Biochemistry : Reactants and Products of Glycolysis

Study concepts, example questions & explanations for Biochemistry

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Example Questions

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Example Question #1 : Reactants And Products Of Glycolysis

In which of these steps of glycolysis is ATP not produced nor is it hydrolyzed?

Possible Answers:

All of these reactions require ATP be used up or synthesized

Fructose-6-phosphate  fructose-1,6-bisphosphate

Phosphoenolpyruvate  pyruvate

Glyceraldehyde-3-phosphate  1,3-bisphosphoglycerate

Glucose  glucose-6-phosphate

Correct answer:

Glyceraldehyde-3-phosphate  1,3-bisphosphoglycerate

Explanation:

The reaction turning glyceraldehyde-3-phosphate into 1,3-bisphosphoglycerate is shown below

This step of glycolysis does not hydrolyze or generate ATP, even though a phosphate group was added onto the glyceraldehyde-3-phosphate. The energy released when  is reduced to , sometimes referred to as the energy of oxidation (of glyceraldehyde-3-phosphate).

Example Question #2 : Reactants And Products Of Glycolysis

Glycolysis involves producing energy from carbohydrates. Often times, our foods don't have just glucose, but other sugars such as fructose (in table sugar) and galactose (in milk). Let's consider fructose.

 Fructofuranose

Assuming fructose can be phosphorylated by hexokinase, in which step of glycolysis would fructose enter?

Possible Answers:

Fructose-1,6-bisphosphate

Fructose-6-phosphate

Glucose

glucose-6-phosphate

None of these

Correct answer:

Fructose-6-phosphate

Explanation:

Fructose can be directly transformed into fructose-6-phosphate by hexokinase.

Phosphofructokinase

Example Question #116 : Catabolic Pathways And Metabolism

Glucose is converted to __________ in glycolysis.

Possible Answers:

pyruvate

ADP

Correct answer:

pyruvate

Explanation:

Glycolysis, as the name suggests, is the process of lysing glucose into pyruvate. Since glucose is a six-carbon molecule and pyruvate is a three-carbon molecule, two molecules of pyruvate are produced for each molecule of glucose that enters glycolysis. Glycolysis occurs in the cytoplasm of the cell, and does not require oxygen. The net energy production is two ATP per glucose.

Example Question #4 : Reactants And Products Of Glycolysis

The second step of glycolysis involves the conversion of __________ into __________.

Possible Answers:

glucose-6-phosphate . . . fructose-6-phosphate

glucose-6-phosphate . . . dihydroxyacetone

dihydroxyacetone . . . glyceraldehyde-3-phosphate

fructose-6-phosphate . . . glucose-6-phosphate

Correct answer:

glucose-6-phosphate . . . fructose-6-phosphate

Explanation:

After glucose is converted into glucose-6-phosphate by hexokinase, glucose-6-phosphate is converted into fructose-6-phosphate. This reaction is catalyzed by phosphoglucose isomerase.

Example Question #5 : Reactants And Products Of Glycolysis

The sixth step of glycolysis results in the conversion of __________ to __________.

Possible Answers:

glyceraldehyde-3-phosphate . . . 1,3-bisphosphoglycerate

1,3-bisphosphoglycerate . . . glyceraldehyde-3-phosphate

phosphoenolpyruvate . . . pyruvate

pyruvate . . . phosphoenolpyruvate

Correct answer:

glyceraldehyde-3-phosphate . . . 1,3-bisphosphoglycerate

Explanation:

The sixth step of glycolysis involves the enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). GAPDH moves a hydrogen onto the electron acceptor  An NADH is created for each molecule of G3P formed. A phosphate group from inorganic phosphate instead of ATP replaces the hydrogen group that was taken from G3P. This creates the molecule 1,3-bisphosphoglycerate. Remember that glucose is a six-carbon sugar, and that both G3P and 1,3-bisphosphoglycerate are three-carbon sugars. Thus there are two of each of these three-carbon sugars yielded for each glucose that enters glycolysis.

Example Question #117 : Catabolic Pathways And Metabolism

The seventh reaction of glycolysis involves the conversion of __________ to __________.

Possible Answers:

phosphoenolpyruvate . . . pyruvate

3-phosphoglycerate . . . 1,3-bisphosphoglycerate

1,3-bisphosphoglycerate . . . 3-phosphoglycerate

glucose-6-phosphate . . . fructose-6-phosphate

Correct answer:

1,3-bisphosphoglycerate . . . 3-phosphoglycerate

Explanation:

The seventh reaction of glycolysis is the conversion of 1,3-bisphosphoglycerate into 3-phosphoglycerate. The phosphate group is transferred from 1,3-bisphosphoglycerate onto ADP, yielding ATP. The conversion is catalyzed by the enzyme phosphoglycerate kinase.

Example Question #3 : Reactants And Products Of Glycolysis

The net reaction for glycolysis is __________.

Possible Answers:

None of these

Correct answer:

Explanation:

One molecule of glucose produces two molecules of pyruvate. During this reaction, two ATP are used (steps 1 and 3) and four ATP are generated (two in step 6 and two in step 9), yielding a net production of 2 ATP per glucose. Also, one NADH is produced per glyceraldehyde-3-phosphate to yield a total of 2 NADH per glucose. 

Example Question #4 : Reactants And Products Of Glycolysis

How many pyruvates are created from the complete glycolysis of one molecule of glucose?

Possible Answers:

Correct answer:

Explanation:

Glucose is a six-carbon molecule, and pyruvate is a three carbon molecule. From the name, we know that glycolysis involves the lysis, or splitting of glucose. As such, the products of glycolysis include two molecules of pyruvate.

Example Question #5 : Reactants And Products Of Glycolysis

Which of the following is true about the glycolysis pathway?

Possible Answers:

One NADH molecule is formed per molecule of glucose.

Each pyruvate contains two carbon atoms.

Each glucose molecule is converted into three molecules of pyruvate.

 gas is required for glycolysis to occur.

There is a net gain of two ATP molecules for each glucose broken down.

Correct answer:

There is a net gain of two ATP molecules for each glucose broken down.

Explanation:

Each glucose molecule is converted into two pyruvate molecules, with three carbon atoms each. During glycolysis, two NADH molecules are formed per glucose. Oxygen is not necessary -- one major feature of glycolysis is that it produces energy anaerobically. It yields ATP, with a net gain of two ATP molecules for each glucose consumed.

Example Question #3 : Reactants And Products Of Glycolysis

What is the net yield of ATP from glycolysis?

Possible Answers:

Correct answer:

Explanation:

Two separate steps of glycolysis each create 2 ATP (4 ATP total). However, the first and third steps involved in this process require an input of energy in order to work. Thus, the net yield of ATP from glycolysis is actually only 2 ATP. These ATP are produced via substrate-level phosphorylation.

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