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BioChem McN
Accumulation of quizzes and homeworks
| Question | Answer |
|---|---|
| Which organ produces the most digestive enzymes? | Pancreas |
| Which metabolic process breaks down nutrients? | Catabolism |
| Under standard conditions, which reactions would proceed forward? | deltaG = 0 & deltaG = negative value |
| The deltaGo' is the only factor that determines whether a reaction will proceed forward in the cell. | False |
| What is the net charge of ATP? | -4 |
| Differentiate between anabolism and catabolism. | Anabolism creates and catabolism breaks down-- both are metabolic pathways. Anabolism creates molecules from smaller units. Catabolism breaks down molecules into smaller units. |
| Describe the ATP-ADP cycle and its role in biological systems | The ATP-ADP cycle allows for the storage and release of energy. A breakdown of this cycle is that it allows for systems to create their own energy from ATP. Numerous systems also use this cycle as a means of storage and release-- including glycolysis |
| "When a system is in equilibrium, the Gibbs free energy is maximum" You are disgusted, not only at the vandalism but at the ignorance of the vandal. Why? | I would just explain that what was written was incorrect-- when a system is in equilibrium, the Gibbs free energy is minimum; not maximum. |
| Why bother to eat? What are three primary uses for cellular energy? | Eating gives us the energy to function regularly as our bodies break down glucose and use it. It is needed for nutrients. 3 primary uses are biosynthetic reactions, active transport, & cellular movements & the performance of mechanical work. |
| What is true for a muscle performing lactic acid fermentation? | The process is inhibited by ATP & The process is exergonic |
| The gross yield of ATP from the metabolism of glucose to pyruvate is four molecules of ATP. However, the net yield of ATP from this metabolism is only two molecules of ATP. Why are the gross and net values different? | They are different because two molecules of ATP are required in order to convert glucose into fructose 1,6-biphosphate. So, four molecules of ATP were initially produced, but two of them were needed for conversion of glucose to fructose 1,6-biphosphate. |
| Lactic acid fermentation and alcohol fermentation are oxidation-reduction reactions. Identify the ultimate electron donor and electron acceptor. | In lactic acid fermentation, the electron donor is glyceraldehyde 3-phosphate and the electron acceptor is pyruvate. In alcohol fermentation, the electron donor is glyceraldehyde 3-phosphate and the electron acceptor is acetaldehyde. |
| Glucose 6-phosphate is processed by glycolysis to lactate. How much net ATP is generated? | 3 ATP |
| Dihydroxyacetone phosphate is processed by glycolysis to lactate. How much net ATP is generated? | 2 ATP |
| Glyceraldehyde 3 phosphate is processed by glycolysis to lactate. How much net ATP is generated? | 2 ATP |
| Fructose is processed by glycolysis to lactate. How much net ATP is generated? | 2 ATP |
| Sucrose is processed by glycolysis to lactate. How much net ATP is generated? | 4 ATP |
| The recommended daily allowance for the vitamin niacin is 15 mg per day. How would glycolysis be affected by niacin deficiency? | Glycolysis would be affected by niacin deficiency where the step in which glycolaldehyde 3-phosphate is being converted to 1,3-biphosphate glyceride would be impaired. |
| Although both hexokinase and phosphofructokinase catalyze irreversible steps in glycolysis and the hexokinase-catalyzed step is first, phosphofructokinase is the pacemaker. What is the fate of the glucose 6-phosphate formed by hexokinase? | This question is a bit confusing but I believe the fate of glucose 6-phosphate would be to converted into glycogen in order to be used as energy storage. |
| Why can't the reactions of the glycolytic pathway simply be run in reverse to synthesize glucose? | The glycolytic pathway cannot be run in reverse to synthesize glucose because it would be too difficult to climb the three high energy steps that would needed to be overcome if the pathway was attempted to be run in reverse. |
| Why is it in the muscle's best interest to export lactic acid into the blood during intense exercise? | It is in the muscle's best interest to export lactic acid into the blood because if it stayed in the cell, the cell's pH would fall and lead to denaturation of muscle protein. |
| What is the equilibrium concentration of fructose 1,6-bisphosphate when 1 mM of fructose 1,6-bisphosphate is incubated with aldolase under standard conditions? | The equilibrium concentration of fructose 1,6-bisphosphate is 7.8 x 10^-4 M |
| What is the equilibrium concentration of dihydroxyacetone phosphate when 1 mM of fructose 1,6-bisphosphate is incubated with aldolase under standard conditions? | The equilibrium concentration of dihydroxyacetone phosphate is 2.2 x 10^-4 M |
| What is the equilibrium concentration of glyceraldehyde 3-phosphate when 1 mM of fructose 1,6-bisphosphate is incubated with aldolase under standard conditions? | The equilibrium concentration of glyceraldehyde 3-phosphate is 2.2 x 10^-4 M |
| The intravenous infusion of fructose into healthy volunteers leads to a 2-5-fold increase in lactate in blood, far greater increase than observed after infusion of glucose. a. Why is glycolysis more rapid after the infusion of glucose? | a) Glycolysis is more rapid after the infusion of glucose because it would bypass the control of phosphofructokinase. |
| The intravenous infusion of fructose into healthy volunteers leads to a 2-5-fold increase in lactate in blood, far greater increase than observed after infusion of glucose. b. Fructose has been used instead of glucose. Why is this use of fructose unwise? | b) PFK would be bypassed by the fructose pathway which could lead to excess fat and cause glycolysis to become unregulated. |
| What is glucose directly converted to in the glycolysis pathway? | glucose 6-phosphate |
| What is 2-phosphoglycerate directly converted to in the glycolysis pathway? | phosphoenolpyruvate |
| What is dihydroxyacetone phosphate directly converted to in the glycolysis pathway? | glyceraldehyde 3-phosphate |
| Which enzyme uses phosphoenolpyruvate as a substrate in glycolysis? | Pyruvate Kinase |
| Which enzyme uses fructose 1,6-phosphate as a substrate in glycolysis? | Aldolase |
| Which enzyme converts glucose to glucose-6-phosphate in glycolysis? | Hexokinase |
| What is glucose 6-phosphate directly converted to in the glycolysis pathway? | fructose 6-phosphate |
| Which enzyme uses 1,3-bisphosphoglycerate as a substrate in glycolysis? | Phosphoglycerate Kinase |
| How many steps are there in glycolysis? | 10 |
| Which enzyme uses 2-phosphoglycerate as a substrate in glycolysis? | Enolase |
| Which enzyme uses dihydroxyacetonephosphate as a substrate in glycolysis? | Triose Phosphate Isomerase |
| One turn of the citric acid cycle generates _____. | 1 GTP, 3 NADH, 1 FADH2 |
| If acetyl-CoA labeled with 14C, as shown in the figure to the right, were used as the substrate for the citric acid cycle, which of the following intermediates would be produced during the first round of the cycle? **McNulty HW 2 | **McNulty HW 2 |
| Aconitase catalyzes the _____ of citrate, followed by a _____ reaction. | dehydration; hydration |
| Which enzyme catalyzes a reaction most like that catalyzed by a-ketoglutarate dehydrogenase? | pyruvate dehydrogenase |
| Which of the following enzymes catalyzes a substrate-level phosphorylation? | succinyl-CoA synthetase |
| Which reaction below produces GTP in the citric acid cycle? | succinyl CoA --> succinate |
| How does the reaction catalyzed by malate dehydrogenase proceed despite a Delta-G°' of 29.7 kJ/mol? | Concentrations of oxaloacetate are kept very low by rapid use in the subsequent step. |
| An individual with a shortage of B vitamins (which include thiamine and riboflavin) may feel fatigued because of decreased pyruvate dehydrogenase activity. Which of the following would be true regarding this shortage? | The amount of acetyl CoA produced from carbohydrate metabolism that enters the citric acid cycle would be decreased. |
| In the electron transport chain, electrons are passed from redox center to redox center ____. | spontaneously because of the redox potential gradient |
| Complexes I and II each transfer electrons to ______. | ubiquinone |
| How many protons are transported from the matrix to the intermembrane space by Complex I? | 4 |
| A poison that prevents the transfer of electrons from the last [Fe-S] cluster of Complex I to coenzyme Q is added to a suspension of actively respiring mitochondria. Which of the following will be observed? | ATP production would be reduced because of a decrease in the number of protons pumped out of the mitochondrial matrix. |
| Gluconeogenesis is the reverse of glycolysis - except for ________ steps (how many steps are different)? | 3 |
| What is the storage form of glucose within the cell? | glycogen |
| Which of the following are electron carriers? | NADH & FADH2 |
| Where are oxidative phosphorylation proteins found? | embedded the inner membrane of the mitochondria |
| What is the fate of carbons that enter the citric acid cycle? | CO2 |
| The structure of ATP synthase changes in conformation because of _____. | the rotation of the gamma subunit |
| Complex IV uses _____ and _____ ions to reduce oxygen to water. | copper; iron |
| Complex III accepts electrons from _____ and transfers them to _____. | ubiquinol; cytochrome c |
| Which predominant form of fat is stored in adipose tissue | triacylglycerides |
| After covalent attachment to CoA, the next step of fatty acid degradation is: | oxidation |
| Each cycle of beta-oxidation removes: | 2 Carbons |
| The first step of fatty acid biosynthesis is the synthesis of: | malonyl-CoA |
| In protein degradation, amino acid nitrogen is converted to: | urea |
| A low-carbohydrate diet proclaims that, without glucose, adipose tissue is unable to store triacylglycerol? | This is somewhat TRUE. Adipose tissue synthesizes the triacylglycerol it stores from fatty acids obtained from chylomicra and VLDL and esterifies these to glycerol phosphate, which is typically obtained in a side reaction of glycolysis. |
| Each round of b-oxidation of a saturated fatty acyl-CoA produces _____. | 1 NADH, 1 FADH2, 1 acetyl-CoA |
| What are the b-oxidation products of stearic acid, a saturated fatty acid with 18 carbons? | 8 NADH, 8 FADH2, 9 acetyl-CoA |
| How many ATP can be produced by the complete oxidation of palmitoleic acid, a 16-carbon monounsaturated fatty acid, considering that the fatty acid must first be activated? | 104.5 |
| If a reaction that included all of the enzymes involved in fatty acid synthesis was supplied with excess ATP, NADPH, acetyl-CoA, and 14CO2 (where the carbon was a 14C-label), where would the labeled carbon appear in the finished fatty acid? | no carbons would be labeled |
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