Term
True/False Energy is stored in speacial high-energy bonds in molecules such as ATP and is released when these bonds are broken |
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Definition
False; energy is always required to break a covalent bond, including the phosphanhydride bond that links the terminal phosphate group to the rest of the ATP molecule. ATP is a "high-energy" compound because its hydrolysis is exergonic, which means thatmore energy is releae as the bonds between the -H and -OH groups of water are formed than is required to break the phosphoanhydride bond of ATP |
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Term
True/False Energy is always released whenever a covalent bond is formed and is always required to break a covalent bond. |
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Definition
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Term
True/False To a physical chemist, high-enregy bond means a vary stable bond that requires a lot of energy to break, wherease to a biochemist, the term is likely to mean that a release of a lot of energy upon hydrolysis |
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Definition
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Term
True/ False The terminal phosphate of ATP is a high-energy phosphate that takes its high energy with it when it is hydrolyzed. |
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Definition
False; The phosphate group doesn't posses any intrinsic energy of its own. The term high-energy applies only to the phosphoanhydride bond that links the phoshphate group to the rest of the ATP molecule. |
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Term
True/ False Phosphoester bonds are low-energy bonds beacuase they require less energy to break than the high-energy bonds of phosphoanhydrides. |
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Definition
False; the low-energy bonds require more energy to break, which is why less energy is released when such bonds are hydrolyzed. |
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Term
True/False The term high-energy molecule should be though of as a characteristic of the reaction the molecule is involved in, and not as an intrinsic property of a particular bond within that molecule |
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Definition
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Term
temperature = 25o direct phosphorylation ΔGo'= 3.3 kcal/mol Glucose-6-phosphate- 0.08 mM Pi=1.0mM What minimum concentration of glucose would have to be maintained in a yeast cell for direct phosphorylation to be thermodynamically spontaneos? Is this physiologically reasonable? explain? |
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Definition
ΔG' = ΔGo' + RT ln (glucose-6-phosphate/ glucose*Pi) =3300 + (1.987)(298) ln [(0.08*10-3)/(glucose* 1.10x10-3] =3300 + 592 ln (0.08/ glucose) =3300 + 592 ln (0.08) - 592 ln glucose =3300 - 1495 - 592 ln glucose at equilibrium ΔG'= 0,so ΔG'= 1805-592 ln glucose=0 Because ln glucose = 1805/592 = 3.049, glucose = e3.049 = 21 M This means that a glucose concentration of 21M would be requried just to bring th reaction to equilibrium; anything over this would render the reaction spontaneous in the direction of phosphorylation. This is impossible; even 2M glucose would be a thick syrup |
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Term
ΔGo' =-4.0 Glucose-6-phosphate- 0.08 mM ATP= 1.8mM Pi=1.0mM ADP= 0.15mM What minimum concentration of glucose would have to be maintained in a yeast cell for the coupled reaction to be thermodynamically spontaneous? is this physiologically reasonable? |
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Definition
ΔG'=ΔGo' + RT ln [(Glucose-6-phosphate)(ADP) / (glucose)(ATP) = -4000+(1.987)(298) ln [(.08x10-3)(.15 x10-3)/(glucose)(1.8x10-3)] =-4000+592 ln (6.67x10-6)/glucose = -4000 + 592 ln (6.67x10-6) - 592 ln glucose = -4000 - 7055 - 592 ln glucose= 11055- 592 ln glucose At equilibrium ΔG' = 7.76 x 10-9 M; This means that glucose concentration of 7.76 x 10-9 M would bring the reation to equlibrium; any glucose concentration higher thatn this will render the reaction spontaneous in the direction of phosphorylation. This is physiologicaly very resonable, because glucose phosphorylation is thermodynamically feasible as long as the glucose concentration remains more than 0.01µM |
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Term
Why does ethonol consumption lead to a reduction in NAD+ concentration and to a decrease in aerobic respiration? |
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Definition
| Ethanol catabolism in the body begins with its oxidation(dehydrogenation), with NAD+ as the electron acceptor. The more ethanol that is consumed, the greater the demand for NAD+ and the more serious is the reduction in NAD+ concentration. This means, in turn, that the supply of NAD+ may be inadequate for aerobic respiration of glucose. |
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Term
| Most of the unpleasant effects of hangovers result from an accumulation of acetadehyde and its metabolites. Where does the acetaldehyde come from? |
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Definition
Acetaldehyde is the immediate product of ethanol oxidation: Ethanol+NAD+ →→ acetaldehyde + NAD+ + H+ |
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Term
The medical treatment for methanol poisoning usually involves administration of large doses of ethonol. Why is this treatment effective? |
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Definition
| Methanol and ethanol are both substrates of the enzyme alcohol dehydrogenase and therefore compete for the active site. The body is flooded with a large amount ethanol to provide an effective competitor of methanol, thereby minimizing the production of formaldehyde and lessening the danger that the patient will be "pickled" |
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Term
Why is it not possible to accomplish gluconeogenesis by a simple reversal of all the reaction in glycolysis. |
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Definition
a reaction sequence that is thermodynamically feasible (exergonic) in one direction will not function in the other direction by simple reversal of each of the reactions because it will be endergonic in that direction under the same conditions. |
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Term
| Write an overall reaction for cluconeogenesis that is comparable to reaction 9-16 for glycolysis |
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Definition
| 2 pyruvate + 4 ATP + 2GTP + 6H20 + 2NADH + 2H+ → glucose + 4ADP + 2 GDP = 6Pi + 2NAD+ |
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Term
Assuming concentrations of ATP, ADP, and Pi are such that ΔG' for the hydrolysis of ATP is about -10kcal/mol, what is the approximate ΔG' value for the overall reaction for gluconeogenisis that you wrote in part b? 2 pyruvate + 4 ATP + 2GTP + 6H20 + 2NADH + 2H+ → glucose + 4ADP + 2 GDP = 6Pi + 2NAD+ |
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Definition
| The ΔG' for the glucolytic pathway under typical cellular conditions is about -20 kcal/mol and therefore +20 kcal/mol in the opposite direction. Because four additional phosphoanhydride bonds are hydrolyzed to drive the pathway n the opposite direction and each of those bonds has a ΔG' of about -10 kcal/mol, the net driving force in the gluconeogenic direction is ΔG'= 20+ 4(-10) = -20 kcal/mol |
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Term
| With all of the enzumes for glucolysis and gluconeogenesis present in a liver cell, how does the cell "know" whether it should be synthesizing or catabolizing glucose at any given time? |
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Definition
| The key glycolytic and gluconeogenic enzymes shown in figure 9-12 on p 241 of the text are subject to regulation by a variety of factors, including the AMP, ADP, ATP, acetyl CoA, and F2,6BP status of the cell. Changes int he concentrations of these intermediates either activate or inhibit the regulatory enzumes, thereby effectively turning the pathway "on" in one direction and "Off" in the other. |
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Term
| What experimental evidence most likely led to the discovery that seven of the ten gyloclytic enzymes are localized in an organelle rather that in the cytosol? |
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Definition
| The discovery that glycolytic enzymes are compartementalized in trypanosomes came about as a result of differential centrifugation, a technique that causes most organelles to sediment to the bottom of a centrifuge tube in reponse to centrifufal force while molecules, ions, and smaller organelles such as ribosomes remain in the supernatant. |
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Term
What benefit do you think trypanosomes derive from this compartmentalization of glycolysis? |
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Definition
With the glycolytic enzymes compartmentalized in this way, the enzymes and intermediate in the pathway can be maintained in relatively high concentrations because the organellar volume is small compared to the volume of the cell |
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Term
| What specific transport proteins do you predict are present in the glycosomal membrane? explain |
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Definition
The first seven steps of the glycolytic pathway begin with glucose and lead to the formation of 3-phosphoglycerate. The glycosomal membrane bust therefore have transport proteins for glucose (which moves inward), 3-phoshoglycerate (which moves outward), and inorganic phosphate (which must move inwared to balance the loss of phosphate as 3-phosphoglycerate moves outward). |
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Term
| Glycosomes are usually regarded as a specialized kind of peroxisome. What other enzymes would you therefore expect to find this organelle? explain |
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Definition
| by biochemical definition, a peroxisome is capable of carrying out the generation and degradation of hydrogen peroxide (h2o2) and always possesses at least one h2o2-generating enzyme (an oxidase) and one H2o2-degrading enzyme. |
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Term
In his classic studies of glucose fermentation by yeast cells, Louis Pasteur observed that the rate of glucose consumption by yeast cells was much higher under anaerobic conditions that under aerobic conditions. |
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Definition
| The ATP yield per unit of glucose catabolized is much lower under anaerobic conditions (2ATP/Glucose) than under aerobic conditions (36-38ATP/glucose). A yeast cell funcitoniong under anaerobic conditions must therefore consume 18-19 times as much glucose per unit time as under aerobic condtions in order to sustain the same rate of ATP generation |
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Term
| in 1905, Arthur Harden and William Young found that addition of inorganic phosphate to a yeast extract stimulated and prolonged the fermentation of glucose. |
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Definition
| Although the glycolytic pathway responsible for glucose fermentation by yeast cells begins and ends with an unphosphoarylated molecule (glucose and ethanol, respectively) almost all of hte intermediates in the process are phosphorylated compounds. The fermentation process therefore requires inorganic phosphate, which is taken up in step gly-6 and used to generate ATP and ADP in step gly-7, and will be stimulated by the addition of inorganic phosphate if phosphate is a limiting reagent in the culture medium. |
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Term
An alligator is normally very sluggish, but if provoked is capable of rapidly moving its legs, jaws, and tail. However, such bursts of activity must by followed by long periods of recovery. |
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Definition
| The ATP needed for the rapid but short-term movements of an alligator is generated by glycolysis at the expense of muscle glycogen. The long period of recovery following such movements is needed for the replensishment of muscle glycogen stores. |
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Term
Fermentation of glucose to lactate is an energy-yielding process, although it involves no net oxidation (i.e. even though the oxidation of glyceraldehyde-3-phosphate to glycerate is accompanied by the reduction of pyruvate to lactate and no net accumulation of NADH occurs). |
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Definition
| the oxidation of glyceraldehyde-3-phosphate that occurs at step gly-6 involves the oxidation of a carbonyl group to a carboxylic acid group, which is a highly exergonic reaction. |
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Term
In what sense might arsenate be called an uncoupler of substrate-level phosphorylation? |
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Definition
It allows substrate oxidation to proceed without concomitant ATP generation, releasing this step in the glycolytic pathway from its normal sensitivity to, and regulation by, the availability of ADP and Pi. |
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Term
| Why is arsenate such a toxic substance for an organism that depends critically on glycolysis to meet its energy needs? |
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Definition
| use of aresenate instead of phosphate at step gly-6 results in spontaneous hydrolysis of the arseno intermediate without conservation of the energy of the bonds as ATP. This results in two molecules less of ATP per molecule of glucose, so the energy yield under anaerobic conditions is zero, and the arsenate is therefore fatal. |
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Term
Can you think of other reactions that are likely to be uncoupled by arsenate in the same way as the glyceraldehyde-3-phosphate dehydrogenase reaction? |
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Definition
| Any reaction involving the direct uptake of inorganic phosphate that leads to the generation of a high-energy phosphate bond and the foramtion of ATP may be subject to uncoupling in this way, provided only that the enzyme will accept arsenate in place of phosphate at its active site. |
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Term
| Explain the effect of F2, 6BP on enzyme activity as shown in figure 9-14 a[image] |
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Definition
| Fructose-2, 6BP is an allosteric activatior of phosphofructokinase. The enzyme shows normal Michaelis-Menten kenetics in the presence of F2,6BP but not in its absence. In fact, the apparent Km of the enzyme for fructose-6-phosphate is at least 5 times higher in the absence of F2,6BP than in its absence. |
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Term
Explain the effect of the ATP concentration on the data shown in Figure 9-14b. [image] |
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Definition
| ATP is an alosteric inhibitor of PFK. The enzyme shows normal Michaelis-Menten kinetics when the ATP concentration is low but not when the ATP concentration is high. In fact, the apparent Km of the enzyme for fructose-6-phosphate is at least five times the ATP concentration is low. |
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Term
| What assumptions do you hae to make about the concetration of ATP in Figure 9-14a and about the concentration of F2,6BP in Figure 9-147b? Explain.[image] |
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Definition
| In Figure 9-14a, we must assume that the ATP concentration is high enough to sustain catalytic activity, but still low enough to avoid allosteric inhibition by ATP. |
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Term
Where would you find in the mitochondria Coenzyme A (CoA) |
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Definition
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Term
Where would you find in the mitochondria Coenzyme Q |
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Definition
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Term
Where would you find in the mitochondria Nucleotide Phosphorylation |
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Definition
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Term
Where would you find in the mitochondria succinate dehydrogenase |
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Definition
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Term
Where would you find in the mitochondria Malate dehydrogenase |
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Definition
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Term
Where would you find in the mitochondria Fatty acid elongation |
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Definition
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Term
Where would you find in the mitochondria Dicarboxylate carrier |
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Definition
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Term
Where would you find in the mitochondria Conversion of lactate into pyruvate |
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Definition
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Term
Where would you find in the mitochondria ATP synthas |
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Definition
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Term
Where would you find in the mitochondria aaccumulation of a high proton concentration |
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Definition
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Term
Where would you find in the mitochondria Crista Junction |
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Definition
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Term
Location of molecule and function within the Prokaryotic cell: Coenzyme A |
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Definition
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Term
Location of molecule and function within the Prokaryotic cell: Coenzyme Q |
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Definition
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Term
Location of molecule and function within the Prokaryotic cell: nucleotide phosphorylation |
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Definition
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Term
Location of molecule and function within the Prokaryotic cell: succinate dehydrogenase |
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Definition
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Term
Location of molecule and function within the Prokaryotic cell: malate dehydrogenase |
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Definition
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Term
Location of molecule and function within the Prokaryotic cell: fatty acid elongation |
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Definition
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Term
Location of molecule and function within the Prokaryotic cell: dicarboxylate carrier |
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Definition
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Term
Location of molecule and function within the Prokaryotic cell: conversion of lactate into pyruvate |
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Definition
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Term
Location of molecule and function within the Prokaryotic cell: ATP syntase |
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Definition
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Term
Location of molecule and function within the Prokaryotic cell: accumulation of a high proton concentration |
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Definition
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Term
True/ False The orderly flow of carbon through the TCA cycle is possible because each of the enzymes of the cycle is embedded in the inner mitochondrial membrane in such a manner that their order in the membrane is the same as their sequence in the cycle |
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Definition
False, The orderly flow of carbon through the TCA cycle is possible because most (all but one) of the enzymes of the cycle are present in soluble form inthe mitochondrial matrix |
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Term
True/ False Thermodynamically, acetyl CoA should be capable of driving the phosphoylation of ADP (or GDP), just as succinyl CoA does, assuming availability of the appropriate enzyme. |
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Definition
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Term
True/False Respiration is impossible without oxygen as an electron acceptor for the reoxidation of coenzymes. |
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Definition
False, Respiration is an aerobic process in many organisms because oxygen is the single most common electron acceptor for reoxidation fo reduced coenzymes. However, other electron acceptors such as S, H+, or Fe3+ can be used in the absence of oxygen (anaerobic respiration) |
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Term
True/ False We can predict that the flow of electrons through the electron trasport system is exergonic becuae the NAD/NADH redox pair has a highly negative ΔEo' and the O2/H2O redox pair has a highly positive ΔEo'. |
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Definition
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Term
True/False Unlike NAD, the coenzyme FAD tends to be tightly associated with the dehydrogenase enzyme that use it as an electron acceptor. |
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Definition
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Term
Complete table 10-5 for an aerobic prokaryote, what is the maximum ATP yield? [image] |
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Definition
The maximum ATP yield is obtained by summing the bottom like across the table: ATP yield = 8+6+24= 38 ATP/Glucose [image] |
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Term
Indicate on Table 10-5 the changes that are necessary to calculate the maximum ATP yield for a eukaryotic cell taht uses the glycerol posphate shuttle to move electrons from the cytosol into the matrix of the mitochondria. [image] |
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Definition
| For a eukaryotic cell that uses the glycerol phosphate shuttle, substitute the parenthetical values shown in the Glycolysis column; because the glycerol phosphate shuttle transfers electrons from NADH in the cytosol to FAD in the mitochondrion, the ATP yield per cytoplasmically generated ATP is 2 instead of 3, and the ATP yield is therefore decreased by 2 |
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Term
| Isocitrate dehydrogenase is allosterically activated by ADP |
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Definition
High levels of ADP means low levels of ATP, so it is to the advantage of the cell to activate the metabolic pathway responsible forcoenzyme reduction, which can in turn give rise to ATP synthesis by electron transport |
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Term
| The dehydrogenases that oxidaize isocitrate, α-ketoglurate, and malate are all allosterically inhibited by NADH |
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Definition
High NADH levels mean adequate reduced coenzme for the generation of more ATP, so it makes sense to shut down the catabolic machinery of the cell. |
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Term
| Pyruvate dehydrogenase is allosterically inhibited by ATP |
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Definition
| High ATP levels indicate adequate energy supply, so it makes sense that the enzyme responsible for providing the TCA cycle with more acetyl CoA substrate is shut down. |
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Term
| Phosphofructokinase is allosterically inhibited by citrate. |
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Definition
| High citrate levels are indicative of a sufficient supply of acetyl CoA, so it is reasonable that the key regulatory enzyme of the pathway leading to pyruvate and acetyl CoA is decreased in activity. |
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Term
| Pyruvate dehydrogenase kinase is allosterically activated by NADH |
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Definition
| High levels of NADH mean adequate reduced coenzyme for the generation of ATP, so it makes sense to convert PDH to the inactive form, which is waht PDH kinase does |
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Term
| α-ketoglurate dehydrogenase is allosterically inhibited by succinyl CoA |
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Definition
| High levels of succinyl CoA signal adequate levels of TCA-cycle intermediates, so it seems reasonable to shut down further TCA cycle activity. |
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Term
What happens to the energy that is released as electron transport continues but ATP synthesis causes? Why might it be advantageous for a baby to have thermogenin present in the inner membrane of the mitochondria that are presenet in brown fat tissue? |
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Definition
Given that ATP synthesis does not occur, the energy is lost as heat. For a newborn baby, the heat generated in this way may be vritical to maintenance of body temperature. |
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Term
| some adult mammals also have brown fat. Would you expect to find more brown fat tissue and more thermogenin in a hibernating bear or in a physically active bear? Explain your reasoning. |
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Definition
| One would expect to find more thermogenin in a hibernating bear because the need for additional heat is clearly more critical during hibernation, when the external temperature is likely to be colder and bodily activity much less than in the case of a physically active bear |
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Term
| Given its location in the cell, suggest a mode of action for thermogenin. what kind of ean experiment can you suggest to test your hypothesis? |
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Definition
| The localization of thermogenin to the inner mitochondrial membrane and its mode of action as an uncoupler of electron transport make it likely that thermogenin is a proton translocator that allows electron to move exergonically into the matrix of the mitochondrion jut as Fo does, but without consisting of phospholipid bilayers with and withough thermogenin |
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Term
| What would happen to a mammal if all of its mitochondria were equipped with uncoupling protein, rather than just those in brown fat tissue? |
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Definition
| If all of the mitochondria wer e equipped with uncoupling protein, the mitochondria would not be able to produce much ATP. The organism would therefore have to depend on glycolysis for its ATP synthesis, which would almost certainly not be adequate for an organism that usually depends on mitochondrial ATP synthesis for most of its energy. Furthermore, all of the energy that would normally have gone into ATP synthesis would be liberated as heat so we would end up with an energy-deprived, overheated mammal. |
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Term
| The breakdown of glucose to pyruvate by a cell is an example of a |
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Definition
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Term
| an energy-liberating pathway is also know as |
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Definition
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Term
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Definition
Is broken by hydrolosis has a standard free energy of hydrolosis of -7.3 kcal/mol Is a high-energy bond |
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Term
Which of the following best describes the special high=energy bond of ATP? a) hydrogenation b) phosphoanhydride c) phosphoester d) hydrogen e) ion |
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Definition
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Term
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Definition
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Term
| Which of the following is true of NAD+ |
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Definition
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Term
| Oxidation in biological systems is usually accompanied by |
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Definition
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Term
Which of the following statements best describes the role of NAD+/NADH in glycolosis? a) NADH is used to produce energy by directly creating the phosphoanhydride bonds in ATP b) NADH is capable of pumping ions during glycolosis c) NAD+ is used to carry electrons d) NADH is used primarily in substrate-level phosphoylation |
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Definition
| NAD+ is used to carry electrons |
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Term
| During strenuous exercise, you may notice that your muscle burn. Which of the following statements best explains this phenomenon |
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Definition
| Without oxygen, pyruvate is being converted to lactic acid |
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Term
| The cycle in which lactate is removed from muscle tissue and returned to the liver to produce glucose is called |
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Definition
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Term
| The process of glucose synthesis is called |
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Definition
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Term
| Glucose is transported in the bloodstream to cells in all parts of your body. In body cells, glucose has four main fates |
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Definition
| Glucose is used to synthesize glycogen, is converted to acetyl CoA to make body fat, is catabolized to carbon dioxide and water, and is converted to lactate. |
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