Quizzes

What product of the preparatory phase of glycolysis is required in the payoff phase, but at twice the amount? A. Dihydroxyacetone phosphate B. Pyruvate C. NAD^+ D. ADP E. Phosphate

ADP

Group transfer reactions from ATP are common in biochemistry. What is the soluble product from pyrophosphorylation from ATP? A. inorganic phosphate B. pyrophosphate C. AMP D. ADP E. cAMP

AMP

All of the following characterize phosphofructokinase-1 (PFK-1) EXCEPT: A. One of the important regulatory sistes in glycolysis B. ATP increases the affinity of the enzyme for fructose-6-phosphate C. PFK-1 activity is regulated by the energy level of the cell D. AMP decreases the Km of PFK-1 for fructose-6-phosphate. E. the subunits of PFK-1 behave allosterically when bind to regulators

ATP increases the affinity of the enzyme for fructose-6-phosphate

Enzyme control is accomplished in which of the following ways? A. Genetic Control B. Covalent modification C. Allosteric regulation D. Compartmentation E. All of the above are correct

All of the above are correct

Which of the following is TRUE about gluconeogenesis? A. In mammals, gluconeogenesis occurs predominately in the muscle. B. Gluconeogenesis is the pathway by which glucose is converted to glycogen C. The gluconeogenesis pathway is the glycolysis pathway running in the opposite direction. D. Pants do not undergo gluconeogenesis. E. All of the bypass reactions used in gluconeogenesis are irreversible

All of the bypass reactions used in gluconeogenesis are irreversible

All describe biochemical (also called modified) standard state for a thermodynamic parameter EXCEPT: A) designated with a prime (') symbol B) H+ ion of 1M C) 1 M for solutions D) 1 atm for gases E) When the solvent is water at pH = 7

H+ ion of 1 M

A recently reported mutase may generate an intermediate having a free radical. If you studied this reaction, which of the following would you look for in the mechanism that would be characteristic of other mutase reactions? A. Nucleophilic attack on a carbonyl carbon B. A ring in a prosthetic group that could undergo resonance stabilization C. An SN1 substitution D. A requirement for O2 E. Homeolytic cleavage of a covalent bond

Homeolytic cleavage of a covalent bond

Which of the following is TRUE of metabolism? A) Degradative reactions require a net input of energy B) Synthetic pathways are anabolic C) Catabolism and anabolism are linked by O2 D) Catabolic reactions require the breakdown of ATP, and anabolic reactions generate ATP E) None of the above

Synthetic pathways are anabolic

The ultimate electron acceptor in the fermentation of glucose to ethanol is: A. acetaldehyde B. acetate C. ethanol D. NAD+ E. pyruvate

acetaldehyde

During glycolysis, glucose 1-phosphate is converted to fructose 6-phosphate in two successive reactions: glucose 1-phosphate --> glucose 6-phosphate ΔG'° = -7.1 kJ/mol glucose 6-phosphate --> fructose 6-phosphate ΔG'° = +1.7 kJ/mol ΔG'° for the following overall reaction is: fructose 6-phosphate --> Glucose 1-phosphate, ΔG'° = _____? A) -8.8 kJ/mol. B) -7.1 kJ/mol. C) -5.4 kJ/mol. D) +5.4 kJ/mol. E) +8.8 kJ/mol.

+5.4 kJ/mol

The anaerobic conversion of 1 mol of glucose to 2 mol of lactate by fermentation is accompanied by a net gain of: A. 1 mol of ATP B. 1 mol of NADH C. 2 mol of ATP D. 2 mol of NADH E. None of the above

2 mol of ATP

While you have learned in many classes that ATP hydrolysis powers reactions in cells, this is not the case! What is the most common biochemical role of ATP? A. To induce a conformational change in a protein B. To release energy that can be captured for an associated reaction C. A source for the transfer of part of the ATP to another molecule, a group transfer D. To donate a phosphate group to a chemical reaction E. To increase the total free energy of the products of a reaction over the reactants

A source for the transfer of part of the ATP to another molecule, a group transfer

How can thermodynamically unfavorable reactions such as the synthesis of DNA and protein polymers, occur in cells? A. Cells couple thermodynamically unfavorable reactions to reactions that result in a positive change in enthalpy. B. Cells couple thermodynamically unfavorable reactions to the hydrolysis of ATP. C. Cells couple thermodynamically unfavorable reactions to reactions that have a positive free energy. D. Cells couple thermodynamically unfavorable reactions to reactions that result in a decrease in entropy. E. None of the above.

Cells couple thermodynamically unfavorable reactions to the hydrolysis of ATP

Which one of the following directly results in the activation of glycogen synthase? A. Binding of glucose-6-phosphate B. Dephosphorylation of multiple residues by phosphoprotein phosphorylase-1 (PP1) C. Phosphorylation of specific residues by casein kinase II (CKII) D. Phosphorylation of specific residues by glycogen synthase kinase-3 (GSK-3) E. The presence of insulin

Dephosphorylation of multiple residues by phosphoprotein phosphorylase-1 (PP1)

For the first five steps of glycolysis, the appropriate sequence of enzymes is: I. phophofructokinase-1 (PFK-1) II. hexokinase III. aldolase IV. phophohexose isomerase V. triose phosphate isomerase A. I, III, II, V, IV, B. II, III, IV, V, I C. II, IV, I, III, V D. II, IV, V, III, I E. IV, II, I, III, V

II, IV, I, III, V

The oxidation-reduction reaction Fe2+ + Cu2+ ↔ Fe3+ + Cu+, can be described in terms of two half-reactions: (1) Fe2+ ↔ Fe3+ + e- (2) Cu2+ + e- ↔ Cu+ Which of the following statements is true? A. In the overall reaction at the top, the cupric ion (Cu2+) is the reducing agent. B. In half-reaction (2), cupric ion (Cu2+) is being oxidized. C. In half-reaction (1), Fe3+ and e- constitute a conjugate redox pair. D. In the overall reaction at the top, the ferrous ion (Fe2+) is oxidized by the cupric ion (Cu2+). E. None of the above.

In the overall reaction at the top, the cupric ion (Cu2+) is the reducing agent.

Which of the following would be an inappropriate biochemical response to low blood sugar? A. Increase gluconeogenesis B. Increase pentose phosphate, nonoxidative phase. C. Increase formation of glycogen D. Inhibit glycolysis E. Increase pentose phosphate, oxidative phase

Increase pentose phosphate, oxidative phase

The reaction below belongs to which type of reaction? (Lecture 1) A. Reactions that make or break carbon-carbon bonds B. Isomerizations and eliminations C. Free-radical reactions D. Group transfers E. Oxidation-reductions

Isomerizations and eliminations

Which of the following is TRUE about fructose 2,6-bisphosphate in the liver? A. It inhibits glycolysis. B. It inhibits gluconeogensis C. It inhibits phosphofructokinase-1 (PFK-1) D. It stimulates fructose 1,6-bisphasphatase-1 (FBPase-1). E. None of the above.

It inhibits

Which of the following sugars could be transformed into fructose 6-phosphates were no longer available (eg. Glucose and Glucose phosphates are depleted by pentose phosphate pathway)? A. Galactose B. Trehalose C. Lactose D. Amylose E. Mannose

Mannose

PEP and 2_PG have similar amounts of potential metabolic energy with respect to decomposition to Pi, CO2 and H2O, but the enolase reaction: A. creates a much more unstable reactive intermediate B. rearranges 2-PG into a form from which more potential energy can be released by hydrolysis C. rearranges 2-PG to a form with greater binding potential to the enzyme D. changes the delta G to the reaction to increase the potential energy E. none are true

Rearranges 2-PG into a form from which more potential energy can be released by hydrolysis

Which of the following statements about gluconeogenesis in animal cells is true? A. A rise in the cellular level of fructose-2,6-bisphosphate stimulates the rate of gluconeogenesis. B. An animal fed a large excess of fat in the diet will convert any fat not needed for energy production into glycogen to be stored for later use. C. The conversion of fructose 1,6-bisphosphate to fructose 6- phosphate is not catalyzed by phosphofructokinase-1, the enzyme involved in glycolysis. D. The conversion of glucose 6-phosphate to glucose is catalyzed by hexokinase, the same enzyme involved in glycolysis. E. The conversion of phosphoenol pyruvate to 2- phosphoglycerate occurs in two steps, including a carboxylation.

The conversion of fructose 1,6-bisphosphate to fructose 6- phosphate is not catalyzed by phosphofructokinase-1, the enzyme involved in glycolysis.

Which of the following is true about isozymes? A. They have the same amino acid sequence. B. They have the same kinetic properties. C. They catalyze the same reaction. D. They cannot be expressed in the same cell at the same time E. None of the above

They catalyze the same reaction

Which one of the following compounds does not have a large negative free energy of hydrolysis? A. 1,3-bis phosphoglycerate B. 3-phosphoglycerate C. ADP D. Phosphoenolpyruvate E. Thioesters (e.g. acetyl-CoA)

Thioesters

When a muscle is stimulated to contract aerobically, less lactic acid is formed than when it contracts anaerobically because: A. glycolysis does not occur to significant extent under aerobic conditions B. muscle is metabolically less active under aerobic than anaerobic conditions C. the lactic acid generated is rapidly incorporated into lipids under aerobic conditions D. under aerobic conditions in muscle, the major energy-yielding pathway is the pentose phosphate pathway, which does not produce lactate E. under aerobic conditions most of the pyruvate generated as a result of glycolys is oxidized by the citric acid cycle rather than reduced to lactate

Under aerobic conditions most of the pyruvate generated as a result of glycolysis is oxidized by the citric acid cycle rather than reduced to lactate

In glycolysis, fructose 1,6-bisphosphate is converted to two products with a standard free-energy change (ΔG'°) of 23.8 kJ/mol. Under what conditions (encountered in a normal cell) will the free-energy change (ΔG) be negative, enabling the reaction to proceed to the right? A) If the concentrations of the two products are high relative to that of fructose 1,6-bisphosphate. B) The reaction will not go to the right spontaneously under any conditions because the ΔG'° is positive. C) Under standard conditions, enough energy is released to drive the reaction to the right. D) When there is a high concentration of fructose 1,6- bisphosphate relative to the concentration of products. E) When there is a high concentration of products relative to the concentration of fructose 1,6-bisphosphate.

When there is a high concentration of fructose 1,6- bisphosphate relative to the concentration of products.

Which of the following statements regarding ATP is true? A. the energy of hydrolysis is the same for all of the phosphate groups of the molecule B. despite the very exergonic nature of hydrolysis ATP does not hydrolyze spontaneously due to a very high activation energy C. the delta G of hydrolysis within the cell is substantially greater than the delta G' knot due to a higher concentration of ATP with respect to ADP D.electrostatic attraction of the phosphate groups contributes to a more exergonic free energy\ E. both B and C are correct

despite the very exergonic nature of the hydrolysis, ATP does not hydrolyze spontaneously due to a very high activation energy

Living cells and organisms A) exchange energy but not matter with their surroundings B) exchange energy and material with their surroundings C) are closed systems D) are at equilibrium with their surroundings E) None of the above

exchange energy and material with their surroundings.

Glycolysis is the name given to a metabolic pathway occurring in may different cell types. It consists of 11 enzymatic steps that convert glucose to lactic acid. Glycolysis is an example of: A. aerobic metabolism B. anabolic metabolism C. a net reductive process D. fermentation E. oxidative phosphorylation

fermentation

Each of the following is a true statement EXCEPT: A. standard free energy change for a redox reaction is related to the standard cell potential B. standard free energy change for a redox reaction is related to the number of electrons transferred C. for redox reactions with negative standard cell potential stanard free energy change is negative D. redox reactions must occur in pairs, where the total number involved in the reduction E. all are true statements

for redox reactions with negative standard cell potentials, standard free energy change is negative

In the second half of the glycolytic pathway, _____ ATP molecules are produced and with the offset of ____ ATPs consumed in the first half, the net yield is ______ ATPs and ______ NADH per glucose. A. four; four; zero; two; B. four; two; two; two; C. two; two; four; one; D. two; one; one; one; E. four; one; three; one;

four, two, two, two

The primary REGULATORY point of gluconeogenesis is __________. A. glucose-6-phosphatase B. fructose-1,6-bisphosphatase C. fructose-2,6-bisphosphatase D. pyruvate carboxylase E. PEP carboxykinase

fructose-1,6-bisphosphatase

Which of the following reactions represents of the gluconeogenic reversal of PFK-1 in glycolysis? A. fructose-6-P + ADP --> fructose + ATP B. fructose-6-P + H2O --> fructose + Pi C. fructose-1,6-bisphosphate + ADP --> fructose-6-P + Pi D. fructose-1,6-bisphosphate + H2O --> fructose-6-P + Pi E. none of the above

fructose-1,6-bisphosphate + H2O --> fructose-6-P + Pi

All of the following contribute to the large, negative, free-energy change upon hydrolysis of ATP except: A. electrostatic repulsion in the reactant. B. low activation energy of forward reaction. C. stabilization of products by extra resonance forms. D. stabilization of products by ionization. E. stabilization of products by solvation.

low activation energy of forward reaction

Glucose labeled with 14^C in C-1 and C-6 gives rise in glycolysis to pyruvate labeled in: A) its methyl carbon B) its carbonyl carbon C) its carboxyl carbon D) A and C E) all three carbons

methyl carbon

Compounds with a large ______ reduction potential have a strong tendency to undergo oxidation, and as such, NADH is a strong _____ agent. A. positive; oxidizing B. negative; reducing C. negative; oxidizing D. positive; reducing E. can't be determined from information give

negative; reducing

Which reaction of glycolysis includes substrate-level phosphorylation, a very different mechanism than oxidative phosphorylation? A. Hexokinase B. Phophoglycerate C. Phosphofructokinase D. Glyceraldehyde 3-phosphate E. PEP carboxykinase

phosphoglycerate kinase

Which enzyme of gluconeogenesis requires biotin as a coenzyme? A. PEP carboxykinase B. Glucose 6-phosphatase C. Aldolase D. Pyruvate carboxylase E. Pyruvate kinase

pyruvate carboxylase

To control the flux through a pathway, it is best to regulate A. reversible reactions B. the fastest reactions C. substrate-limited reactions D. enzyme-limited reactions E. None of the above

reversible reactions

In hepatocytes, the enzyme hexokinase IV (glucokinase), which catalyzes the conversion of glucose to glucose 6-phosphate, is regulated by a regulatory protein that A. inhibits hexokinase IV when blood glucose levels are high B. irreversibly inactivates hexokinase IV C. phosphorylates hexokinase IV D. sequesters hexokinase IV inside the nucleus E. degrades hexokinase IV

sequesters hexokinase IV inside the nucleus

Glycogen phosphorylase, which is involved in the breakdown of glycogen, catalyzes A. cleavage of (α 1 → 6) glycosidic linkages. B. a hydrolysis reaction. C. the removal of glucose residues from the reducing end. D. the attack on a glycosidic bond by inorganic phosphate. E. adding a phosphate group to glycogen to activate its reducing end.

the attack on a glycosidic bond by inorganic phosphate.

All are true for the isomerase reaction of glucose-6-phosphate to fructose-6-phosphate EXCEPT: A. Mg2+ is required for activity B. it is an aldose to ketose isomerization C. "moving" the carbonyl from C1 to C2 creates a new primary alcohol group at C1 D. the reaction is irreversible with a large negative delta G E. the enzyme belongs to the isomerase class of enzymes

the reaction is irreversible with a large negative delta G