Question 1

What is the function of the enzyme invertase?

Accepted Answer

A) It cleaves lactose into galactose and glucose. 
B) It converts glucose into fructose. 
C) It interconverts glucose between its R and S enantiomers. 
D) It cleaves sucrose into glucose and fructose. 
A) It cleaves lactose into galactose and glucose. 
B) It converts glucose into fructose. 
C) It interconverts glucose between its R and S enantiomers. 
D) It cleaves sucrose into glucose and fructose. D

Question 2

Which amino acid's residue plays a role in the phosphoglycerate mutase reaction in glycolysis for muscle and yeast?

Accepted Answer

A) Leucine. 
B) Lysine. 
C) Alanine. 
D) Histidine. 
A) Leucine. 
B) Lysine. 
C) Alanine. 
D) Histidine. D

Question 3

Yeast will normally convert pyruvate to ethanol.Why is this better for the yeast than a conversion to lactate?

Accepted Answer

A) Conversion to ethanol releases more NAD+ per mole than the conversion to lactate. 
B) The carbon atoms are more oxidized in ethanol than in lactate. 
C) Ethanol is neutral,but lactate production is accompanied by a sharp decrease in pH. 
D) Ethanol production is not better.Yeast normally produces ethanol and lactate in equimolar amounts. 
A) Conversion to ethanol releases more NAD+ per mole than the conversion to lactate. 
B) The carbon atoms are more oxidized in ethanol than in lactate. 
C) Ethanol is neutral,but lactate production is accompanied by a sharp decrease in pH. 
D) Ethanol production is not better.Yeast normally produces ethanol and lactate in equimolar amounts. C

Question 4

There are four enzymes that can catalyze the first step of glycolysis.They are hexokinases I,II and III and glucokinase (hexokinase IV).Hexokinases I,II and III have Km values near 0.1 mM.Glucokinase has a Km range of 2-5 mM.If after a heavy meal the blood glucose level rises to 8 mM which statement will be true?

Accepted Answer

A) At this high blood glucose level all four hexokinases are saturated with substrate. 
B) Hexokinases I,II and III are catalyzing at their maximum rate,but glucokinase can still respond to increases in blood glucose levels. 
C) None of the enzymes is saturated.All of them help to increase the rate of glycolysis. 
D) The flux through glucokinase will be extremely low.The only significant catalysis is done by hexokinases I,II and III. 
A) At this high blood glucose level all four hexokinases are saturated with substrate. 
B) Hexokinases I,II and III are catalyzing at their maximum rate,but glucokinase can still respond to increases in blood glucose levels. 
C) None of the enzymes is saturated.All of them help to increase the rate of glycolysis. 
D) The flux through glucokinase will be extremely low.The only significant catalysis is done by hexokinases I,II and III.

Question 5

The conversion of pyruvate to ethanol also causes the ________.

Accepted Answer

A) oxidation of NADH 
B) production of ADP 
C) consumption of O² 
D) generation of an ion gradient across mitochondrial membranes 
A) oxidation of NADH 
B) production of ADP 
C) consumption of O² 
D) generation of an ion gradient across mitochondrial membranes

Question 6

In the liver,________ has a main use for maintaining blood glucose,but it can also be used to synthesize glycogen,or enter the pentose phosphate pathway to produce ribose 5-phosphate.

Accepted Answer

A) glucose-1-phosphate 
B) glucose-1,6-bisphosphate 
C) fructose-6-phosphate 
D) glucose-6-phosphate 
A) glucose-1-phosphate 
B) glucose-1,6-bisphosphate 
C) fructose-6-phosphate 
D) glucose-6-phosphate

Question 7

Glucagon is a pancreatic hormone that is produced in response to low blood sugar levels.At high glucagon concentrations glycolysis is slowed.

Accepted Answer

A) True 
 B)False

Question 8

Some reaction steps in the glycolytic pathway have positive standard free energy changes.Which statements apply?

Accepted Answer

A) The standard free energy for these steps is not the same as the actual free energy change in cells.The actual free energy change must be negative or zero. 
B) The reaction steps with positive standard free energy changes are likely to be regulatory steps for the pathway. 
C) The steps with a positive standard free energy change are the fastest steps in the pathway. 
D) The steps with a positive standard free energy change must be coupled to an ATP →ADP conversion. 
A) The standard free energy for these steps is not the same as the actual free energy change in cells.The actual free energy change must be negative or zero. 
B) The reaction steps with positive standard free energy changes are likely to be regulatory steps for the pathway. 
C) The steps with a positive standard free energy change are the fastest steps in the pathway. 
D) The steps with a positive standard free energy change must be coupled to an ATP →ADP conversion.

Question 9

ATP is a cosubstrate of the enzyme PFK-1.In most species ATP is also an inhibitor of PFK-1 at higher concentrations.This seems to violate Le Chatelier's Principle.Which statement below would provide a suitable explanation?

Accepted Answer

A) PFK-1 must be phosphorylated by ATP in the active site and the phosphorylated PFK-1 must be the less active form. 
B) There must be another cofactor interacting with ATP at high concentrations to achieve inhibition of PFK-1. 
C) ATP actually activates the reverse of the reaction preceding the PFK-1 step in the pathway.It likely has no direct effect on PFK-1. 
D) There are two sites on PFK-1 that bind ATP.One is the active site;the other is the regulatory site where inhibition occurs. 
A) PFK-1 must be phosphorylated by ATP in the active site and the phosphorylated PFK-1 must be the less active form. 
B) There must be another cofactor interacting with ATP at high concentrations to achieve inhibition of PFK-1. 
C) ATP actually activates the reverse of the reaction preceding the PFK-1 step in the pathway.It likely has no direct effect on PFK-1. 
D) There are two sites on PFK-1 that bind ATP.One is the active site;the other is the regulatory site where inhibition occurs.

Question 10

Cells that form ATP mainly by glycolysis are

Accepted Answer

A) anaerobic yeasts. 
B) lactic acid bacteria. 
C) kidney medulla cells. 
D) A and B. 
E) A,B and C. 
A) anaerobic yeasts. 
B) lactic acid bacteria. 
C) kidney medulla cells. 
D) A and B. 
E) A,B and C.

Question 11

Glycolysis occurs in the cytosol of eukaryotes.

Accepted Answer

A) True 
 B)False

Question 12

What are the effects of protein kinase A on PFK-2 and pyruvate kinase?

Accepted Answer

A) Phosphorylates PFK-2;dephosphorylated pyruvate kinase;both enzymes are inhibited. 
B) Phosphorylates both enzymes;inhibits both enzymes. 
C) Dephosphorylates both enzymes;inhibits both enzymes. 
D) Dephosphorylates PFK-2;phosphorylates pyruvate kinase;activates PFK-2;inhibits pyruvate kinase. 
A) Phosphorylates PFK-2;dephosphorylated pyruvate kinase;both enzymes are inhibited. 
B) Phosphorylates both enzymes;inhibits both enzymes. 
C) Dephosphorylates both enzymes;inhibits both enzymes. 
D) Dephosphorylates PFK-2;phosphorylates pyruvate kinase;activates PFK-2;inhibits pyruvate kinase.

Question 13

Glucose is the only hexose which can enter the glycolytic pathway.

Accepted Answer

A) True 
 B)False

Question 14

A patient is found to be deficient in the enzyme galactose 1-phosphate uridylyltransferase.Specifically due to this deficiency what might a doctor recommend?

Accepted Answer

A) Avoid all strenuous exercise. 
B) Eat a fat-free diet. 
C) Increase intake of vitamin C. 
D) Avoid ingestion of milk and milk products. 
A) Avoid all strenuous exercise. 
B) Eat a fat-free diet. 
C) Increase intake of vitamin C. 
D) Avoid ingestion of milk and milk products.

Question 15

Glucose is the only monosaccharide that can enter the glycolytic pathway at the first step.All other monosaccharides enter at a subsequent step in the pathway.

Accepted Answer

A) True 
 B)False

Question 16

In the presence of arsenate poisoning

Accepted Answer

A) ATP production proceeds via a reaction that involves 1,3-bisphosphoglycerate. 
B) glycolysis is interrupted. 
C) a net production of 2 molecules of ATP occurs. 
D) All of the above. 
E) None of the above. 
A) ATP production proceeds via a reaction that involves 1,3-bisphosphoglycerate. 
B) glycolysis is interrupted. 
C) a net production of 2 molecules of ATP occurs. 
D) All of the above. 
E) None of the above.

Question 17

Fermentation is a process where electrons from glycolysis - in the form of NADH - are passed to

Accepted Answer

A) the membrane associated electron transport chain. 
B) only ethanol. 
C) ethanol and other organic compounds. 
D) oxygen. 
A) the membrane associated electron transport chain. 
B) only ethanol. 
C) ethanol and other organic compounds. 
D) oxygen.

Question 18

Which of the following enzymatic reactions are control points for glycolysis?

Accepted Answer

A) Glucose 6-phosphate isomerase. 
B) Aldolase. 
C) Both A and B. 
D) Neither A nor B. 
A) Glucose 6-phosphate isomerase. 
B) Aldolase. 
C) Both A and B. 
D) Neither A nor B.

Question 19

More than one step in the glycolytic pathway is subject to regulation.It might seem most efficient to regulate only the first step of a pathway to avoid buildup of intermediates and to conserve materials and energy.Why is the first step of glycolysis not the only regulated step?

Accepted Answer

A) Some sugars can enter the glycolytic pathway beyond the first step.If steps other than step one were not regulated,the breakdown of these sugars would be essentially uncontrolled. 
B) Having more than one regulated step in the pathway allows for feedback inhibition. 
C) Control of a single step in a reaction pathway is difficult because the concentrations of enzymes in cells are very low.It's easier to control more than one enzyme. 
D) All the ATP in a cell would be depleted very quickly if only the first step of glycolysis were regulated. 
A) Some sugars can enter the glycolytic pathway beyond the first step.If steps other than step one were not regulated,the breakdown of these sugars would be essentially uncontrolled. 
B) Having more than one regulated step in the pathway allows for feedback inhibition. 
C) Control of a single step in a reaction pathway is difficult because the concentrations of enzymes in cells are very low.It's easier to control more than one enzyme. 
D) All the ATP in a cell would be depleted very quickly if only the first step of glycolysis were regulated.

Question 20

How many ATP molecules are consumed in the hexose stage of glycolysis for every one molecule of glucose?

Accepted Answer

A) 0;ATP is produced,not consumed,by glycolysis. 
B) 1 
C) 2 
D) 3 
E) 4 
A) 0;ATP is produced,not consumed,by glycolysis. 
B) 1 
C) 2 
D) 3 
E) 4

Exam 11: Glycolysis

What is the function of the enzyme invertase?

Which amino acid's residue plays a role in the phosphoglycerate mutase reaction in glycolysis for muscle and yeast?

Yeast will normally convert pyruvate to ethanol.Why is this better for the yeast than a conversion to lactate?

The conversion of pyruvate to ethanol also causes the ________.

In the liver,________ has a main use for maintaining blood glucose,but it can also be used to synthesize glycogen,or enter the pentose phosphate pathway to produce ribose 5-phosphate.

Glucagon is a pancreatic hormone that is produced in response to low blood sugar levels.At high glucagon concentrations glycolysis is slowed.

Some reaction steps in the glycolytic pathway have positive standard free energy changes.Which statements apply?

ATP is a cosubstrate of the enzyme PFK-1.In most species ATP is also an inhibitor of PFK-1 at higher concentrations.This seems to violate Le Chatelier's Principle.Which statement below would provide a suitable explanation?

Cells that form ATP mainly by glycolysis are

Glycolysis occurs in the cytosol of eukaryotes.

What are the effects of protein kinase A on PFK-2 and pyruvate kinase?

Glucose is the only hexose which can enter the glycolytic pathway.

A patient is found to be deficient in the enzyme galactose 1-phosphate uridylyltransferase.Specifically due to this deficiency what might a doctor recommend?

Glucose is the only monosaccharide that can enter the glycolytic pathway at the first step.All other monosaccharides enter at a subsequent step in the pathway.

In the presence of arsenate poisoning

Fermentation is a process where electrons from glycolysis - in the form of NADH - are passed to

Which of the following enzymatic reactions are control points for glycolysis?

More than one step in the glycolytic pathway is subject to regulation.It might seem most efficient to regulate only the first step of a pathway to avoid buildup of intermediates and to conserve materials and energy.Why is the first step of glycolysis not the only regulated step?

How many ATP molecules are consumed in the hexose stage of glycolysis for every one molecule of glucose?

Introduction to Biochemistry

Water

Amino Acids and the Primary Structures of Proteins

Proteins: Three-Dimensional Structure and Function

Properties of Enzymes

Mechanisms of Enzymes

Coenzymes and Vitamins

Carbohydrates

Lipids and Membranes

Introduction to Metabolism

Gluconeogenesis, the Pentose Phosphate Pathway, and Glycogen Metabolism

The Citric Acid Cycle

Electron Transport and Atp Synthesis

Photosynthesis

Lipid Metabolism

Amino Acid Metabolism

Nucleotide Metabolism

Nucleic Acids

DNA Replication, repair, and Recombination

Transcription and RNA Processing

Protein Synthesis

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