Chapter 10: Carbohydrate Metabolism II: Aerobic Respiration Flashcards

Question

What are the eight key reactions of the citric acid cycle?

Answer 1

Citrate formation Citrate is isomerized to isocitrate Alpha Ketoglutarate and CO2 formation Succinyl CoA and CO2 formation Succinate formation Fumarate formation Malate formation Oxaloacetate formed anew

Answer 2

Citrate formation. 2C acetyl Coa and 4C oxaloacetate makes 6 carbon citrate and CoA. Condensation reaction, yielding citrate CoA-Sh, catalyzed by citrate synthase. Recall that synthases are enzymes that form new covalent bonds without needing significant energy.

Answer 3

Citrate isomerized to one of four isomers of isocitrate, the goal being d isocitrate.

Answer 4

RATE LIMITING Alpha ketoglutarate and CO2 formation Isocitrate is oxidized to oxalosuccinate, oxalosuccinate decarboxylated to alpha ketoglutarate.

Answer 5

Succinyl CoA and CO2 formation carried out by alpha ketoglutarate dehydrogenase complex (similar in mechanism, cofactors, and coenzymes to the pyruvate dehydrogenase complex). Produces NADH and CO2.

Answer 6

Succinate formation. Hydrolysis of the thioester bond of succinyl CoA yields succinate and GTP CoA-SH. Succinyl CoA synthetase catalyzes this. (Synthetases create new bonds with energy input, unlike synthases). The energy required for the synthetase to work is found in the high energy thioester bond of succinyl CoA. THIS IS THE ONLY TIME IN THE ENTIRE CITRIC ACID CYCLE THAT ATP IS PRODUCED DIRECTLY. The GTP produced in this reaction is transformed into ATP by nucleosidediphosphate kinase.

Answer 7

Fumarate formation. It doesn’t take place in the mitochondrial matrix, occurs on the inner membrane. Succinate oxidation to fumarate by succinate dehydrogenase, an integral protein in the inner mitochondrial membrane. FAD is reduced to FADH2. Each molecule of FADH produces 1.5 ATP (NADH produces 2.5 ATP) FAD is the electronic acceptor in this reaction because the red reducing power of succinate is not great enough to reduce NAD+.

Answer 8

Malate formation. Fumarase catalyzes the hydrolysis of the alkene bond of fumarate to form L malate.

Answer 9

Malate dehydrogenase reduces NAD+ to make NADH by the oxidation of malate to produce oxaloacetate.

Answer 10

Step 3, 4, and 8 produce one NADH. Step 6 produces FADH2. Step 5 produces ATP The fourth NADH comes from the Pyruvate dehydrogenase complex.

Answer 11

High energy molecules (ATP) and energy carriers (NADH and FADH2), which are products of the process. Citrate also inhibits the citric acid cycle (krebs cycle and tricarboxylic acid cycle)

Answer 12

Dehydrogenases are oxidoreductases (they catalyze redox reactions). Dehydrogenases transfer a hydride ion (H-) to an electron acceptor like NAD+ and FAD. Whenever we see a dehydrogenase in aerobic metabolism, look for a high energy electron acceptor being formed.

Answer 13

Complete oxidation of carbons and intermediates to CO2 so that reduction reactions can be coupled with CO2 formation, thus forming energy carrier such as NADH and FADH2 for the electron transport chain.

Answer 14

Isocitrate dehydrogenase, step 3.

Answer 15

The electron transport chain is the final pathway that utilized electrons from our energy source (füd). The flow of electrons happen in a step wise fashion to allow for smaller portions of manageable energy to be exploited rather than one large energy transfer. The ETC occurs in the mitochondrion and involves the intermembrane space, the inner mitochondrial membrane, and the mitochondrial matrix. The complexes, or the energy producing machinery, involved in the ETC are embedded in the inner mitochondrial membrane.

Answer 16

Glycolysis and fermentation occur in the cytosol. The citric acid cycle takes place in the mitochondrial matrix.

Answer 17

Step 6 of the citric acid cycle, the oxidation of succinate to fumarate through succinate dehydrogenase, actually occurs at complex 2 of the electron transport chain. FADH2 is covalently bonded to complex 2, meaning the oxidation of FADH2 for the electron transport chain happens inside of complex 2.

Answer 18

The inner mitochondrial membrane is assembled into folds called cristae (kris-tay), which maximize surface area.

Answer 19

The proton motive force is an electrochemical proton gradient generated by the complexes of the electron transport chain.

Answer 20

The electron transport along the inner mitochondrial membrane and the generation of ATP via ADP phosphorylation. These two processes are separate, but they are coupled so they are often explained together. NADH and FADH2 are form is byproducts at earlier steps and respiration. They transferred their electrons to carry your proteins located along the inner mitochondrial membrane, using oxygen is the final electron acceptor, forming water. Energy released from transporting electrons facilitates, proton transport at three locations in the chain. Protons are moved into the intermembrane space, creating a greater concentration gradient of hydrogen ions that can be used to drive ATP production.

Answer 21

ETC: endergonic ATP synthesis: exergonic They coupling these reactions, the energy yielded by one reaction can fuel the other. The electron transport chain is a series of oxidation and reductions that occur via the same mechanism. NADH and FADH2 are good electron donors (FADH2 being a weaker reducing agent than NADH)

Answer 22

NADH CoQ oxidoreductase. The transfer of electrons from NADH to coenzyme Q is catalyzed in the First complex. Three noteworthy sub units are a flavoprotein that oxidizes NADH, a protein that has an iron-sulfur cluster and coenzyme Q The flavoprotein has a coenzyme called flavin mononucleotide (FMN) covalently bonded to it that is similar to FAD. All three, the FMN (first), the iron-sulfur clusters (second), and CoQ (final), undergo oxidation reduction reactions that ultimately lead to pumping 4 H+ out of the inner mitochondrial matrix.

Answer 23

The effect is 4 H+ ions pumped out of the mitochondrial matrix.

Answer 24

Succinate CoQ oxidoreductase Linked to the step 6 of citric acid cycle. Succinate oxidizes to fumarate via succinate dehydrogenase, reducing FAD to FADH2. This is super interesting. It uses covalently bonded FAD as an electron acceptor because the oxidizing strength of succinate is insufficient to reduce NAD+. FADH2 then gets oxidized to FAD as it reduces another iron-sulphur protein. The final step is oxidation of the Fe-S complex to reduce CoQ. NO H+ PUMPING IN COMPLEX 2.

Answer 25

No H+ are transferred out of the mitochondrial matrix from the redox reactions in complex 2.

Answer 26

CoQH2 cytochrome c oxidoreductase (aka cytochrome reductase) Transfers electrons from CoQ to cytochrome c in a few steps. Redox of CYTOCHROMES: proteins with heme groups in which iron is reduced to Fe2+ and oxidized to Fe3+. The electron transfers from iron only involves one electron per reaction, but because coenzyme Q has two electrons to transfer, two cytochrome C molecules are needed. Transfers four H+ out of the mitochondrial matrix.

Answer 27

Complex 3 main contribution to the proton motive force is via the Q cycle. Two electrons are shuttled from a molecule of ubiquinol (CoQH2) near the enter membrane space to a molecule of ubiquinone (CoQ) near the mitochondrial matrix. Another two electrons are attached to heme moieties, reducing two molecules of cytochrome c. A carrier containing iron and sulfur assists this process. Four protons are displaced to the inter membrane space during the redox reactions of complex three.

Answer 28

Both CoQ and cyt c are not technically part of the complexes. However, because both are able to move freely in the mitochondrial membrane, this degree of mobility allows these carriers to transfer electrons by physically interacting with the next component of the transport chain.

Answer 29

Cytochrome c oxidase Facilitates the culminating step of the electron transport chain: transfer of electrons from cytochrome C to oxygen. Include subunits of cytochrome a, cytochrome a3, and copper ions (Cu2+). Cyt a and a3 make up cytochrome oxidase. Cytochrome oxidase gets oxidized as oxygen is reduced to water. Two H+ are moved across the membrane.

Answer 30

Cyanide is an inhibitor of cytochrome subunits a and a3. The cyanide and ion is able to attach to the iron group and prevent the transfer of electrons. Tissues that rely heavily on aerobic respiration such as the heart in the central nervous system can be greatly impacted.

Answer 31

A proton gradient is formed as electrons were passed along the electron transport chain. This causes two things: PH drops in the intermembrane space. The voltage difference between the membrane space and matrix increases due to proton pumping. These two changes contribute to what is referred as an electrochemical gradient. Electrochemical gradients store energy. Because it is based on protons, we often refer to the electrochemical gradient across the inner mitochondria membrane has the proton motor force. This particular electrochemical gradient will be responsible for providing the energy to ATP synthase to form ATP from ADP and an inorganic phosphate.

Answer 32

Efficiency of aerobic respiration varies between cells. This variable efficiency is caused by the fact that cytosolic NADH formed through glycolysis cannot directly cross into the mitochondrial matrix, meaning it cannot contribute its electrons to the transport chain directly. The alternative means of transportation of these electrons is referred to as shuttle mechanisms. The two shuttle mechanisms that transfer the high energy electrons of NADH to a carrier that can cross the inner mitochondrial membrane are: Glycerol 3 phosphate shuffle Malate-aspartate shuffle

Answer 33

Because NADH formed through glycolysis cannot directly cross into the mitochondrial matrix, it must find alternate means of transportation called shuttle mechanisms. Glycerol 3 phosphate is one of those shuttle mechanisms.

Answer 34

Because NADH formed through glycolysis cannot directly cross into the mitochondrial matrix, it must find alternate means of transportation called shuttle mechanisms. Malate-aspartate shuttle is one of those shuttle mechanisms.

Answer 35

The electron transport chain generates the proton motive force, an electrochemical gradient across the inner mitochondrial membrane which provides the energy for ATP synthase to function.

Answer 36

The malate-aspartate shuttle. Because this mechanism is the more efficient one, it makes sense for a highly aerobic organ, such as the heart to utilize it in order to maximize its ATP yield.

Answer 37

A small fraction, 13/100 polypeptides necessary for oxidative phosphorylation, are encoded by mitochondrial DNA. The significance of this fact is that mitochondrial DNA has a mutation rate nearly 10 times higher than that of nuclear DNA

Answer 38

ATP synthase, which spans the entire inner mitochondrial membrane and protrudes into the matrix.

Answer 39

The F0 portion functions as an ion channel and spans the entire inner mitochondrial membrane. Protons travel through F0 along their gradient back into the matrix.

Answer 40

Chemiosmotic coupling describes the direct relationship between the proton gradient and ATP synthesis. Chemiosmotic coupling allows the chemical energy of the proton gradient to be harnessed as a means of phosphorylating ADP, forming ATP. The ETC generates a high concentration of protons in the inter membrane space; the protons then flow through the F0 ion channel of ATP synthase back into the matrix, where F1 phosphorylates ATP.

Answer 41

The F1 portion of ATP synthase utilizes the energy released from the electrochemical gradient to phosphorylate ADP to ATP.

Answer 42

Conformational coupling suggests that ATP is released by the synthesis as a result of confirmational changed caused by the gradient. This proposed mechanism suggests the F1 portion of ATP synthase is reminiscent of a turbine, spinning with a stationary compartment to facilitate the harnessing of gradient energy for chemical bonding.

Answer 43

Uncouplers are compounds that prevent ATP synthesis without affecting the electron transport chain, decreasing the efficiency of the ETC/oxidative phosphorylation pathway. ADP builds up and ATP synthesis decreases, the body responds to this perceived lack of energy by increasing O2 consumption and NADH oxidation. The energy produced from the transport of electrons is released as heat. An example would be the fever experienced with toxic levels of salicylates, or aspirin.

Answer 44

Always think of O2 and ADP as the key regulators of oxidative phosphorylation. If O2 is limited, the rate of oxidative phosphorylation decreases, and the concentrations of NADH and FADH2 increase. The accumulation of NADH inhibits the citric acid cycle. The coordinated regulation of these pathways is known as respiratory control. In the presence of adequate O2, the rate of oxidative phosphorylation is depending on the availability of ADP as the concentration of ADP and ATP our reciprocally related. Thus, ADP accumulation signals the need for ATP synthesis. ADP allosterically activates isocitrate dehydrogenase (step three of the citric acid cycle) increasing the rate of the citric acid cycle and production of NADH and FADH2. The elevated levels of NADH and FADH2 (reduced coenzymes) increase the rate of electron transport and ATP synthesis.

Answer 45

Isocitrate dehydrogenase is step three of the citric acid cycle and is the rate limiting step of the citric acid cycle (alpha ketoglutarate and CO2 formation and reduction of NAD+ to form NADH). This step, catalyzed by isocitrate dehydrogenase, is regulated by ADP and ATP, with ADP stimulating and ATP inhibiting the enzyme.