Chapter 20: ETC and Chapter 21: Proton-Motive Force Flashcards
Oxidative phosphorylation takes place in _______ and is the major source of _______.
Mitochondria
Energy for aerobic organisms
How much ATP is generated from oxidative phosphorylation?
26 ATP
Electrons flow from NADH and FADH2 to O2 in the ________.
Electron-transport chain or respiratory chain
The electron flow generates a…
Proton gradient that powers ATP synthesis
Collectively, the citric acid cycle and oxidative phosphorylation are called…
Cellular respiration
Outer mitochondrial membrane is ______ while inner mitochondrial membrane is ______.
Outer - permeable
Inner - impermeable
A negative redox potential means that a molecule has…
Lower affinity for electrons compared to H2
A positive redox potential means, the molecule has…
A higher affinity for electrons
A measure of a molecule’s tendency to donate or accept electrons
Redox potential
Only 3 of the 4 protein complexes pump protons. They are…
- NADH-Q oxidoreductase (Complex I)
- Q-cytochrome c oxidoreductase (Complex III)
- Cytochrome c oxidase (Complex IV)
The complex that is not a proton pump is called:
Succinate Q-reductase (Complex II)
These complexes appear to be associated with one another in what is called the _______.
Respirasome
What are the 2 mobile electron carriers?
- Ubiquinone (coenzyme Q or Q)
- Cytocrome C
How many protons are simultaneously pumped out of the mitochondria by Complex I?
Four
Complex III electron transfer is coupled to the pumping of ______.
Two protons from the matrix
Cytochrome c oxidase pumps _______ from matrix to cytoplasmic side
Four protons
(This reaction requires oxygen)
The cytochrome c oxidase complex catalyzes the reduction of molecular oxygen. During this catalysis small amounts of superoxide anions and hydrogen peroxide are released. These are called…
- Reactive oxygen species or ROS.
- ROS are harmful for cells.
- The cells developed mechanisms to deal with ROS .
What % of oxygen molecules consumed by mitochondria are converted into superoxide ions?
2-4%
What two enzymes protect against ROS damage?
Superoxide dismutase and catalase
_________ converts superoxide radicals to hydrogen peroxide and water.
Superoxide dismutase
______ converts hydrogen peroxide into water and oxygen
Catalase
What is the chemiosmotic theory?
Electron transport and ATP synthesis are coupled by a proton gradient across the inner mitochondrial membrane
*ATP synthesis is powered by the proton-motive force
Proton-motive force consists of what two gradients?
- Chemical gradient
- Charge gradient
The chemical gradient of the proton-motive force…
is generated by the difference in pH inside and outside the matrix (outside has more protons and is more acidic than matrix)
The charge gradient of the proton-motive force
is generated by the charge difference inside and outside the matrix (outside has more protons, which is more positive and matrix has less protons and is more negative).
The structure of ATP synthase.
It consists of 2 units
- Fo= proton-conducting unit –contains the proton channel.
- F1= ATP-synthesizing unit, contains the catalytic activity (beta-subunit).
How many protons must flow into the matrix for each ATP formed and released by the b subunit?
Three protons
The __________ accounts for the synthesis of ATP by the b subunit in response to proton flow.
Binding change mechanism
T or F: Cytoplasmic NADH cannot enter the mitochondria.
True
Electrons from cytoplasmic NADH are carried across the mitochondrial membrane by two major mitochondrial shuttles:
- Glycerol 3-phosphate shuttle (muscle)
- Malate-aspartate shuttle (heart and liver)
In muscle, electrons from cytoplasmic NADH enter the electron-transport chain via the ________.
Glycerol 3-phosphate shuttle
Yields 1.5 ATP
In heart and liver, electrons from cytoplasmic NADH are used to generate mitochondrial NADH in ________.
Malate-aspartate shuttle
Yield 2.5 ATP
*No energy loss
The synthesis of 1 ATP requires ______ (____ in ATP synthesis and ____ for ATP transport)
**4 H+ **
3 in synthesis
1 in transport
____ protons are translocated per NADH and ____ protons per FADH2.
10 protons per NADH
6 protons per FADH2
P/O for NADH
P/O = (10 H+/ 4 H+) = 2.5 ATP/O
P/O for FADH2
P/O = (6 H+/ 4 H+) = 1.5 ATP/O
(FADH2 does not pass through complex I)
The________ is the most important factor in determining the rate of oxidative phosphorylation. This regulation is called __________.
- Levels of ADP
- Respiratory control or acceptor control
_______ carry protons across the inner mitochondrial membrane. The electron-transport chain functions, but ATP synthesis does not because the proton gradient can never form.
Uncouplers
Rotenone (fish/insect poison) and amytal (barbiturate sedative)…
Block the electron transfer in NADH-Q oxidoreductase
Antimycin A…
Blocks the electron flow in Q-cytochrome c oxidoreductase
CN-, N3 and CO…
block the electron transfer in cytochrome c oxidase
Oligomycin and dicyclohexylcarbodiimide (DCCD, antifungal agent) inhibits the ATP synthase by…
Preventing the influx of protons.
_________ uncouples electron transport from phosphorylation in mitochondria by carrying the protons across the inner mitochondrial membrane. It stops ATP synthesis without affecting electron transport from NADH to O2
2,4-Dinitrophenol (DNP)
NADH is a strong ________ agent and has a ________ redox potential (E0).
Reducing agent
Negative redox potential
In an experiment, oxidative phosphorylation is inhibited by Antimycin A. Which one of the following molecules will be in the reduced state (received electrons)?
Ubiquinone Q
Cyctochrome c, a small soluble protein, shuttles electrons from Q-cytochrome c oxidoreductase to:
Cytochrome C oxidase
In oxidative phosphorylation, the transfer of electrons from NADH to O2 leads to pumping of _________ protons (H+) from the mitochondrial matrix to the intermembrane space.
10
T or F: The electron transport chain generates a proton gradient that is required for NADH production.
False
The F1 subunit of the ATP synthase is also known as…
ATP synthesizing unit
