BCCB2000 Lecture 18 Questions

Question 1

The antioxidant enzyme systems used by cells to combat reactive oxygen species include: A. superoxide mutase B. glutathione dehydrogenase C. glutathione peroxidase D. catalase

Answer 1

C. glutathione peroxidase D. catalase

Question 2

The pentose phosphate pathway in association with the glycolytic pathway can: A. use carbon dioxide B. generate ATP C. generate carbon dioxide D. use ATP

Answer 2

B. generate ATP C. generate carbon dioxide D. use ATP

Question 3

The pentose phosphate pathway is useful for the cell because: A. ATP can be produced B. it can result in DNA or RNA degradation C. glycogen can usually be produced D. it can result in DNA or RNA synthesis

Answer 3

A. ATP can be produced D. it can result in DNA or RNA synthesis

Question 4

The pentose phosphate pathway is useful for the cell because: A. prevents the use of separate pathways for five-carbon and six-carbon sugars B. five-carbon sugars may be replenished from NADPH C. one pathway is needed for the interconversion of five-carbon sugars to six-carbon sugars D. metabolism can be adjusted to appropriately distribute carbon dioxide for information or energy needs

Answer 4

A. prevents the use of separate pathways for five-carbon and six-carbon sugars C. one pathway is needed for the interconversion of five-carbon sugars to six-carbon sugars

Question 5

Statement: Most cells generate carbon dioxide from metabolic reactions that occur in mitochondria. Red blood cells (erythrocytes) do not contain any mitochondria. Consequence: Red blood cells will not be able to generate any carbon dioxide from metabolic reactions.

Answer 5

Statement is True; Consequence is False

Question 6

Which of the following tissues has a low activity of (or low flux through) the pentose phosphate pathway? A. Liver B. Erythrocytes C. Adrenal cortex D. Skeletal muscle

Answer 6

D. Skeletal muscle

Question 7

Glutathione reductase requires ___________ for its reducing activity. A. reduced glutathione B. NADPH C. NAD+ D. hydrogen peroxide =

Answer 7

B. NADPH

Question 8

A beneficial effect of a human with glucose 6-phosphate dehydrogenase (G6PD) deficiency is that it could provide some resistance to the detrimental effects of the malarial parasite Plasmodium falciparum. This is because: A. the parasite is insensitive to reactive oxygen species B. the enzyme catalyses the production of NADPH C. the enzyme catalyses the production of reactive oxygen species D. the parasite is sensitive to reactive oxygen species

Answer 8

B. the enzyme catalyses the production of NADPH D. the parasite is sensitive to reactive oxygen species

Question 9

The enzymes involved in the elimination of reactive oxygen species (ROS) in the cell and use glutathione as an intermediary are: A. catalase B. glutathione peroxidase C. glutathione reductase D. glutathione dismutase

Answer 9

B. glutathione peroxidase C. glutathione reductase

Question 10

Catalase and glutathione peroxidase are similar in that they both catalyse the transformation of: A. oxygen to water B. superoxide to hydrogen peroxide C. hydrogen peroxide to water D. hydrogen peroxide to oxygen

Answer 10

C. hydrogen peroxide to water

Question 11

NADPH can be used to: A. convert pyruvate to lactate B. remove reactive oxygen species (ROS) C. convert lactate to pyruvate D. generate reactive oxygen species (ROS)

Answer 11

B. remove reactive oxygen species (ROS) D. generate reactive oxygen species (ROS)

Question 12

The major regulatory step of the pentose phosphate pathway is catalyzed by which enzyme? A. transaldolase B. phosphofructokinase-1 C. glucose 6-phosphate dehydrogenase D. ribose 5-phosphate isomerase

Answer 12

C. glucose 6-phosphate dehydrogenase

Question 13

Glutathione peroxidase, catalase, and superoxide dismutase are all enzymes that have a role in A. amino acid oxidation B. pentose phosphate pathway C. TCA cycle D. metabolism of reactive oxygen species

Answer 13

D. metabolism of reactive oxygen species

Question 14

True or False? The pentose phosphate pathway does not need to use any energy in the form of ATP

Answer 14

False

Question 15

True or False? The cytochrome P450 monooxygenase enzymes are given the name ‘P450’ to indicate that a particular form of the enzyme absorbs at a wavelength of about 450nm.

Answer 15

True

Question 16

True or False? The non-oxidative part of the pentose phosphate pathway is useful because it allows interconversion of five-carbon and six-carbon sugars.

Answer 16

True

Question 17

When cells need more ribose 5-phosphate for the synthesis of DNA they can generate it from glucose 6-phosphate via reactions of glycolysis and the pentose phosphate pathway. This series of interrelated reactions can be described by an overall reaction as follows: 5 glucose 6-phosphate + ATP = 6 Ribose 5-phosphate + ADP + H+ This reaction shows that five molecules of glucose 6-phosphate are needed to produce six molecules of ribose 5-phosphate. Which of the following are most likely to contribute to the production of 6 ribose 5-phosphate molecules according the stoichiometry of the overall reaction? Hint: think about carbon atoms. A. 5 fructose 6-phosphate + 1 glyceraldehyde 3-phosphate B. 2 fructose 6-phosphate + 4 glyceraldehyde 3-phosphate C. 3 fructose 6-phosphate + 3 glyceraldehyde 3-phosphate D. 4 fructose 6-phosphate + 2 glyceraldehyde 3-phosphate

Answer 17

D. 4 fructose 6-phosphate + 2 glyceraldehyde 3-phosphate

Question 18

Glutathione is a molecule that has a role in A. amino acid oxidation B. protection against reactive oxygen species C. glycolysis D. TCA cycle

Answer 18

B. protection against reactive oxygen species

Question 19

The cytochrome P450 monooxygenase enzyme system in microsomes is used by the cell to: A. insert one oxygen atom into particular substrate molecules B. remove two oxygen atoms from particular substrate molecules C. insert one oxygen atom into an alcohol D. remove one oxygen atom from particular substrate molecules

Answer 19

A. insert one oxygen atom into particular substrate molecules

Question 20

The symptoms of G6PDH deficiency could be made worse by: A. Malaria B. Antipyretics C. Antioxidants D. Favism

Answer 20

B. Antipyretics D. Favism

Question 21

The pentose phosphate pathway is useful for the cell because: A. carbon in six-carbon sugars may be used for the synthesis of DNA B. intermediates can be ‘fed’ into glycolysis C. two separate pathways are needed for the interconversion of five-carbon sugars to six-carbon sugars D. dietary five carbon sugars can be metabolised

Answer 21

A. carbon in six-carbon sugars may be used for the synthesis of DNA B. intermediates can be ‘fed’ into glycolysis D. dietary five carbon sugars can be metabolised

Question 22

True or False? Rapidly dividing cells generally have a high pentose phosphate pathway activity.

Answer 22

True

Question 23

The oxidative ‘part’ of the pentose phosphate pathway can: A. generate NADPH B. convert a five-carbon sugar phosphate to a six-carbon sugar phosphate C. produce ribose-5-phosphate from glucose 6-phosphate D. produce intermediates for glycolysis from five-carbon sugar phosphates

Answer 23

A. generate NADPH C. produce ribose-5-phosphate from glucose 6-phosphate

Question 24

True or False? Two molecules of NADPH are generated for each molecule of glucose 6-phosphate that enters the pentose phosphate pathway.

Answer 24

True

Question 25

If the NADP+/NADPH ratio decreases then this would probably lead to: A. Decreased production of NADPH B. Increased activity of the pentose phosphate pathway C. Increased production of NADPH D. Decreased activity of the pentose phosphate pathway

Answer 25

## Footnote A. Decreased production of NADPH D. Decreased activity of the pentose phosphate pathway

Question 26

The cytochrome P450 monooxygenase enzyme system in microsomes is used by the cell for: A. adding electrons to alcohol molecules B. removing electrons from alcohol molecules C. hydroxylating particular molecules D. activating or deactivating a drug

Answer 26

## Footnote C. hydroxylating particular molecules D. activating or deactivating a drug

Question 27

Statement: Glutathione consists of glycine and cysteine joined by a bond between the alpha amino group of glycine and the alpha carboxyl group of cysteine. The cysteine is also joined by a bond between the alpha amino group of cysteine and the gamma carboxyl group of glutamate. Consequence: Glutathione is not a tripeptide

Answer 27

## Footnote Statement is True; Consequence is False

Question 28

When cells need more ribose 5-phosphate for the synthesis of DNA they can generate it from glucose 6-phosphate via reactions of glycolysis and the pentose phosphate pathway. This series of interrelated reactions can be described by an *overall reaction* as follows: 5 glucose 6-phosphate + ATP = 6 Ribose 5-phosphate + ADP + H+ As can be seen ATP is used to produce six molecules of ribose 5-phosphate from five molecules of glucose 6-phosphate but which reaction in the scheme of interrelated reactions uses ATP? A. fructose 1,6-bisphosphate to glyceraldehyde 3-phosphate B. glucose to glucose 6-phosphate C. glucose 6-phosphate to 6-phosphogluconate D. fructrose 6-phosphate to fructose 1,6-bisphosphate

Answer 28

## Footnote D. fructrose 6-phosphate to fructose 1,6-bisphosphate

Question 29

Reactive oxygen species can denature haemoglobin and allow inappropriate disulphide bonds to form between haemoglobin molecules. This creates large aggregates of haemoglobin called Heinz bodies which accumulate near the cell membrane. Which of the following likely apply to this particular scenario A. liver cell B. decreased glutathione C. muscle cell D. erythrocyte E. increased glutathione

Answer 29

## Footnote B. decreased glutathione D. erythrocyte

Question 30

Glutathione reductase requires ___________ for its activity. A. hydrogen peroxide B. oxidised glutathione C. NAD+ D. NADH

Answer 30

## Footnote B. oxidised glutathione

Question 31

Statement: The cellular concentration of NADPH is about 70 fold higher than the concentration of NADP+ Consequence: This prevents the oxidation of glucose 6 phosphate.

Answer 31

## Footnote Statement is True; Consequence is True

Question 32

The non-oxidative 'part' of the pentose phosphate pathway can: A. produce ribose-5-phosphate from glucose 6-phosphate B. convert a five-carbon sugar phosphate to a six-carbon sugar phosphate C. produce intermediates for glycolysis from five-carbon sugar phosphates D. generate NADPH

Answer 32

## Footnote B. convert a five-carbon sugar phosphate to a six-carbon sugar phosphate C. produce intermediates for glycolysis from five-carbon sugar phosphates

Question 33

The antioxidant enzyme systems used by cells to combat reactive oxygen species include: A. superoxide dismutase B. glutathione dehydrogenase C. hydrogen diperoxidase D. glutathione permanganase

Answer 33

## Footnote A. superoxide dismutase

Question 34

Which of the following are potential roles of NADPH in the cell: A. Reduction of cytochrome P450 enzymes B. Synthesis of aspartate C. Oxidation of hydrogen peroxide D. Synthesis of cholesterol

Answer 34

## Footnote A. Reduction of cytochrome P450 enzymes D. Synthesis of cholesterol

Question 35

If the NADP+/NADPH ratio increases then this would probably lead to: A. Decreased activity of the pentose phosphate pathway B. Increased production of NADPH C. Increased activity of the pentose phosphate pathway D. Increased production of NADP+

Answer 35

## Footnote B. Increased production of NADPH C. Increased activity of the pentose phosphate pathway

Question 36

The cytochrome P450 system is responsible for A. producing ATP B. detoxifying chemicals C. using reactive oxygen species D. producing NADPH

Answer 36

## Footnote B. detoxifying chemicals

Question 37

Some of the major tissues where the pentose phosphate is active include: adipose tissue, mammary gland, and liver. What possible reason would they have for an active pentose phosphate pathway? production of energy production of lipids production of glycogen production of nucleotides

Answer 37

## Footnote production of lipids

Question 38

The non-oxidative stage of the pentose phosphate pathway ________. A. produces NADPH and releases CO2 B. interconverts five carbon and six carbon sugars C. contains two reactions whose enzymes are allosterically inhibited by NADPH D. consumes four ATP molecules

Answer 38

## Footnote B. interconverts five carbon and six carbon sugars

Question 39

The non-oxidative stage of the pentose phosphate pathway produces substances that are intermediates of ________. A. glycolysis B. the citric acid cycle C. the Cori cycle D. glycogenolysis

Answer 39

## Footnote A. glycolysis