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94 Cards in this Set
- Front
- Back
The early Earth was populated by anaerobes. How did they capture and utilize energy?
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by oxygen-independent metabolism
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When did oxygen accumulate in the primitive atmosphere?
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after cyanobacteria appeared
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How have aerobes evolved from anaerobes?
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to use oxygen to extract more energy from organic molecules
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Where does aerobic respiration take place in eukaryotes?
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in the mitochondrion
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How are mitochondria shaped?
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typical mitochondria are bean-shaped organelles but they can also be round or threadlike
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Which characteristics of mitochondria reflect the energy requirements of the cell?
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size and number of mitochondria
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The balance between fusion and fission is likely a major determinant of which three characteristics?
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mitochondrial number, length, and degree of interconnection
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Describe mitochondria when fusion becomes more frequent than fission.
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mitochondria tend to become more elongated and interconnected
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Describe mitochondria when fission becomes more frequent than fusion.
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there are more numerous and distinct mitochondria
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What does the number and size of mitochondria in a cell depend upon?
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the role of the cell
the body's condition(s) |
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It has been known for many years that mitochondria and endoplasmic reticulum (ER) engage in extensive interactions. What was discovered to be induced via this contact?
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mitochondrial fission--> induced by contact with thin tubules from the ER
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Mitochondria can be split or joined, but they can also...
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replicate independently of the host cell. This is important for muscle development.
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How many membranes does the outer boundary of a mitochondrion contain?
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two - outer and inner
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Describe the outer membrane of mitochondria.
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serves as the mitochondrion's outer boundary
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Describe the inner membrane of mitochondria.
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subdivided into two interconnected domains:
inner boundary membrane - forms a double membrane outer envelope cristae - where the machinery for ATP is located |
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Mitochondria have an inner membrane that is folded. What is the significance of this?
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This increases membrane surface area and allows many reactions that generate ATP to take place on the cristae.
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The membranes of the mitochondrion divide the organelle into two aqueous compartments. Describe them.
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matrix - (within the interior of the mitochondrion) has a gel-like consistency due to the high concentration of water-soluble proteins
intermembrane space - proteins located in this space are known for their role in initiating cell suicide |
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What does the mitochondrial matrix consist of and what can be synthesized in it?
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contains a circular DNA molecule, ribosomes, and enzymes
RNA and proteins can be synthesized in the matrix. |
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The outer and inner membranes of mitochondria have very different properties. What is the outer membrane composed of?
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~50% lipid by weight and contains a mixture of enzymes involved in diverse activities
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The outer and inner membranes of mitochondria have very different properties. What is the inner membrane composed of?
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contains more than 100 different polypeptides and has a very high (3:1) protein/lipid ratio; made of more than 75% protein
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The inner membrane of mitochondria contains no _______________, but is rich in an unusual phospholipid, _________________. What is the significance of this?
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no cholesterol
rich in cardiolipin These are characteristics of bacterial plasma membranes, from which the inner mitochondrial membrane has presumably evolved. |
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The outer membrane of mitochondria contains ________________.
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a large pore-forming protein called porin
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Is the inner membrane permeable or impermeable? Outer membrane?
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inner membrane - impermeable, even to small molecules
outer membrane - permeable to even some proteins |
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The reactions of glycolysis generate ___________ and ____________ in the cytosol.
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pyruvate and NADH
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List the steps of glycolysis.
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1) Glucose is phosphorylated. Lose 1 ATP. Enzyme: hexokinase.
2) Rearrange Glucose 6-phosphate --> Fructose 6-phosphate 3) Fructose 6-phosphate is phosphorylated. Lose 1 ATP. Enzyme: phosphofructokinase. RATE LIMITING STEP 4) Cleave into two isomers. 5) Rearrange dihydroxyacetone phosphate to glyceraldehyde-3 phosphate (isomerization step). 6) Dump a hydrogen, gain a low-energy phosphate. 7) Remove the phosphate on carbon 1. Gain 1 ATP per substrate. Enzyme: phosphoglycerate kinase. 8) Rearrange: move the phosphate from carbon 3 to carbon 2. 9) Dehydrate: lose water. 10) Remove the final phosphate from carbon 2. Gain 1 ATP per substrate. Enzyme: pyruvate kinase. |
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What is the significance of steps 1 and 3 of glycolysis?
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phosphate groups are transferred from ATP to the six-carbon sugar to produce fructose 1,6-bisphosphate
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What is the significance of step 6 of glycolysis?
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oxidation and phosphorylation of glyceraldehyde 3-phosphate to produce 1,3-bisphosphoglycerate and NADH
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What is the significance of steps 7 and 10 of glycolysis?
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transfer of phosphate groups from three-carbon phosphorylated substrates to ADP to produce ATP by substrate phosphorylation
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What is the cyclic pathway that acetyl CoA takes where the substrate is oxidized and its energy is conserved?
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tricarboxylic acid cycle (TCA cycle) also known as the Kreb's Cycle
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What is generated from the first step of the Kreb's cycle?
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1 NADH and 1 CO2
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What is generated from the second step of the Kreb's cycle?
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citrate
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What is the rate limiting step of the Kreb's cycle?
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step 4
1 NADH and 1 CO2 per glucose. This forms alpha-ketoglutarate. |
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What is generated in step 5 of the Kreb's cycle?
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1 NADH and 1 CO2
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What is generated in step 9 of the Kreb's cycle?
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1 NADH
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Summarize the Kreb's cycle.
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4 reactions in the cycle transfer a pair of electrons to NAD+ to form NADH, or to FAD+ to form FADH2.
form 1 GTP by substrate-level phosphorylation release 3 CO2 |
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Reaction intermediates in the TCA cycle are common compounds generated in other catabolic reactions. What is the significance of this?
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This makes the TCA cycle the central metabolic pathway of the cell.
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Fatty acids and proteins typically form ____________.
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acetyl CoA
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Where does oxaloacetate come from?
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typically comes from carbs, but can also come from Asn, Asp
Carbs are easier--they're just converted to glucose or fructose first and fit into glycolysis. The Kreb's cycle will not run without oxaloacetate, which is why carbs are important. |
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What are the primary products of the TCA cycle?
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the reduced coenzymes FADH2 and NADH
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How does NADH formed from glycolysis enter the mitochondria?
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via malate-aspartate (proteins as energy) --> reduce NADH to NAD+
OR glycerol-phosphate shuttles (fats as energy) --> produces FADH2 |
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What is the role of the glycerol phosphate shuttle?
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electrons are transferred from NADH to DHAP to form glycerol 3-phosphate, then to FAD to form FADH
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What is pumped out of the across the inner membrane as electrons move through the electron-transport chain?
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H+
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Summarize the two step process of oxidative phosphorylation.
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formation and harnessing of the proton gradient
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What is the term that describes the coupling of H+ translocation to ATP synthesis?
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chemiosmosis
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How many molecules of ATP are formed from each pair of electrons donated by NADH?
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three molecules of ATP
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How many molecules of ATP are formed from each pair of electrons donated by FADH2?
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two molecules of ATP
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What provides the energy required to phosphorylate ADP to ATP?
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the controlled movements of protons back across the membrane through the ATP-synthesizing enzyme
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What two ways can ATP be formed in the mitochondria?
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substrate-level phosphorylation
OR oxidative phosphorylation --> accounts for more than 160 kg of ATP in our bodies per day |
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Strong oxidizing agents have a ______________ affinity for electrons, while strong reducing agents have a _____________ affinity for electrons.
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strong oxidizing agents - high affinity
strong reducing agents - weak affinity |
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Redox reactions are accompanied by a _____________ in free energy.
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decrease
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What is the term that describes the measure of charge separation caused by the transfer of electrons?
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redox potential
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If electrons flow from the sample half-cell to the reference half-cell, the standard redox potential of the sample couple is _____________.
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negative (preferential)
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If electrons flow from the reference half-cell to the sample half-cell, the standard redox potential of the sample couple is ______________.
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positive
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How do electrons move through the inner membrane of the mitochondrion?
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via a series of carriers of decreasing redox potential
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Which specific electron carriers transfer electrons associated with either NADH or FADH2?
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carriers that make up the electron transport chain
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Which electron carriers are polypeptides bound to either FAD or FMN?
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flavoproteins
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Which electron carriers contain heme groups bearing Fe or Cu metal ions?
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cytochromes
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Which electron carriers are located within a single protein complex and alternate between Cu2+/Cu3+?
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three copper atoms
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Which electron carriers consist of a lipid-soluble made of five-carbon isoprenoid units?
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ubiquinone
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Which electron carriers contain Fe in association with inorganic sulfur?
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iron-sulfur proteins
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The energy level of the (negatively charged) electrons _______________ with each step of increasingly positive redox potential.
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decreases
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Describe complex I of the electron-transport complexes.
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(NADH dehydrogenase) catalyzes transfer of electrons from NADH to ubiquinone and transports four H+ per pair
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Describe complex III of the electron-transport complexes.
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(cytochrome bc1) catalyzes the transfer of electrons from ubiquinone to cytochrome c and transports four H+ per pair
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Describe complex II of the electron-transport complexes.
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(succinate dehydrogenase) catalyzes transfer of electrons from succinate to FAD to ubiquinone without transport of H+
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Describe complex IV of the electron-transport complexes.
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(cytochrome c oxidase) catalyzes transfer of electrons to O2 and transports H+ across the inner membrane
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What is a large complex that adds four electrons to O2 to form two molecules of H2O?
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cytochrome oxidase
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Which metabolic poisons bind catalytic sites in complex IV?
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CO, N3-, and CN-
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What is the gateway to the electron-transport chain?
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complex I
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Describe what complex I consists of.
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Complex I contains a peripheral hydrophilic domain and a membrane-embedded hydrophobic domain.
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What is electron transfer in the peripheral hydrophilic arm of complex I coupled with?
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conformational changes to proton translocation across the membrane domain
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What promotes proton translocation in complex I?
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unprotonated glutamic acid and protonated lysine residues driven by transmembrane helix conformational changes
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What is the term that describes the proton pump in synthetic liposomes that adds four electrons to O2 to form two molecules of H2O (complex IV)?
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cytochrome oxidase
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What rate are electrons transferred in complex IV?
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one at a time
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What is thought to drive conformational changes in complex IV? What do these changes promote?
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energy released by O2 reduction
These changes promote H+ ions movement through protein |
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What does the tendency for electrons to be transferred from one carrier to the next depend upon?
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the energy potential difference between the two redox centers
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What does the rate of transfer of electrons depend upon?
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the catalytic activities of the proteins involved
Electrons may travel 10-20A (considerable distances) between adjacent redox centers. |
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What is the term that describes the route in which electrons probably flow that consists of a series of covalent and hydrogen bonds that stretch across parts of several amino acid residues?
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tunneling pathways
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Explain the two components of the proton gradient.
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pH gradient (ΔpH) - created by the concentration gradient between matrix and intermembrane space
electric potential (Ψ) - results from the separation of charge across the membrane |
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What is the term that describes energy present in both components of the proton gradient?
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proton-motive force (Δp)
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What uncouples glucose oxidation and ATP formation? How?
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Ditrophenol (DNP) uncouples glucose oxidation and ATP formation by increasing the permeability of the inner membrane to H+, thus eliminating the proton gradient
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What accounts for differences in metabolic rate?
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differences in uncoupling proteins (UCP)
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What did the isolation of coupling factor 1, or F1, show? What is the significance of this?
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it hydrolyzed ATP
Under experimental conditions, it acts as an ATP synthase. This led to the conclusion that an ionic gradient establishes a proton-motive force to phosphorylate ADP. |
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What are the two major portions of ATP synthase? Explain.
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F1 - catalytic subunit, contains 3 catalytic sites for ATP synthesis
F0 - attaches to the F1 and is embedded in the inner membrane; base contains a channel through which protons are conducted from the intermembrane space to the matrix |
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How many structural units are in the c ring of ATP synthase?
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10-14 subunits (varies depending on the source of the enzyme)
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Both the yeast mitochondrial and E. coli ATP synthase have _____ c subunits.
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10
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The chloroplast ATP synthase has _____ c subunits.
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14
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Describe the F0 mechanism.
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The c subunits of the F0 base form a ring.
Protons moving through the membrane rotate the ring. The rotation provides a twisting force that drives ATP synthesis. |
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Binding sites on the catalytic subunit F1 can be _______, ___________, or __________.
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open, loose, or tight
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What is the special peroxisome that plants contain? What does it do?
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glyoxysome - converts fatty acids to glucose by germinating seedlings
(why seeds and nuts are oil-rich) |
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What is the term that describes membrane-bound vesicles that contain oxidative enzymes which carry out the two-step reduction of molecular oxygen to water?
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peroxisomes
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What is the function of peroxisomes?
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oxidize very-long-chain fatty acids and synthesize plasmalogens (a class of phospholipids)
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What drives the transport of ADP into and ATP out of the mitochondrion?
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H+ gradient
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What is the most important factor controlling the respiration rate in a mitochondrion?
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ADP
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What alters the binding affinity of the active site during the ATPase mechanism?
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movement of protons through ATP synthase
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