BIO C HE MIA I I – ĆW ICZ E NI A
L I S T A 1
do wykładu dr. hab. inż . P. Dobryszyckiego
G l i k o l i z a i g l u k o n e o g e n e z a
1. Which of the following answers complete the sentence correctly? Hexokinase a) catalyzes the conversion of glucose 6-phosphate into fructose 1,6-bisphosphate.
b) requires Ca2+ for activity.
c) uses inorganic phosphate to form glucose 6-phosphate.
d) catalyzes the transfer of a phosphoryl group to a variety of hexoses.
e) catalyzes a phosphoryl shift reaction.
2. Which of the following answers complete the sentence correctly? The phosphofructokinase and the pyruvate kinase reactions are similar in that
a) both generate ATP.
b) both involve a "high-energy" sugar derivative.
c) both involve three-carbon compounds.
d) both are essentially irreversible.
e) both enzymes undergo induced-fit rearrangements after binding of the substrate.
3. If the C-l carbon of glucose were labeled with 14C, which of the carbon atoms in pyruvate would be labeled after glycolysis?
a) the carboxylate carbon
b) the carbonyl carbon
c) the methyl carbon
4. Starting with fructose 6-phosphate and proceeding to pyruvate, what is the net yield of ATP
molecules?
a) 1
b) 2
c) 3
d) 4
e) 5
5. Since lactate is a "dead-end" product of metabolism in the sense that its sole fate is to be reconverted into pyruvate, what is the purpose of its formation?
6. When blood glucose levels are low, glucagon is secreted. Which of the following are the effects of increased glucagon levels on glycolysis and related reactions in liver?
a) Phosphorylation of phosphofructokinase 2 and fructose bisphosphatase 2 occurs.
b) Dephosphorylation of phosphofructokinase 2 and fructose bisphosphatase 2 occurs.
c) Phosphofructokinase is activated.
d) Phosphofructokinase is inhibited.
e) Glycolysis is accelerated.
f) Glycolysis is slowed down.
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7. Match hexokinase and glucokinase with the descriptions from the right column that are appropriate.
a) Hexokinase
(1) is found in the liver
b) Glucokinase
(2) is found in nonhepatic tissues
(3) is specific for glucose
(4) has a broad specificity for hexoses
(5) requires ATP for reaction
(6) has a high KM for glucose.
(7) is inhibited by glucose 6-phosphate.
8. Which of the following statements about glucose transporters is NOT true?
a) They are transmembrane proteins.
b) They accomplish the movement of glucose across animal cell plasma membranes.
c) Their tissue distribution and concentration can depend on the tissue type and metabolic state of the organism.
d) Their glucose binding site is moved from one side of the membrane to the other by rotation of the entire protein.
e) They constitute a family of five isoforms of a protein.
9. Which of the following statements about gluconeogenesis are true?
a) It occurs actively in the muscle during periods of exercise.
b) It occurs actively in the liver during periods of exercise or fasting.
c) It occurs actively in adipose tissue during feeding.
d) It occurs actively in the kidney during periods of fasting.
e) It occurs actively in the brain during periods of fasting.
10. The following is the sequence of reactions of gluconeogenesis from pyruvate to phosphoenolpyruvate:
Pyruvate → oxaloacetate → malate → oxaloacetate → phosphoenolpyruvate A B C D
Match the capital letters indicating the reactions of the gluconeogenic pathway with the following statements:
a) occurs in the mitochondria
e)
requires ATP
b) occurs in the cytosol
f)
requires GTP
c) produces CO2
g)
is regulated by acetyl CoA
d) consumes CO2
h)
requires a biotin cofactor
11. Which of the following statements correctly describe what happens when acetyl CoA is abundant?
a) Pyruvate carboxylase is activated.
b) Phosphoenolpyruvate carboxykinase is activated.
c) Phosphofructokinase is activated.
d) If ATP levels are high, oxaloacetate is diverted to gluconeogenesis.
e) If ATP levels are low, oxaloacetate is diverted to gluconeogenesis.
12. In the coordinated control of phosphofructokinase (PFK) and fructose 1,6-bisphosphatase (F-1,6-BPase),
a) citrate inhibits PFK and stimulates F-1,6-BPase.
b) fructose 2,6-bisphosphate inhibits PFK and stimulates F-1,6-BPase.
c) acetyl-CoA inhibits PFK and stimulates F-l,6-BPase.
d) AMP inhibits PFK and stimulates F-l,6-BPase.
e) NADPH inhibits PFK and stimulates F-1,6-BPase.
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13. Indicate which of the conditions listed in the right column increase the activity of the glycolysis or gluconeogenesis pathways.
a) glycolysis
(1) increase in ATP
b) gluconeogenesis
(2) increase in AMP
(3) increase in F-2,6-BP
(4) increase in citrate
(5) increase in acetyl-CoA
(6) increase in insulin
(7) increase in glucagon
(8) starvation
(9) fed state
14. In liver, Vmax for fructose bisphosphatase is three to four times higher than Vmax for phosphofructokinase, whereas in muscle it is only about 10 percent of that of phosphofructokinase.
Explain this difference.
15. In muscle, lactate dehydrogenase produces lactate from pyruvate, whereas in the heart it preferentially synthesizes pyruvate from lactate. Explain how this is possible.
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