BCCB2000 Lecture 16 Questions

Question 1

Substrate level phosphorylation: A. describes the conversion of ADP into ATP with the addition of inorganic phosphate every place throughout the cell. B. describes the formation of ADP by phosphoryl group transfer from 1,3 bisphosphoglycerate. C. is the formation of ATP by phosphoryl group transfer from a higher energy compound. D. Both A and C

Answer 1

C. is the formation of ATP by phosphoryl group transfer from a higher energy compound.

Question 2

Arsenate: A. competes with NAD+ for the binding site in 1,3-bisphosphoglycerate. B. competes with phosphate for its binding site in glyceraldehyde 3-phosphate dehydrogenase. C. produces a stable analog of 1,3-bisphosphoglycerate. D. All of the above

Answer 2

B. competes with phosphate for its binding site in glyceraldehyde 3-phosphate dehydrogenase.

Question 3

Glucose is the major fuel of most organisms it’s benefits include: A. supplying carbon for other metabolites B. small molecule with no polar functional groups C. a free energy of oxidation = -2864 kJ/mol D. an enthalpy = -2864 kJ/mol

Answer 3

A. supplying carbon for other metabolites C. a free energy of oxidation = -2864 kJ/mol

Question 4

Transfer of the phosphoryl group from PEP to ADP is an example of: A. a mutase reaction B. isomerization. C. dehydrogenase D. substrate-level phosphorylation

Answer 4

D. substrate-level phosphorylation

Question 5

Which one of the following statements concerning glycolysis is correct? A. The conversion of glucose to lactate requires the presence of oxygen B. Hexokinase is important in hepatic glucose metabolism only in the absorptive period following consumption of a carbohydrate meal C. Fructose 2,6 bisphosphate is a potent inhibitor of phosphofructokinase D. The regulated reactions are also the irreversible reactions E. The conversion of glucose to lactate yields two ATP and two NADH

Answer 5

D. The regulated reactions are also the irreversible reactions

Question 6

The generation of metabolic energy from glucose requires glycolysis. What would be the most appropriate mechanism of regulation for this pathway? A. Inhibition of the first irreversible step by glucose B. Inhibition of the first irreversible step by ADP C. Inhibition of the last irreversible step by ADP D. Inhibition of the first irreversible step by ATP E. Inhibition of the first irreversible step by carbon dioxide and water

Answer 6

D. Inhibition of the first irreversible step by ATP

Question 7

In glycolysis glucose-6-phosphate is transformed to fructose-6-phosphate. This reaction is an example of a general type of reaction called a: A. Group transfer reaction B. Oxidation and reduction reaction C. Condensation reaction D. Carbon carbon bond cleavage reaction E. Rearrangement reaction

Answer 7

E. Rearrangement reaction

Question 8

Select from the following the most appropriate statements that apply to glycolysis: A. Occurs in the cytoplasm B. Free energy of glycolysis is mostly exergonic C. There are 12 enzyme catalysed steps D. Five reactions are energy-investing steps

Answer 8

A. Occurs in the cytoplasm B. Free energy of glycolysis is mostly exergonic D. Five reactions are energy-investing steps

Question 9

True or False? Two molecules of ATP are produced per glucose during the hexose stage of glycolysis.

Answer 9

False

Question 10

How many ATP molecules are consumed in glycolysis for every one molecule of glucose? A. 0; ATP is produced, not consumed, by glycolysis B. 1 C. 2 D. 3 E. 4

Answer 10

C. 2

Question 11

The overall △G for glycolysis is -72 kJ/mol in erythrocytes. Which statement below is true? A. The value of △Goʹ is also -72 kJ/mol since the cytosol pH is close to 7. B. The free energy of glycolysis is found as the sum of the standard free energy changes for the individual pathway reactions. C. The negative sign of △G shows that this pathway will proceed toward product (pyruvate) under normal cellular conditions. D. All of the above

Answer 11

C. The negative sign of △G shows that this pathway will proceed toward product (pyruvate) under normal cellular conditions.

Question 12

During glycolysis, isomerization occurs during which of the following reactions? A. Fructose 1,6-bisphosphate → dihydroxyacetone phosphate and glyceraldehyde 3-phosphate B. Fructose 6-phosphate → fructose 1,6-bisphosphate C. Glucose 6- phosphate → fructose 6- phosphate D. Glucose → glucose 6- phosphate

Answer 12

C. Glucose 6- phosphate → fructose 6- phosphate

Question 13

Select from the following the most appropriate statements that apply to glycolysis: A. Four reactions are energy-investing steps B. phosphofructokinase is a major feedback inhibition step C. phosphate is important in the pathway D. occurs in the mitochondria

Answer 13

B. phosphofructokinase is a major feedback inhibition step C. phosphate is important in the pathway

Question 14

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 Chatelierʹs Principle. Which statement below would provide a suitable explanation? 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

Answer 14

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 15

The main pathways of glucose metabolism include: A. Fatty acid degradation B. Urea cycle C. Glycogen synthesis D. Pentose Phosphate pathway

Answer 15

C. Glycogen synthesis D. Pentose Phosphate pathway

Question 16

Seven of the ten reactions in the glycolytic pathway have free energy values close to zero. What does this tell us about those reactions? A. They are near equilibrium reactions. B. They are not control points for pathway regulation. C. They are reversible reactions. D. A, B, and C above E. None of the above

Answer 16

D. A, B, and C above

Question 17

Glycolysis in the erythrocyte produces pyruvate that is further metabolized to: A. CO2. B. lactate. C. glucose. D. hemoglobin. E. ethanol.

Answer 17

B. lactate.

Question 18

Select from the following the most appropriate statements that apply to glycolysis: A. there is a net production of two ATP B. there is production of four ATP C. The reaction is overall endergonic D. NADPH is used in the pathway

Answer 18

B. there is production of four ATP

Question 19

Which of the following statements is not true concerning glycolysis in anaerobic muscle? A. It is an endergonic process. B. It results in synthesis of NADH. C. Fructose 1,6-bisphosphatase is one of the enzymes of the pathway. D. Its rate is slowed by a high [ATP]/[ADP] ratio. E. It results in net synthesis of ATP.

Answer 19

A. It is an endergonic process.

Question 20

The enzyme that catalyzes the conversion of pyruvate to lactate is ________. A. lactate reductase B. pyruvate kinase C. lactoenolpyruvate D. lactate dehydrogenase

Answer 20

D. lactate dehydrogenase

Question 21

Once inside a cell, glucose is rapidly phosphorylated to glucose-6-phosphate. What is one of the main purposes of this initial phosphorylation? A. to keep glucose inside the cell B. to form a high-energy compound C. to activate PFK-1 D. to prevent mutarotation

Answer 21

A. to keep glucose inside the cell

Question 22

Arsenite A. poisons by the same mechanism as arsenate. B. is less toxic than arsenate. C. binds tightly to lipoate sulfur atoms. D. None of the above

Answer 22

C. binds tightly to lipoate sulfur atoms.

Question 23

The GLUT protein principally regulated by insulin is: A. GLUT 1 in red blood cells B. Sodium Dependent glucose transporter (SGLT) in the gut C. GLUT 2 in liver and kidney and pancreatic β-cells D. GLUT 4 in adipose and muscle cells

Answer 23

D. GLUT 4 in adipose and muscle cells

Question 24

Select from the following the most appropriate statements that apply to glycolysis A. Glucose is catabolized to pyruvate B. A net yield of 4 ATP are formed by substrate level phosphorylation. C. The first pathway to extract energy from glucose D. Pyruvate is more oxidized than glucose

Answer 24

A. Glucose is catabolized to pyruvate C. The first pathway to extract energy from glucose D. Pyruvate is more oxidized than glucose

Question 25

Statement: Haemolytic anaemia may result from a defect in one, or more, enzymes of glycolysis Reason: Insufficient NADPH is produced in glycolysis to prevent the damaging effects of oxidising agents

Answer 25

## Footnote Statement is True; Reason is False

Question 26

Select from the following the most appropriate statements that apply to glycolysis: A. The reaction is overall endergonic B. there is production of four ATP C. there is a net production of two ATP D. NADPH is used in the pathway

Answer 26

## Footnote B. there is production of four ATP C. there is a net production of two ATP

Question 27

Compared to pyruvate, the carbon atoms in lactate ________. A. are more reduced B. are more oxidized C. are equally as oxidized D. carry more charge

Answer 27

## Footnote A. are more reduced

Question 28

Select from the following the most appropriate statements that apply to glycolysis: A. Glucose is anabolised to pyruvate B. There are 10 enzyme catalysed steps C. aldolase is a major regulatory enzyme D. It is only an anaerobic pathway

Answer 28

## Footnote B. There are 10 enzyme catalysed steps

Question 29

The glycolytic pathway oxidizes glucose to two molecules of pyruvate and also produces a net of two molecules of ATP. ATP allosterically inhibits the enzyme, PFK-1, that catalyzes the third step of glycolysis. This is an example of ________. A. feed-forward activation B. feedback inhibition C. negative cooperativity D. competitive inhibition

Answer 29

## Footnote B. feedback inhibition

Question 30

True or False? Two molecules of ATP are consumed per glucose during the triose stage of glycolysis

Answer 30

## Footnote False

Question 31

Glucose is the major fuel of most organisms it's benefits include: A. an enthalpy = -2864 kJ/mol B. a free energy of oxidation = -2864 kJ/mol C. supplying carbon for other metabolites D. small molecule with no polar functional groups

Answer 31

## Footnote B. a free energy of oxidation = -2864 kJ/mol C. supplying carbon for other metabolites

Question 32

Under what situation might lactic acidosis occur? A. Lactate dehydrogenase is inactive. B. Transport of glucose into cells is accelerated. C. Oxygen supply to tissues is inadequate. D. PFK-1 is over-activated.

Answer 32

## Footnote C. Oxygen supply to tissues is inadequate.

Question 33

The main pathways of glucose metabolism include: A. Glycolysis B. Glycogenolysis C. Tricarboxylic acid cycle D. Ketone body degradation

Answer 33

## Footnote A. Glycolysis C. Tricarboxylic acid cycle

Question 34

Glycolysis has the largest flux of carbon and this means that there is a: A. high flow rate of glucose through gluconeogenesis B. high flow rate of carbon through glycolysis C. greater flexibility of carbon transport D. large amount of carbon at any one time in the cell

Answer 34

## Footnote B. high flow rate of carbon through glycolysis

Question 35

In the presence of arsenate poisoning 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

Answer 35

## Footnote E. None of the above

Question 36

In some diabetic patients, glucose increases disproportionately and is unresponsive to an insulin challenge; under these conditions, how would oneʹs liver normally respond? A. phosphorylating glucose for entry into the glycolytic pathway B. saturating glucokinase with glucose C. phosphorylating glucose for entry into the glycogen synthesis pathway D. A and B only E. A and C only

Answer 36

## Footnote E. A and C only

Question 37

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? 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

Answer 37

## Footnote B. Hexokinases I, II and III are catalyzing at their maximum rate, but glucokinase can still respond to increases in blood glucose levels

Question 38

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: A. oxaloacetate → malate B. pyruvate → lactate C. dihydroxyacetone phosphate → glycerol 3-phosphate D. isocitrate → α-ketoglutarate E. glucose 6-phosphate → fructose 6-phosphate

Answer 38

## Footnote B. pyruvate → lactate