Oxidative Phosphorylation part 1: Electron Transport Chain

ATP

after two turns of the TCA cycle, six carbons are gone (6 CO2), and all we have left are
electrons carried by NADH and FADH2 and what

Oxidative phosphorylation

captures the energy in high-energy electrons from the oxidation of glucose and uses it to synthesize ATP

The flow of electrons from NADH and FADH2 to O2 occurs in the what

The flow of electrons from NADH and FADH2 to O2 occurs in the what

respiration

Collectively, the citric acid cycle and oxidative phosphorylation are called cellular what, or simply what

Respiration is an ATP-generating process in which an inorganic compound (such as molecular oxygen) serves as the ultimate electron what

acceptor

The use of oxygen as the final electron acceptor to accept the high energy electrons from the citric acid cycle is what makes some organisms what

aerobes

Other organisms (mostly bacteria) do anaerobic respiration with final electron acceptors that are not oxygen to produce ATP, which it is much more or less effective/efficient

less

The inner mitochondrial membrane, which is folded into ridges called cristae, is what to most molecules

impermeable

matrix

The inside of the mitochondrion is called the what

matrix

The citric acid cycle and fatty acid oxidation occur where

Which membrane is the site of electron transport and ATP synthesis

inner

What is pumped into the space between the inner and outer membranes

Protons

Glycolysis

cytoplasm

TCA cycle

mitochondrial matrix

Electron transport chain (ETC)

mitochondrial inner membrane

electron

The what transport chain involves the flow of electrons from molecule to molecule in a series of linked redox reactions, ultimately ending with O2

Redox

The electron-transfer potential of a molecule is referred
to as Reduction or what Potential

reduction potential E0′

a measure of a molecule’s tendency to donate or accept electrons

the acceptor of electrons in an oxidation–reduction reaction

oxidant (oxidizing agent)

the donor of electrons in an oxidation–reduction reaction

reductant (reducing agent)

Oxidants have a what E0′.

positive

Reductants have a what E0′.

negative

water

electrons from NADH from the TCA cycle reduce oxygen to what

gradient

DG°’ = -220 kJ/mol from one NADH!
This energy is used by the complexes of the ETC to pump protons across the mitochondrial membrane to create what

The Electron-Transport Chain is how Large Complexes in the Inner Mitochondrial Membrane

4

Complex ? accepts electrons from NADH

I

Complex ? accepts electrons from FADH2

II

Which complex does not pump protons

II

intermembrane

Complexes (I, III, IV) pump protons out of the mitochondrial matrix, across the inner mitochondrial membrane, into the what space, generating a proton gradient

Electrons are accepted at the end of the ETC by what

O2

ubiquinone

In addition, there are two mobile components that carry
electrons between complexes
- coenzyme Q/what and cytochrome c

chemical

The complexes have more what names too. The name tells you where the electrons come from and where they end up, for each complex

NADH-Q oxidoreductase

Complex I

Cytochrome c oxidase

Complex IV

Q-cytochrome c oxidoreductase

Complex III

succinate Q-reductase

Complex II

In Complex I NADH donates electrons to where

Coenzyme Q/Ubiquinone

In Complex II succinate/FADH₂ donates electrons to where

Coenzyme Q/Ubiquinone

In Complex III Coenzyme Q/Ubiquinone donates electrons to where

Cytochrome C

In Complex IV Cytochrome C donates electrons to where

Oxygen

NADH and FADH2 donate electrons, which travel through the ETC to the final electron what O2

acceptor

affinity

Inside each complex there is a series of electron carrying compounds with increasing what for electrons

NADH and FADH2 will donate electrons to the first compound, and then the electrons will flow down to the what affinity acceptor at the bottom of each complex

high

flavin

The intermediate electron carriers in the four ETC complexes:
- what mononucleotide (FMN)

copper

The intermediate electron carriers in the four ETC complexes:
- free what

iron

The intermediate electron carriers in the four ETC complexes:
- what associated with sulfur in proteins (what–sulfur proteins)

cytochromes

The intermediate electron carriers in the four ETC complexes:
- iron in heme embedded in proteins called what

The intermediate electron carriers in the four ETC complexes:
- a mobile electron carrier called coenzyme what (what)

Q

Which Complex Contains Copper Ions

IV

Complex IV Contains Copper Ions
the copper cycles between its oxidized form what and its reduced form what

Cu2+, Cu+

Structure of Iron–Sulfur Clusters
the iron cycles between its oxidized form what and its reduced form what
gained one e

Fe3+, Fe2+

heme

Cytochromes (a, b, c) are proteins in the respiratory chain that contain what

Coenzyme Q has a long hydrophobic side chain made of how many carbon
repeats (10X is common) which make it mobile in the membrane

5

Coenzyme Q can exist in several oxidation states because it accepts
one electron at a time:
fully oxidized

ubiquinone/Q

Coenzyme Q can exist in several oxidation states because it accepts
one electron at a time:
partially oxidized/reduced

QH

Coenzyme Q can exist in several oxidation states because it accepts
one electron at a time:
fully reduced

ubiquinol/QH2

Q pool

Oxidized and reduced Q are present in the inner mitochondrial membrane in what is called the what

matrix

Conformational changes caused by binding and reduction of Q in the matrix
part of the complex are translated to other parts of the complex in the membrane,
which open and close pockets that allow protons to move from the what, through
the membrane into the space between the inner and outer mitochondrial membranes

The electrons from NADH enter Complex I and are passed to FMN then
to iron-sulfur complexes then to Q, which is reduced to what

QH2

QH2 leaves the enzyme for the Q pool in the what interior of the
inner mitochondrial membrane.

hydrophobic

The energy from the movement of these electrons is used to pump how many
protons out of the mitochondrial matrix into the intermembrane space

4

FADH2 has a less negative reduction potential than NADH, so it enters the chain at which step

second

FADH2 has a less negative reduction potential than NADH, so it enters the chain at the second step
therefore, FADH2 pumps how many protons than NADH and creates how many ATP molecules

fewer, fewer

The citric acid cycle enzyme succinate dehydrogenase is actually
part of Complex what in the inner mitochondrial membrane

II

matrix

Electrons from FADH2 Enter at Complex II
This is the only enzymatic reaction of the citric acid cycle that does
not take place in the mitochondrial what

The FADH2 generated by succinate dehydrogenase doesn’t leave or leaves the complex and transfers its electrons directly to iron-sulfur complexes and ultimately to Q, reducing it to QH2, which then enters the Q pool

doesn’t leave

mobile

Reduced Q (QH2) from complexes I and II forms the Q pool which
is what in the mitochondrial inner membrane

Reduced Q enters Complex ?

III

Reduced Q enters Complex III. Electrons from QH2 pass through cytochrome b to iron-sulfur complexes and finally are used to reduce how many molecules of cytochrome c

2

Complex III uses the energy released from electron transfer to pump how many protons into the intermembrane space

4

Electrons Flow from Ubiquinol to Cytochrome ? Through Complex III

C

QH2 carries how many electrons, whereas cytochrome c carries how many electrons

2, 1

Q cycle

The mechanism for coupling electron transfer from QH2 to cytochrome c is
called the what

intermembrane

cytochrome c:
– mobile - moves through the what space

cytochrome c:
– carries a single electron from Complex what to Complex what using iron in a heme group

III to IV

Complex IV accepts four electrons from four molecules of cytochrome c, passes them through heme and Cu+ and finally uses them to what O2 to two molecules of H2O

reduce

In the cytochrome c oxidase reaction, how many protons are removed
from the matrix

8

chemical protons

In the cytochrome c oxidase reaction, eight protons are removed
from the matrix. Four protons, called what, are used to reduce oxygen.

intermembrane

In the cytochrome c oxidase reaction, eight protons are removed from the matrix. Four protons, called chemical protons, are used to reduce oxygen. In addition, four protons are pumped into the what space

respirasome

We currently believe the 4 large complexes are associated together in a supramolecular complex that has been called the what

Flow of Electrons and Protons through the
Electron Transport Chain
2NADH + 22H+matrix + O2 → 2NAD+ + 20H+pumped + 2H2O
how many protons are pumped into the intermembrane space per NADH

10

The transfer of one electron generates ’what’ (O2-)

superoxide

The transfer of two electrons generates what (O2^2-)

superoxide

reactive oxygen species (ROS)

superoxide (O2-), peroxide (O22-), along with hydroxyl radical (OH°) these are
called what

ROS react with all cellular biomolecules (proteins, nucleotides,
membranes) and does what to them. This is implicated in many pathological conditions and may be one basis of cellular aging

damage

what Radicals are Scavenged by Protective Enzymes to Protect Cells

Superoxide

dismutase

Superoxide what converts superoxide into hydrogen peroxide

catalase

What cleaves hydrogen peroxide into oxygen and water

mitochondria

In mammals, the mutation rate for mitochondrial DNA is 10- to 20- fold
higher than for nuclear DNA. This higher rate is believed to be due to
the inevitable generation of reactive oxygen species by oxidative
phosphorylation in what