The conversion of 1 mol of pyruvate to 3 mol of CO2 via pyruvate dehydrogenase and the citric acid cycle also yields _____ mol of NADH, _____ mol of FADH2, and _____ mol of ATP (or GTP).
A) 2; 2; 2
B) 3; 1; 1
C) 3; 2; 0
D) 4; 1; 1
E) 4; 2; 1
D) 4; 1; 1
Which of the following statements about the oxidative decarboxylation of pyruvate in aerobic conditions in animal cells is correct?
A) One of the products of the reactions of the pyruvate dehydrogenase complex is a thioester of acetate.
B) The methyl (—CH3) group is eliminated as CO2.
C) The process occurs in the cytosolic compartment of the cell.
D) The pyruvate dehydrogenase complex uses all of the following as cofactors: NAD+, lipoic acid, pyridoxal phosphate (PLP), and FAD.
E) The reaction is so important to energy production that pyruvate dehydrogenase operates at full speed under all conditions.
A) One of the products of the reactions of the pyruvate dehydrogenase complex is a thioester of acetate.
Citrate synthase and the NAD+-specific isocitrate dehydrogenase are two key regulatory enzymes of the citric acid cycle. These enzymes are inhibited by:
A) acetyl-CoA and fructose 6-phosphate.
B) AMP and/or NAD+.
C) AMP and/or NADH.
D) ATP and/or NAD+.
E) ATP and/or NADH.
E) ATP and/or NADH.
Acetyl-CoA is not an intermediate of the citric acid cycle.
T
F
True
There are few, if any, humans with defects in the enzymes of the citric acid cycle.
T
F
True
Entry of acetyl-CoA into the citric acid cycle is decreased when:
A) [AMP] is high.
B) NADH is rapidly oxidized through the respiratory chain.
C) the ratio of [ATP]/[ADP] is low
D) the ratio of [ATP]/[ADP] is high.
E) the ratio of [NAD+]/[NADH] is high
D) the ratio of [ATP]/[ADP] is high.
Anaplerotic reactions .
A) produce oxaloacetate and malate to maintain constant levels of citric acid cycle intermediates.
B) produce biotin needed by pyruvate carboxylase.
C) recycle pantothenate used to make CoA.
D) produce pyruvate and citrate to maintain constant levels of citric acid cycle intermediates.
E) All choices are correct
A) produce oxaloacetate and malate to maintain constant levels of citric acid cycle intermediates.
Which of the following is not true of the citric acid cycle?
A) All enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase, which is bound to the inner mitochondrial membrane.
B) In the presence of malonate, one would expect succinate to accumulate.
C) Oxaloacetate is used as a substrate in the cycle.
D) Succinate dehydrogenase channels electrons directly into the electron transfer chain.
E) The condensing enzyme is subject to allosteric regulation by ATP and NADH.
A) All enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase, which is bound to the inner mitochondrial membrane.
Fluorocitrate is a deadly poison because it is a potent inhibitor of the enzyme citrate synthase. (Remember the POGIL question last Friday ......)
T
F
False
Which of the below is not required for the oxidative decarboxylation of pyruvate to form acetyl-CoA?
A) ATP
B) CoA-SH
C) FAD
D) Lipoic Acid
E) NAD+
A) ATP
During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase reaction in skeletal muscle must be reoxidized to NAD+ if glycolysis is to continue. The most important reaction involved in the reoxidation of NADH is:
A) dihydroxyacetone phosphate → glycerol 3-phosphate
B) glucose 6-phosphate → fructose 6-phosphate
C) isocitrate → α-ketoglutarate
D) oxaloacetate → malate
E) pyruvate → lactate
E) pyruvate → lactate
All of the following contribute to the large, negative, free-energy change upon hydrolysis of “high-energy” compounds 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.
B) low activation energy of forward reaction
Glycolysis is the name given to a metabolic pathway occurring in many different cell types. It can consist of 11 enzymatic steps that convert glucose to lactic acid. In this example glycolysis is an example of:
A) aerobic metabolism
B) anaerobic metabolism
C) a net reductive process
D) fermentation
E) oxidative phosphorylation
D) fermentation
Which one of the following statements about gluconeogenesis is false?
A) For starting materials, it can use carbon skeletons derived from certain amino acids.
B) It consists entirely of the reactions of glycolysis, operating in the reverse direction.
C) It employs the enzyme glucose 6-phosphatase.
D) It is one of the ways that mammals can maintain normal blood glucose levels between meals.
E) It requires metabolic energy (ATP or GTP).
B) It consists entirely of the reactions of glycolysis, operating in the reverse direction.
Inorganic fluoride inhibits enolase. In an anaerobic system that is metabolizing glucose as a substrate, which of the following compounds would you expect to increase in concentration following the addition of fluoride?
A) 2-phosphoglycerate
B) Glucose
C) Phosphoenolpyruvate
D) Pyruvate
E) Lactate
A) 2-phosphoglycerate
If the ΔG'° of the reaction A → B is –40 kJ/mol, under standard conditions the reaction:
A) is at equilibrium.
B) will never reach equilibrium.
C) will not occur spontaneously.
D) will proceed at a rapid rate.
E) will proceed spontaneously from left to right.
E) will proceed spontaneously from left to right.
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.
D) When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products.
During glycolysis, glucose 1-phosphate is converted to fructose 6-phosphate in two successive reactions:(1) Glucose 1-phosphate → glucose 6-phosphate ΔG'° = –7.1 kJ/mol (2) Glucose 6-phosphate → fructose 6-phosphate ΔG'° = +1.7 kJ/mol. ΔG'° for the overall reaction is:
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
C) –5.4 kJ/mol
In humans, gluconeogenesis:
A) can result in the conversion of protein into blood glucose.
B) helps to reduce blood glucose after a carbohydrate-rich meal.
C) is activated by the hormone insulin
D) is essential in the conversion of fatty acids to glucose.
E) requires the enzyme hexokinase.
A) can result in the conversion of protein into blood glucose.
The main function of the pentose phosphate pathway is to:
A) give the cell an alternative pathway should glycolysis fail.
B) provide a mechanism for the utilization of the carbon skeletons of excess amino acids.
C) supply energy.
D) supply NADH
E) supply pentoses and NADPH.
E) supply pentoses and NADPH.