enter the electron transport system from NADH
yield 2.5 ATP
-Electrons that that enter the electron transport system from FADH2 yield 1.5 ATP
Electrons from NADH:
-Electrons from FADH2:
pass through complex II, which does not
pumps protons, and then go on through complexes III and IV, which do pump protons
An uncoupling protein (UCP-1) acts as a (?). That allows protons to enter the matrix of the mitochondria without passing through (?) This mechanism dissipates the proton gradient and
generates (?) but eliminates (?)
uncouples oxidative phosphorylation.
act like the protein UCP-1 in that they allow
electron transport to proceed in a normal manner, but they dissipate the proton gradient by allowing protons to leak back into the matrix.
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