Biochem quizzes - Exam 3 (15-20)

The hydrolysis of a phosphate group from ATP releases 30.5 kj/mol, whereas the hydrolysis of a phosphate from glucose 6-phosphate releases only 13.82 kJ/mol. In that the product is the same, what accounts for the difference? A. ATP has greater resonance stabilization than the product orthophosphate B. Water hydrates ATP greater than glucose 6-phosphate C. ATP has a larger phosphoryl-transfer potential D. There is a greater increase in entropy when ATP is hydrolyzed E. The phosphate ester in ATP is more thermodynamically stable than in glucose 6-phosphate

C. ATP has a larger phosphoryl-transfer potential

The phosphorylation of fructose-6-phosphate is an endergonic reaction with a ΔGoˊ of 16.3 kJ/mol. How do cells overcome this thermodynamic barrier for this reaction under standard conditions? A. The enzyme that catalyzes this reaction couples it with the condensation of ADP and inorganic phosphate, resulting in an overall ΔGoˊ of -46.8 kJ/mol B. This reaction will proceed to the right because the Keq is small C. The enzyme that catalyzes this reaction couples it with the hydrolysis of ATP to ADP and inorganic phosphate, resulting in an overall ΔGoˊ of -14.2 kJ/mol. D. By uncoupling the reaction to the hydrolysis of ATP, the reaction can be driven forward E. This reaction will proceed to the right because the Keq is negative

C. The enzyme that catalyzes this reaction couples it with the hydrolysis of ATP to ADP and inorganic phosphate, resulting in an overall ΔGoˊ of -14.2 kJ/mol.

What are the primary metabolic fates of pyruvate? A. None of the answers given is correct B. ethanol C. ethanol, lactate, and acetyl CoA D. acetyl CoA E. lactate

C. ethanol, lactate, and acetyl CoA

In addition to pyruvate dehydrogenase, what other enzymes are key regulatory sites in the citric acid cycle? A. α-ketoglutarate dehydrogenase B. isocitrate dehydrogenase C. isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and citrate synthase (in bacteria) D. citrate synthase (in bacteria) E. isocitrate dehydrogenase and α-ketoglutarate dehydrogenase

C. isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and citrate synthase (in bacteria)

The major site for gluconeogenesis is in which of the following tissues? A. red blood cells B. brain C. liver D. striated muscle E. adipose

C. liver

What enzyme(s) is (are) responsible for the following reaction? Pyruvate + CoA + NAD+ → acetyl CoA + NADH + H+ + CO2 A. acetyl CoA synthetase and pyruvate decarboxylase B. acetyl CoA synthetase C. pyruvate dehydrogenase complex D. None of the answers given is correct. E. pyruvate decarboxylase

C. pyruvate dehydrogenase complex

Approximately how many ATP or GTP equivalents are produced during one turn of the citric acid cycle? A. 6 B. 1 C. 9 D. 10 E. 12

D. 10

What is substrate-level phosphorylation? A. ATP and AMP synthesis from two molecules of ADP B. phosphorylation of AMP by ATP C. phosphorylation of ATP coupled to an ion gradient D. ATP synthesis when the phosphate donor is a substrate with high-phosphoryl-transfer potential E. phosphorylation of glycolytic intermediates

D. ATP synthesis when the phosphate donor is a substrate with high-phosphoryl-transfer potential

Pyruvate is decarboxylated by which subunit of the PDH? A. E3 B. E4 C. E5 D. E1 E. E2

D. E1

The phosphoryl donor in the formation of phosphoenolpyruvate is: A. inorganic phosphate. B. pyruvate. C. ATP. D. GTP. E. PEP.

D. GTP.

In the Rieske center, the iron-sulfur center is coordinated to the amino acid(s) _______. A. Cys B. Cys and Met C. Met D. His E. His and Cys

D. His

Why does acetyl CoA, a product of fatty acid catabolism, influence the pyruvate dehydrogenase complex (PDH), a control point in carbohydrate catabolism? A. When fatty acid breakdown is high, ADP is low and PDH is inhibited by phosphatase activity. B. When fatty acid breakdown is high, NADH levels drop, causing an increase in E2 activity. C. When fatty acid breakdown is inhibited, PDH is inhibited by acetyl CoA due to phosphatase activity. D. When fatty acid breakdown is high, PDH is inhibited by acetyl CoA due to pyruvate kinase activity. E. When fatty acid breakdown is inhibited, ADP is low, causing a decrease in activity.

D. When fatty acid breakdown is high, PDH is inhibited by acetyl CoA due to pyruvate kinase activity.

Some of the mechanisms by which enzyme catalytic activity is controlled are: A. allosteric control. B. covalent modification. C. allosteric control and covalent modification. D. allosteric control, feedback inhibition, and covalent modification. E. feedback inhibition.

D. allosteric control, feedback inhibition, and covalent modification.

Pyruvate dehydrogenase is _____________ when ATP/ADP ratios are high. A. phosphorylated B. activated C. inhibited and phosphorylated D. inhibited E. activated and phosphorylated

D. inhibited

In which step of the citric acid cycle is FADH2 formed? A. the conversion of malate to oxaloacetate B. All of the answers given are correct. C. the conversion of succinate to malate D. the conversion of succinate to fumarate E. the conversion of succinate to oxaloacetate

D. the conversion of succinate to fumarate

How are the glycolytic enzymes regulated? A. None of the answers given is correct B. through allosteric control C. through transcriptional control D. through transcriptional control, through reversible phosphorylation and through allosteric control E. through reversible phosphorylation

D. through transcriptional control, through reversible phosphorylation and through allosteric control

What is the purpose of phosphorylating glucose in cytosol? A. to trap glucose in the cell B. All of the answers given are correct. C. to convert it to a more soluble form D. to trap glucose in the cell and to destabilize glucose and facilitate the next series of metabolic steps E. to destabilize glucose and facilitate the next series of metabolic steps

D. to trap glucose in the cell and to destabilize glucose and facilitate the next series of metabolic steps

Electron flow down the electron-transport chain leads to the: A. a dangerous imbalance of K+ ions across the mitochondiral membrane. B. None of the answers given is correct. C. transport of protons across the inner mitochondrial membrane from the intermembrane space into the matrix. D. transport of protons across the inner mitochondrial membrane from inside the matrix to the intermembrane space. E. coupled synthesis of GTP.

D. transport of protons across the inner mitochondrial membrane from inside the matrix to the intermembrane space.

What pathologic condition(s) results from free-radical injury? A. Parkinson's disease B. emphysema C. atherogenesis D. diabetes E. All of the answers given are correct.

E. All of the answers given are correct.

What is the rationale for saying that "electrons flow down the electron-transport chain"? A. Electrons flow from the outer surface to the inner surface, a top down perception. B. Electrons flow from half-reactions with more positive redox potentials to more negative. C. Electrons flow from oxidized carriers to reduced carriers in discrete steps like a staircase. D. Because we think of electrons flowing like a liquid, the only direction electrons can flow is down. E. Electrons flow from reactions that continuously generate negative free energy values.

E. Electrons flow from reactions that continuously generate negative free energy values.

What evidence is there that modern mitochondria are the result of a single ancient event? What is the event called? A. Modern mitochondria have specific transcription and translation machinery similar to viruses: viral endosymbiosis event. B. Modern mitochondria have DNA polymerase sequences similar to a single bacteria: replication event. C. Modern mitochondria are the only organelles in the cell with a double membrane: electron-transfer event. D. None of the answers given is correct. E. Modern mitochondria have circular DNA similar to bacteria: endosymbiotic event.

E. Modern mitochondria have circular DNA similar to bacteria: endosymbiotic event.

Electron carrier(s) that include ATP are: A. FMN and FAD B. FAD C. FMN D. NAD+ E. NAD+ and FAD

E. NAD+ and FAD

Choose the correct path taken by a pair of electrons as they travel down the electron-transport chain. A. FADH2 → Complex I → CoQ → Complex III → Cyt c → Complex IV → O2 B. FADH2 → Complex II → CoQ → Complex III → Cyt c → Complex IV → O2 C. NADH → Complex I → CoQ → Complex III → Cyt c → Complex IV → O2 D. NADH → Complex I → Complex II→ Complex III → Cyt c → Complex IV → O2 E. Two of the answers given are correct.

E. Two of the answers given are correct. C. NADH → Complex I → CoQ → Complex III → cytochrome c → Complex IV → O₂ and B. FADH2 → Complex II → CoQ → Complex III → Cytochrome c → Complex IV → O₂

Which of the following intermediates is needed for the conversion of galactose into glucose by reacting with galactose 1-phosphate? A. glucose 6-phosphate B. UDP-galactose C. fructose 6-phosphate D. glucose 1-phosphate E. UDP-glucose

E. UDP-glucose

What molecule initiates the citric acid cycle by reacting with oxaloacetate? A. Citrate B. pyruvate C. All of the answers given are correct. D. oxaloacetate E. acetyl CoA

E. acetyl CoA

The metabolic pathways that require energy and are often biosynthetic processes are: A. All of the answers given are correct. B. ametabolic. C. catabolic. D. None of the answers given is correct E. anabolic.

E. anabolic.

Beriberi symptoms are similar to those of which disease? A. type II diabetes B. cancer C. lactic acidosis D. scurvy E. arsenite poisoning

E. arsenite poisoning

Formation of citrate from acetyl CoA and oxaloacetate is a(n) _________ reaction. A. reduction B. ligation C. hydration D. oxidation E. condensation

E. condensation

Lactate produced in muscle tissue is converted to _________ by __________ . A. pyruvate; glycolysis B. ATP; the Krebs cycle C. lactate; the Cori cycle D. glucose; gluconeogenesis E. glucose; the Cori cycle

E. glucose; the Cori cycle

Which of the following functions as a "flexible swinging arm" when it transfers the reaction intermediate from one active site to the next? A. coenzyme A B. thiamine pyrophosphate C. FAD D. NAD+ E. lipoamide

E. lipoamide

What type of enzyme catalyzes the intramolecular shift of a chemical group? A. hydrolase B. ligase C. kinase D. dehydrogenase E. mutase

E. mutase

Which energy source is used to regenerate ATP from ADP and Pi? A. reduction of pyruvate to lactate. B. None of the answers given is correct. C. All of the answers given are correct. D. electrochemical potential of stored glycogen. E. oxidation of carbon to CO2.

E. oxidation of carbon to CO2.

How many high-energy phosphate bonds are consumed in gluconeogenesis? A. three B. ten C. two D. four E. six

E. six

Fermentation occurs in the absence of oxygen, but O2 is not found in any of the reactions of glycolysis or fermentation. So, what drives these reactions at the level of glycolysis and fermentation? A. ATP is synthesized in glycolysis, only if NAD+ is regenerated during fermentation B. Pyruvate donates electrons to NADH in lactic acid fermentation C. In the formation of ethanol, pyruvate is decarboxylated in a reversible reaction, once oxygen is present again D. NADH synthesized in glycolysis is used to oxidize pyruvate to acetyl CoA during fermentation reactions E. In the formation of ethanol, acetaldehyde accepts electrons from NADH, regenerating NAD+

A. ATP is synthesized in glycolysis, only if NAD+ is regenerated during fermentation

Biotin provides __________ for the pyruvate carboxylase reaction. A. All of the answers given are correct. B. a long flexible arm for active site location of substrate C. carboxylation of pyruvate D. None of the answers given is correct E. group transfer from one site of the enzyme to another

A. All of the answers given are correct.

High levels of ATP and citrate ___________. A. All of the answers given are correct. B. indicate remote gluconeogenesis. C. None of the answers given is correct. D. inhibit glycolysis. E. indicate a high energy-well fed state.

A. All of the answers given are correct.

Which of the following are reasons that glucose is a common metabolic fuel used by living organisms? A. It has a stable ring structure and is unlikely to glycosylate proteins and it has been found as one of the monosaccharides formed under prebiotic conditions B. It has a stable ring structure and is unlikely to glycosylate proteins C. it has been found as one of the monosaccharides formed under prebiotic conditions D. It is the only sugar used by the brain

A. It has a stable ring structure and is unlikely to glycosylate proteins and it has been found as one of the monosaccharides formed under prebiotic conditions

Although we study the citric acid cycle as the final stage oxidation of carbon from glucose, an in-depth look at the cycle shows intermediates entering and leaving the cycle from a number of metabolic pathways. With all of these demands on the cycle, how does it maintain a minimal level of oxaloacetate (OAA) to allow the cycle to function? A. OAA is synthesized via pyruvate carboxylase in an anapleurotic reaction that occurs when acetyl CoA is present. B. Isocitrate dehydrogenase is allosterically inhibited by ADP, which signifies the need for more energy. C. OAA can be formed by the condensation of two moles of acetyl CoA and occurs when the energy charge of the cell is high. D. The rate of the cycle is increased when the cell has high levels of NADH. E. OAA is formed directly via the deamination of glutamate.

A. OAA is synthesized via pyruvate carboxylase in an anapleurotic reaction that occurs when acetyl CoA is present.

In general the liver_______________. A. all of the answers given are correct B. will not utilize glucose under starvation/low energy conditions C. acts as a glucose buffer for the rest of the body D. is a producer of glucose for the body under low energy conditions E. None of the answers given is correct

A. all of the answers given are correct

Which is the correct coenzyme-carrier pair? A. coenzyme A: acyl. B. tetrahydrofolate: electrons. C. NADH: acyl. D. lipoamide: aldehyde. E. thiamine pyrophosphate: glucose.

A. coenzyme A: acyl.

Which two 3-carbon molecules are generated by the cleavage of fructose-1,6-bisphosphate? A. glyceraldehyde-3-phosphate and dihydroxyacetone phosphate B. glyceraldehyde-3-phosphate and 3-phosphoglycerate C. glyceraldehyde-3-phosphate and pyruvate D. pyruvate and phosphoenolpyruvate E. enolase and 2-phosphoglycerate

A. glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

Which of the following is the ultimate electron acceptor in aerobic organisms? A. oxygen B. succinate C. carbon dioxide D. FAD E. NAD+

A. oxygen

Which of the following molecules has a higher phosphoryl-transfer potential than ATP? A. phosphoenolpyruvate, creatine phosphate, and 1,3-bisphosphoglycerate. B. creatine phosphate. C. 1,3-bisphosphoglycerate and creatine phosphate. D. 1,3-bisphosphoglycerate. E. phosphoenolpyruvate.

A. phosphoenolpyruvate, creatine phosphate, and 1,3-bisphosphoglycerate.

Which of the following vitamins are precursors to coenzymes that are necessary for the formation of acetyl CoA from pyruvate? A. thiamine, riboflavin, niacin, lipoic acid, and pantothenic acid B. thiamine, riboflavin, niacin, and biotin C. thiamine, riboflavin, niacin, lipoic acid, pantothenic acid, and biotin D. thiamine, riboflavin, and lipoic acid E. None of the answers given is correct.

A. thiamine, riboflavin, niacin, lipoic acid, and pantothenic acid

Which of the following vitamins are precursors to coenzymes that are necessary for the formation of succinyl CoA from α-ketoglutarate? A. thiamine, riboflavin, niacin, lipoic acid, and pantothenic acid B. thiamine, riboflavin, and lipoic acid C. thiamine, riboflavin, niacin, and biotin D. thiamine, riboflavin, niacin, lipoic acid, pantothenic acid, and biotin E. None of the answers given is correct.

A. thiamine, riboflavin, niacin, lipoic acid, and pantothenic acid

Which of the following does not pump protons? A. Complex IV B. Complex II C. Complex III D. Complex I E. All of the answers given are correct.

B. Complex II

Which of the following must be regenerated for glycolysis to proceed? A. pyruvate B. NAD+ C. ATP D. UDP-glucose E. All of the answers given are correct.

B. NAD+

Which of the following does not participate in, nor is a component of, the electron-transport chain? A. cytochrome c1 B. coenzyme A C. NADH D. coenzyme Q E. non-heme, iron-sulfur proteins

B. coenzyme A

What are the steps involved (in order) in the conversion of pyruvate to acetyl CoA? A. oxidation, transfer to CoA, decarboxylation B. decarboxylation, oxidation, transfer to CoA C. None of the answers given is correct. D. decarboxylation, transfer to CoA, oxidation E. oxidation, decarboxylation, transfer to CoA

B. decarboxylation, oxidation, transfer to CoA

High blood sugar after a meal _______ the level of insulin released by the pancreas A. chronically inhibits B. increases C. has no effect on D. chronically activates E. decreases

B. increases

The primary raw materials for gluconeogenesis are: A. fructose and glycerol. B. lactate and amino acids. C. lactose and lactate. D. galactose and sucrose. E. pyruvate and oxaloacetate.

B. lactate and amino acids.

The bifunctional enzyme is also known as __________. A. protein kinase 2 B. phosphofructokinase II C. fructose 1-6 phosphatase D. phosphofructokinase I E. phosphoenolpyruvate carboxy kinase

B. phosphofructokinase II

The direct movement of substrates from one enzyme to the next is called _________. A. cell with sufficient available water B. substrate channeling C. protein complex D. linker coenzyme E. electron acceptor

B. substrate channeling

In muscle, the enzyme that catalyzes a substrate level phosphorylation is: A. ATP-GTP transferase B. succinyl CoA synthetase C. GTP kinase D. protein kinase C E. nucloside triphosphate transferase

B. succinyl CoA synthetase

What is the standard-state free energy (ΔG°′) for the hydrolysis of ATP to ADP? A. −45.6 kJ/mol B. −30.5 kJ/mol C. +45.6 kJ/mol D. +30.5 kJ/mol E. −14.6 kJ/mol

B. −30.5 kJ/mol