unit 4 Flashcards
1) Anaerobic glycolysis can produce ATP at a much faster rate than aerobic oxidative phosphorylation.
Answer: TRUE
2) Which of the following types of reaction does NOT occur in glycolysis? A) Isomerization B) Nucleophilic attack C) Aldol condensation D) Oxidation E) Dehydration
Answer: C
3) The standard free energy change of the glycolytic pathway to pyruvate is -79.9 kJ/mol, while the standard free energy change associated with gluconeogenesis from pyruvate is -42.7 kJ/mol. What would the standard free energy change be for a direct reversal of the glycolytic pathway.
Answer: +79.9kJ/mol
4) Glycolysis is regulated primarily by:
A) the availability of glucose-6-phosphate.
B) three strongly endergonic, nonequilibrium reactions.
C) three strongly exergonic, nonequilibrium reactions.
D) allosteric effectors of pyruvate kinase.
E) phosphorylation of phosphofructokinase.
Answer: C
5) Which of the following statements about regulation of phosphofructokinase is FALSE?
A) AMP is an activator.
B) ADP is an activator.
C) Citrate is an inhibitor.
D) Fructose 2,6-bisphosphate is an activator.
E) ATP decreases the apparent Km for fructose-6-phosphate.
Answer: E
6) Liver pyruvate kinase is activated by dephosphorylation in response to glucagon.
Answer: FALSE
7) Hexokinase, phosphofructokinase and pyruvate kinase are each subject to ________ control.
Answer: allosteric
8) Fructose-1,6-bisphosphate is a feedforward ________ activator of liver pyruvate kinase.
Answer: allosteric
9) The oxidation of glucose to lactate has a standard free energy change of approximately -196 kJ/mol. Calculate the efficiency of energy conversion if the standard free energy change for the production of ATP from ADP and inorganic phosphate is +32.2 kJ/mol.
Answer: 33.8%
10) All of the reactions of both glycolysis and gluconeogenesis occur in the cytosol.
Answer: FALSE
11) The flux rate through the gluconeogenic pathway is directly proportional to the amount of carbohydrate in the diet.
Answer: FALSE
12) Much of the regulation of gluconeogenesis is a result of the inhibition of glycolysis.
Answer: TRUE
13) Which of the following cannot be used as a precursor for gluconeogenesis? A) Glycerol B) Pyruvate C) Lactate D) Leucine E) Alanine
Answer: D
14) Flux through the pentose phosphate pathway is controlled mainly by the NADP+/NADPH ratio in the cell.
Answer: TRUE
15) The primary gluconeogenic organ in animals is: A) skeletal muscle. B) kidney medulla. C) kidney cortex. D) liver. E) heart muscle.
Answer: D
16) ________ from muscle working anaerobically is released to blood and can be taken up by liver where it is converted to pyruvate by the enzyme lactate dehydrogenase.
Answer: Lactate
17) The Pasteur effect describes the observation that yeast-metabolizing glucose anaerobically will dramatically increase their rate of glucose utilization when provided with air.
Answer: FALSE
18) Both glycolysis and gluconeogenesis are controlled by fructose 2,6-bisphosphate in response to hormones.
Answer: TRUE
19) Pyruvate carboxylase and phosphoenolpyruvate carboxykinase catalyze reactions of gluconeogenesis that bypass the reaction of glycolysis that is catalyzed by ________.
Answer: pyruvate kinase
20) Glycogen is a major energy source for skeletal muscle contraction.
Answer: TRUE
21) Polysaccharide digestion and glycogen breakdown involve sequential cleavage from ________ ends of glucose polymers.
Answer: non-reducing
22) The major product from the action of glycogen phosphorylase and the debranching enzyme glucantransferase is ________.
Answer: glucose-1-phosphate
23) Which of the following is NOT involved in glycogen synthesis? A) UDP-glucose B) Glycogenin C) Amylo-(1,4 to 1,6)-transglycosylase D) Glycogen synthase E) Glycogen phosphorylase
Answer: E
24) Which statement about control of glycogen metabolism is INCORRECT?
A) Epinephrine signals glycogen breakdown in muscle.
B) Glucagon signals glycogen breakdown in liver.
C) Glycogen phosphorylase is activated by phosphorylation.
D) Glycogen synthase is phosphorylated at only one site.
E) Glycogen synthase is activated by dephosphorylation.
Answer: D
25) Phosphorylases and phosphatases catalyze the same reaction, the removal of a phosphate group.
Answer: FALSE
26) The pentose phosphate pathway provides ________ for reductive biosynthesis and ________ for nucleic acid biosynthesis.
Answer: NADPH, ribose-5-phosphate
1) Which of the following techniques can be used to quantify protein-protein interactions? A) Co-immunoprecipitation B) Affinity chromatography C) Chemical cross-linking D) Surface plasmon resonance E) The two-hybrid system
Answer: D
2) Oxaloacetate is replenished via the ________ in plants and bacteria.
Answer: glyoxylate pathway
3) The glyoxylate cycle in plants and bacteria can be used for net carbohydrate synthesis from fat because isocitrate lyase yields glyoxylate and ________ without the loss of two carbons as occurs in the citric acid cycle.
Answer: succinate
4) All of the enzymes of the citric acid cycle are located in the mitochondrion.
Answer: TRUE
5) Which of the following does NOT apply to the reaction catalyzed by the pyruvate dehydrogenase complex?
A) The process is highly exergonic and essentially irreversible in vivo.
B) Each intermediate in the five step reaction is able to diffuse to the next active site in a sequential manner.
C) It takes place in the mitochondrion.
D) It is an oxidative decarboxylation.
E) The product is acetyl CoenzymeA.
Answer: B
6) NAD+, coenzyme A, thiamine pyrophosphate, lipoic acid and FAD are all cofactors used in the reaction catalyzed by pyruvate dehydrogenase.
Answer: TRUE
7) The citric acid cycle is classed as a reductive pathway as it produces reduced electron carriers.
Answer: FALSE
8) The two carbon atoms that are lost as CO2 in the third and fourth steps of the citric acid cycle are the same as the two carbon atoms of acetyl CoA because of the stereochemistry of the isocitrate dehydrogenase reaction.
Answer: FALSE
9) Which of the following enzymes catalyzes a reaction of the citric acid cycle that does NOT produce reduced electron carriers? A) Malate dehydrogenase B) Succinate dehydrogenase C) α-ketoglutarate dehydrogenase D) Isocitrate dehydrogenase E) Succinyl —CoA synthetase
Answer: E
10) Arsenic poisoning acts by inhibiting the citric acid cycle at the point of both pyruvate dehydrogenase and α-ketoglutarate dehydrogenase because it makes a stable adduct with the ________ groups of the dihydrolipoamide intermediate.
Answer: sulphydryl
