Question 1

If you incubate ¹⁴C-CO₂ with liver extracts capable of performing gluconeogenesis,where does the radioactive label end up?

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Question 2

Explain the biochemical basis of the human metabolic disorder called lactose intolerance.

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Question 3

An extract of adipose (fat)tissue can metabolize glucose to CO₂.When glucose labeled with ¹⁴C in either C-1 or C-6 was added to the extract,¹⁴CO₂ was released with the time courses shown below.What is the major path of glucose oxidation in this extract? Explain how you reached this conclusion.

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Question 4

Explain with words,diagrams,or structures why lactate accumulates in the blood during bursts of very vigorous exercise (such as a 100-meter dash).

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Question 5

During strenuous activity,muscle tissue demands large quantities of ATP,compared with resting muscle.In white skeletal muscle (in contrast with red muscle),ATP is produced almost exclusively by fermentation of glucose to lactate.If a person had white muscle tissue devoid of the enzyme lactate dehydrogenase,how would this affect his or her metabolism at rest and during strenuous exercise?

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Question 6

When glucose labeled with a ¹⁴C at C-1 (the aldehyde carbon)passes through glycolysis,the glyceraldehyde 3-phosphate that is produced from it still contains the radioactive carbon atom.Draw the structure of glyceraldehyde 3-phosphate,and circle the atom(s)that would be radioactive.

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Question 7

The bacterium E.coli can grow in a medium in which the only carbon source is glucose.How does this organism obtain ribose 5-phosphate for the synthesis of ATP? (Do not describe ATP synthesis,just the origin of ribose 5-phosphate. )Show structures and indicate where cofactors participate.

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Question 8

If brewer's yeast is mixed with pure sugar (glucose)in the absence of phosphate (P_i),no ethanol is produced.With the addition of a little P_i,ethanol production soon begins.Explain this observation in 25 words or less.

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Question 9

Explain why the phosphorolysis of glycogen is more efficient than the hydrolysis of glycogen in mobilizing glucose for the glycolytic pathway.

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Question 10

Draw the structure of 1,3-bisphosphoglycerate.Indicate with an arrow the phosphate ester,and circle the phosphate group for which the free energy of hydrolysis is very high.

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Question 11

Rat liver is able to metabolize glucose by both the glycolytic and the pentose phosphate pathways.Indicate in the blanks if the following are properties of glycolytic (G),pentose phosphate (P),both (G + P),or neither (0): _____ NAD⁺ is involved. _____ CO₂ is liberated. _____ Phosphate esters are intermediates. _____ Glyceraldehyde 3-phosphate is an intermediate. _____ Fructose 6-phosphate is an intermediate.

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Question 12

Describe the process of glycogen breakdown in muscle.Include a description of the structure of glycogen,the nature of the breakdown reaction and the breakdown product,and the required enzyme(s).

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Question 13

Describe the fate of pyruvate,formed by glycolysis in animal skeletal muscle,under two conditions: (a)at rest,and (b)during an all-out sprint.Show enough detail in your answer to explain why pyruvate metabolism is different in these two cases.

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Question 14

The yeast used in brewing the alcoholic beverage beer can break down glucose either aerobically or anaerobically using alcoholic fermentation.Explain why beer is brewed under anaerobic conditions.

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Question 15

What are the biological functions of the pentose phosphate pathway?

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Question 16

Two reactions in glycolysis produce ATP.For each of these,show the name and structure of reactant and product,indicate which cofactors participate and where,and name the enzymes.

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Question 17

In gluconeogenesis,how do animals convert pyruvate to phosphoenolpyruvate? Show structures,enzymes,and cofactors.

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Question 18

What is gluconeogenesis,and what useful purposes does it serve in people?

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Question 19

Yeast can metabolize D-mannose to ethanol and CO₂.In addition to the glycolytic enzymes,the only other enzyme needed is phosphomannose isomerase,which converts mannose 6-phosphate to fructose 6-phosphate.If mannose is converted to ethanol and CO₂ by the most direct pathway,which of the compounds and cofactors in this list are involved?

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Quiz 14: Glycolysis, gluconeogenesis, and the Pentose Phosphate Pathway

If you incubate 14C-CO2 with liver extracts capable of performing gluconeogenesis,where does the radioactive label end up?