Pregunta 1
Pregunta
Glycolysis is the name given to a metabolic pathway occurring in many different cell types. It consists of 11 enzymatic steps that convert glucose to lactic acid. Glycolysis is an example of:
Pregunta 2
Pregunta
The anaerobic conversion of 1 mol of glucose to 2 mol of lactate by fermentation is accompanied by a net gain of:
Respuesta
-
1 mol of ATP.
-
1 mol of NADH.
-
2 mol of ATP.
-
2 mol of NADH.
-
none of the above.
Pregunta 3
Pregunta
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:
Respuesta
-
A) dihydroxyacetone phosphate → glycerol 3-phosphate
B) glucose 6-phosphate → fructose 6-phosphate
C) isocitrate → α-ketoglutarate
D) oxaloacetate → malate
E) pyruvate → lactate
-
dihydroxyacetone phosphate → glycerol 3-phosphate
-
glucose 6-phosphate → fructose 6-phosphate
-
isocitrate → α-ketoglutarate
-
oxaloacetate → malate
-
pyruvate → lactate
Pregunta 4
Pregunta
If glucose labeled with 14C in C-1 were fed to yeast carrying out the ethanol fermentation, where would the 14C label be in the products?
Respuesta
-
In C-1 of ethanol and CO2
-
In C-1 of ethanol only
-
In C-2 (methyl group) of ethanol only
-
In C-2 of ethanol and CO2
-
In CO2 only
Pregunta 5
Pregunta
The conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of pyruvate by the glycolytic pathway results in a net formation of:
Respuesta
-
1 mol of NAD+ and 2 mol of ATP.
-
1 mol of NADH and 1 mol of ATP.
-
2 mol of NAD+ and 4 mol of ATP.
-
2 mol of NADH and 2 mol of ATP.
-
2 mol of NADH and 4 mol of ATP.
Pregunta 6
Pregunta
In an anaerobic muscle preparation, lactate formed from glucose labeled in C-3 and C-4 would be labeled in:
Respuesta
-
all three carbon atoms.
-
only the carbon atom carrying the OH.
-
only the carboxyl carbon atom.
-
only the methyl carbon atom.
-
the methyl and carboxyl carbon atoms.
Pregunta 7
Pregunta
Which of the following statements is not true concerning glycolysis in anaerobic muscle?
Respuesta
-
Fructose 1,6-bisphosphatase is one of the enzymes of the pathway.
-
It is an endergonic process.
-
It results in net synthesis of ATP.
-
It results in synthesis of NADH.
-
Its rate is slowed by a high [ATP]/[ADP] ratio.
Pregunta 8
Pregunta
When a muscle is stimulated to contract aerobically, less lactic acid is formed than when it contracts anaerobically because:
Respuesta
-
glycolysis does not occur to significant extent under aerobic conditions.
-
muscle is metabolically less active under aerobic than anaerobic conditions.
-
the lactic acid generated is rapidly incorporated into lipids under aerobic conditions.
-
under aerobic conditions in muscle, the major energy-yielding pathway is the pentose phosphate pathway, which does not produce 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.
Pregunta 9
Pregunta
Glycolysis in the erythrocyte produces pyruvate that is further metabolized to:
Respuesta
-
CO2.
-
ethanol.
-
glucose.
-
hemoglobin.
-
lactate.
Pregunta 10
Pregunta
When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase, the final mixture contains twice as much glucose 6-phosphate as fructose 6-phosphate. Which one of the following statements is most nearly correct, when applied to the reaction below (R = 8.315 J/mol·K and T = 298 K)?
Glucose 6-phosphate ↔ fructose 6-phosphate
Pregunta 11
Pregunta
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?
Respuesta
-
If the concentrations of the two products are high relative to that of fructose 1,6-bisphosphate.
-
The reaction will not go to the right spontaneously under any conditions because the ΔG'° is positive.
-
Under standard conditions, enough energy is released to drive the reaction to the right.
-
When there is a high concentration of fructose 1,6-bisphosphate relative to the concentration of products.
-
When there is a high concentration of products relative to the concentration of fructose 1,6-bisphosphate.
Pregunta 12
Pregunta
Glucose labeled with 14C in C-1 and C-6 gives rise in glycolysis to pyruvate labeled in:
Respuesta
-
A and C.
-
all three carbons.
-
its carbonyl carbon.
-
its carboxyl carbon.
-
its methyl carbon.
Pregunta 13
Pregunta
If glucose labeled with 14C at C-1 (the aldehyde carbon) were metabolized in the liver, the first radioactive pyruvate formed would be labeled in:
Respuesta
-
all three carbons.
-
both A and C.
-
its carbonyl carbon.
-
its carboxyl carbon.
-
its methyl carbon.
Pregunta 14
Pregunta
In an anaerobic muscle preparation, lactate formed from glucose labeled in C-2 would be labeled in:
Respuesta
-
all three carbon atoms.
-
only the carbon atom carrying the OH.
-
only the carboxyl carbon atom.
-
only the methyl carbon atom.
-
the methyl and carboxyl carbon atoms.
Pregunta 15
Pregunta
If glucose labeled with 14C in C-3 is metabolized to lactate via fermentation, the lactate will contain 14C in:
Respuesta
-
all three carbon atoms.
-
only the carbon atom carrying the OH.
-
only the carboxyl carbon atom.
-
only the methyl carbon atom.
-
the methyl and carboxyl carbon atoms.
Pregunta 16
Pregunta
Which of these cofactors participates directly in most of the oxidation-reduction reactions in the fermentation of glucose to lactate?
Pregunta 17
Pregunta
In comparison with the resting state, actively contracting human muscle tissue has a:
Respuesta
-
higher concentration of ATP.
-
higher rate of lactate formation.
-
lower consumption of glucose.
-
lower rate of consumption of oxygen
-
lower ratio of NADH to NAD+.
Pregunta 18
Pregunta
The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except:
Respuesta
-
ATP synthesis.
-
catalysis by phosphoglycerate kinase.
-
oxidation of NADH to NAD+.
-
the formation of 1,3-bisphosphoglycerate.
-
utilization of Pi.
Pregunta 19
Pregunta
The first reaction in glycolysis that results in the formation of an energy-rich compound (i.e., a compound whose hydrolysis has a highly negative ΔG'°) is catalyzed by:
Pregunta 20
Pregunta
Which of the following is a cofactor in the reaction catalyzed by glyceraldehyde 3-phosphate dehydrogenase?
Pregunta 21
Pregunta
In the phosphoglycerate mutase reaction, the side chain of which amino acid in the enzyme is transiently phosphorylated as part of the reaction?
Respuesta
-
serine
-
threonine
-
tyrosine
-
histidine
-
arginine
Pregunta 22
Pregunta
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?
Respuesta
-
2-phosphoglycerate
-
Glucose
-
Glyoxylate
-
Phosphoenolpyruvate
-
Pyruvate
Pregunta 23
Pregunta
Glycogen is converted to monosaccharide units by:
Respuesta
-
glucokinase.
-
glucose-6-phosphatase
-
glycogen phosphorylase.
-
glycogen synthase.
-
glycogenase.