25 - Oxidative Phosphorylation Flashcards
Mitochondria are a two-membrane system. The (INNER/OUTER) membrane is permeable due to the presence of porin aka VDAC (voltage-dependent anion channels).
Outer
Mitochondria are a two-membrane system. The (INNER/OUTER) membrane is impermeable, has metabolite transporters, and is folded into series of cristae.
Inner
Mitochondria have two compartments, which are…
Intermembrane space
Matrix
This is the site of the TCA cycle and fatty acid oxidation.
Matrix of mitochondria
This occurs in the inner membrane (along membrane) of the mitochondria.
Oxidative phosphorylation
Mitochondria share an __________ relationship with host cell. They have their own DNA, make proteins and RNAs.
Endosymbiotic
Human mitochondrial DNA is (MATERNALLY/PATERNALLY) inherited.
Maternally
The TCA cycle generates ______ and ______. In OxPhos these high energy electrons flow through 4 protein complexes called the electron transfer chain (ETC).
NADH
FADH2
Electrons reduce molecule O2 to _______.
Water
In OxPhos, three of the complexes pump _______ from the matrix to intermembrane space.
Protons
Protons return to the matrix by flowing through another complex called…
ATP synthase
What is the primary function of OxPhos?
ATP synthesis
Which complex in OxPhos does NOT pump protons?
Complex II
A successful OxPhos must accomplish the following key goals:
1) To transfer electrons from _______ and _______ to O2.
2) To establish a _______ gradient across the inner mitochondrial membrane.
3) To synthesize _______.
NADH
FADH2
Proton
ATP
Electrons transferred from NADH to O2 via three large protein complexes, which are…
NADH Q oxidoreductase (Complex I)
Q cytochrome c oxidoreductase (Complex III)
Cytochrome c oxidase (Complex IV)
Electron flow is (EXERGONIC/ENDERGONIC) and powers the flow of protons across the inner membrane.
Exergonic
What is the other complex of the ETC that does not pump protons?
Succinate Q reductase (Complex II)
Succinate Q reductase (Complex II) has ________ ________ which generates FADH2 in the TCA cycle.
Succinate dehydrogenase
Electrons from FADH2 enter through which complex?
Q cytochrome c oxidoreductase (Complex III)
Complex I, III, and IV are called…
Respirasome
This is what transfers electrons from NADH Q oxidoreductase (Complex I) and succinate Q reductase (Complex II) to Q cytochrome c oxidoreductase (Complex III).
Coenzyme Q (Ubiquinone or Q pool)
Coenzyme Q has a long tail made of 5 - C ________ units which makes it hydrophobic.
Isoprene
What is the most common coenzyme Q?
CoQ 10
This is what shuttles electrons from Q cytochrome c oxidoreductase (Complex III) to cytochrome c oxidase (Complex IV). It is the final component of the ETC and catalyzes the reduction of O2 (to water).
Cytochrome c
Complex I, aka NADH Q oxidoreductase (NADH dehydrogenase), is a large protein (>900 kDa, with 46 polypeptide chains) and is encoded by both ________ and _______ genes.
Nuclear
Mitochondrial
This is the first point of entry of electrons from NADH.
NADH Q oxidoreductase (Complex I)
What is the reaction catalyzed by Complex I?
NADH + Q + 5H+ (matrix) —– NAD+ + QH2 + 4H+ (cytoplasm)
These are present in non-heme iron proteins and play a role in reduction reactions. They exist in various configurations.
Iron Sulfur clusters
Iron sulfur clusters undergo oxidation-reduction reactions but the ________ never leave the protein.
Protons
For example, NADH Q oxidoreductase contains _______ and ______ iron sulfur clusters.
2Fe-2S
4Fe-4S
FADH2 enters the ETC through this complex, and it is what connects TCA to OxPhos (succinate dehydrogenase).
Succinate Q reductase (Complex II)
T/F. FADH2 does not leave the complex.
True
FADH2 does not leave the complex. Its electrons are transferred to FeS and then to Q to form QH2. It does not pump protons. Consequently less _______ is synthesized from the oxidation of FADH2.
ATP
Electrons from QH2 are passed on to cytochrome c by what?
Cytochrome c oxidoreductase (Complex III)
The flow of electrons from QH2 to complex III then cytochrome c leads to the transport of _____ protons to the cytoplasmic side.
2
What is the total reaction in complex III?
QH2 + 2 Cyt c(ox) + 2H+(matrix) – Q + 2 Cyt c(red) + 4H+ (cytoplasm)
Cytochrome c oxidase (Complex IV) catalyzes the transfer of electrons from reduced Cyt c to molecular ________, the final acceptor. This is what makes these reactions aerobic and makes humans “breathe”.
Oxygen
_______ electrons are funneled to oxygen to reduce it to water. At the same time, protons are being pumped from matrix to cytoplasmic side of inner membrane.
Four
What is the total reaction of complex IV?
4 Cyt c(red) + 8H+ (matrix) + O2 — 4 Cyt c(ox) + 2 H2O + 4H+ (cytoplasm)
Why does cytochrome c oxidase (Complex IV) have 2 heme and 3 Cu groups?
Because these groups are electron acceptors and donors
The partial reduction of O2 generates highly reactive oxygen derivatives, called…
Reactive oxygen species (ROS)
ROS (reactive oxygen species) are implicated in many pathological conditions. ROS include what?
Superoxide ion (O2-) Peroxide ion (O2(2-)) Hydroxyl radical
T/F. Free radicals are harmful even at low levels.
False. They are not harmful at low levels.
This antioxidant is responsible for reducing superoxide ions into molecular oxygen and oxidizing superoxide ions into hydrogen peroxide.
Superoxide dismutase (SOD)
Hydrogen peroxide is not harmful itself, but it causes problems in DNA by producing what?
Hydroxyl radical
This antioxidant can break down the hydrogen peroxide into molecular oxygen and water.
Catalase
This antioxidant is already present in the body and can also break down hydrogen peroxide.
Glutathione peroxidase
What are 2 other essential antioxidants that people have to consume on their own?
Vitamin E
Vitamin C
Name two types of superoxide dismutase (SOD).
1) Cu/Zn SOD (SOD1) cytosolic
2) Mn/Zn SOD (SOD2) mitochondrial
How do antioxidants work?
They donate an electron to a free radical, keeping the free radical from stealing one from another molecule creating a free radical cascade. Antioxidants stay stable when they donate electrons, preventing them from becoming free radicals.
