BCCB2000 Lecture 17 Questions

Question 1

In the gluconeogenesis practical you used a Krebs Ringer Bicarbonate buffer. Choose the reactions that best describes the action of this buffer when: i) Incubated with an atmosphere of carbogen (5% CO2 and 95% O2) ii) Cells release acid during metabolism iii) Cells release CO2 during metabolism

Answer 1

i) CO2 + H2O —> H2CO3 —> HCO3- + H+ ii) CO2 + H2O H2CO3 —> HCO3- + H+

Question 2

Choose from the following list the molecule that would not be glucogenic in humans. A. succinate B. glutamate C. acetyl CoA D. pyruvate E. succinyl CoA

Answer 2

C. acetyl CoA

Question 3

A ‘shuttle mechanism’ is needed to transfer malate from the mitochondria to the cytosol. This particular shuttle mechanism allows: A. a bypass reaction of glycolysis B. oxaloacetate to be regenerated in the cytosol C. transport of metabolites mediated by membrane proteins D. simple diffusion of metabolites across the membrane

Answer 3

B. oxaloacetate to be regenerated in the cytosol C. transport of metabolites mediated by membrane proteins

Question 4

Which of the following reactions is unique to gluconeogenesis? A. Lactate to pyruvate; phosphoenolpyruvate to pyruvate B. 1,3 bis-phosphoglycerate to 3-phosphoglycerate C. glucose-6-phosphate to fructose 6-phosphate D. oxaloacetate to phosphoenolpyruvate

Answer 4

D. oxaloacetate to phosphoenolpyruvate

Question 5

The Cori cycle: A. produces NAD+ in the liver during gluconeogenesis B. produces NADH in liver during gluconeogenesis C. has a reciprocal transfer of glucose and alanine between muscle and liver D. has a reciprocal transfer of glucose and lactate between muscle and liver

Answer 5

A. produces NAD+ in the liver during gluconeogenesis D. has a reciprocal transfer of glucose and lactate between muscle and liver

Question 6

In one of your practicals you explored the gluconeogenic potential of various substrates in tissue slices. The experiment used 2.5ml of a glucose oxidase reagent which was added to 0.5ml of the standard or sample (containing 0.3M percholoric acid). The reagent was comprised of the following: 0.2% w/v benzoic acid (preservative) 0.01% 4-amino antipyrene, 0.15% p-hydroxybenzoic acid, 4 units/mL glucose oxidase, 1.25 units/mL peroxidase in 0.5M Tris-phosphate buffer, pH 7.2. A. buffer the acids present in the reaction mixture B. maintain pH of reaction mixture for enzyme glucose oxidase C. account for dilution when 2.5ml is added to 0.5ml D. provide excess of substrate for reaction E. all of the above

Answer 6

E. all of the above

Question 7

The activity of the gluconeogenic pathway can be increased by the following: A. increase in ATP B. increase in AMP C. increase in fructose 2,6 bisphosphate D. increase in citrate E. increase in acetyl CoA F. increase in insulin G. increase in glucagon H. fasting I. fed

Answer 7

A. increase in ATP D. increase in citrate E. increase in acetyl CoA G. increase in glucagon H. fasting

Question 8

In ruminants, microorganisms produce propionate. The three-carbon acid must be converted to ________ before entering the gluconeogenesis pathway. A. acetyl CoA B. lactate C. citric acid D. succincyl CoA

Answer 8

D. succincyl CoA

Question 9

When intermediates of the TCA cycle are removed (eg. for biosynthetic reactions) this process is known as cataplerosis. When intermediates for the TCA cycel are replaced this is called anaplerosis. Which of the following would be an example of an enzyme that contributes to anaplerosis of the TCA cycle? A. phosphoenolpyruvate carboxykinase (PEPCK) B. pyruvate carboxylase C. glutamate dehydrogenase D. aspartate aminotransferase (AST or GOT or SGOT)

Answer 9

B. pyruvate carboxylase

Question 10

Which of the following is true about gluconeogenesis? A. The gluconeogenesis pathway is the glycolysis pathway running in the opposite direction. B. In mammals, gluconeogenesis occurs predominately in the liver. C. Plants do not undergo gluconeogenesis. D. Gluconeogenesis is the pathway by which glucose is converted to glycogen.

Answer 10

B. In mammals, gluconeogenesis occurs predominately in the liver.

Question 11

Acetyl CoA produced from fatty acid oxidation is essential for gluconeogenesis. Why? A. Acetyl CoA inhibits pyruvate dehydrogenase B. Acetyl CoA activates pyruvate carboxylase C. Acetyl CoA is a substrate for gluconeogenesis D. A and B E. A and C F. B and C G. None of the above

Answer 11

D. A and B

Question 12

Which of the following substrates cannot contribute to net gluconeogenesis in mammalian liver? A. palmitate B. α-ketoglutarate C. alanine D. pyruvate E. glutamate

Answer 12

A. palmitate

Question 13

The conversion of two molecules of pyruvate to one molecule of glucose requires the net input of how much of the following compounds? A. 4 ATP, 2GTP, and 2 NADH B. 6 ATP, 2 GTP, and 4 NADH C. 2 ATP, 1 GTP, and 2 NADH D. 8 ATP, 1 GTP, and 2 NADH E. 4 ATP, 2 GTP, and 4 NADH

Answer 13

A. 4 ATP, 2GTP, and 2 NADH

Question 14

The glucose-alanine cycle: A. transfers glucose to the liver B. transfers ammonium to the muscle C. transfers ammonium to the liver D. transfers glucose to the muscle

Answer 14

C. transfers ammonium to the liver D. transfers glucose to the muscle

Question 15

During prolonged starvation in a human the nutrient pools will decline in the order (where the leftmost pool is used up first): A. Adipose fat - Muscle protein - Muscle glycogen - Liver glycogen B. Muscle protein - Liver glycogen - Muscle glycogen - Adipose fat C. Muscle glycogen - Liver glycogen - Adipose fat - Muscle protein D. Liver glycogen - Muscle glycogen - Muscle protein - Adipose fat

Answer 15

D. Liver glycogen - Muscle glycogen - Muscle protein - Adipose fat

Question 16

Gluconeogenesis can be a source of glucose during: A. normal metabolism B. prolonged exercise C. starvation D. fasting

Answer 16

A. normal metabolism B. prolonged exercise C. starvation D. fasting

Question 17

The glucose-alanine cycle is: A. an intratissue cycling of metabolites B. a transfer of metabolites involving two tissues C. an intertissue cycling of metabolites D. a transfer of metabolites involving three tissues

Answer 17

C. an intertissue cycling of metabolites D. a transfer of metabolites involving three tissues

Question 18

Statement: Gluconeogenesis is not a reversal of glycolysis Reason: There are three reversible reactions of glycolysis

Answer 18

Statement is True; Reason is False

Question 19

A enzyme of gluconeogenesis that is different from the enzymes of glycolysis is: A. phosphofructokinase 1 B. glucose 6-phosphatase C. pyruvate kinase D. glucokinase

Answer 19

B. glucose 6-phosphatase

Question 20

When a Muslim person observes Ramadan they usually fast from sunrise to sunset every day for about a month. This could be from about 5.30am to 7.30pm every day (depending upon the time of sunrise and sunset). What would be the main source of blood glucose toward the end of this daily fast? A. Muscle glycogen B. Liver glycogen C. Gluconeogenesis from amino acids D. Gluconeogenesis from lactate E. Dietary glucose

Answer 20

B. Liver glycogen

Question 21

The interconversion of which pair of substrates is used as a regulatory point in gluconeogenesis? A. lactate and pyruvate B. dihydroxyacetone phosphate and glyceraldehyde-3-phosphate C. fructose 1,6-bisphosphate and fructose 6-phosphate D. phosphoenolpyruvate and 2-phosphoglycerate

Answer 21

C. fructose 1,6-bisphosphate and fructose 6-phosphate

Question 22

Gluconeogenesis uses the same enzymatic reactions of glycolysis except for the ________. A. 3 irreversible reactions in glycolysis B. pyruvate kinase catalyzed step C. 2 irreversible reactions in glycolysis D. 4 irreversible reactions in glycolysis

Answer 22

A. 3 irreversible reactions in glycolysis

Question 23

The Cori cycle: A. uses NADH in the muscle when pruvate is converted to lactate B. produce NADH in the muscle when pruvate is converted to lactate C. uses NADH in liver during when lactate is converted to pyruvate D. produces NADH in the liver when lactate is converted to pyruvate

Answer 23

A. uses NADH in the muscle when pruvate is converted to lactate D. produces NADH in the liver when lactate is converted to pyruvate

Question 24

Glycerol is converted to ________ when it is used for gluconeogenesis. A. dihydroxyacetone phosphate B. phosphoenolpyruvate C. oxaloacetate D. 3-phosphoglycerate

Answer 24

A. dihydroxyacetone phosphate

Question 25

The synthesis of glucose from pyruvate by gluconeogenesis: A. occurs exclusively in the cytosol B. occurs exclusively in the mitochondria C. requires the participation of biotin D. involves lactate as an intermediate E. requires the oxidation of FAD

Answer 25

## Footnote C. requires the participation of biotin

Question 26

Label each of the following as occuring either in the Cori Cycle (type CC), Glucose-Alanine cycle (type GAC), or both (type B): Transamination in muscle _____ [a] Deamination in liver _____ [b] Transfer of glucose from liver to muscle _____ [c] Transfer of carbon (in the form of alanine, lactate, or glucose) between muscle and liver ______ [d] Transfer of ammonium (in the form of alanine) from muscle to liver [e] Net production of ATP in Muscle [f] Net use of ATP in liver [g] Transfer of lactate from muscle to liver [h]

Answer 26

## Footnote a GAC b GAC c B d B e GAC f B g B h CC

Question 27

Gluconeogenesis is the: A. synthesis of glycogen from pyruvate B. synthesis of glycogen from fructose C. synthesis of glucose from pyruvate D. synthesis of glucose from fructose

Answer 27

## Footnote C. synthesis of glucose from pyruvate

Question 28

Glucose that is not part of a human diet may be provided by degradation of _____________________ A. glycogen B. starch. C. dextrin. D. A and B E. A, B and C

Answer 28

## Footnote A. glycogen

Question 29

Statement: Gluconeogenesis is the production of new (de novo) glucose. Reason: Monosaccharides can readily be converted to glucose

Answer 29

## Footnote Statement is True; Reason is True; the reason is an incorrect explanation of the statement

Question 30

In the Cori cycle, gluconeogenesis occurs in ________ and glycolysis in ________. A. liver; muscle B. liver; liver C. muscle; muscle D. muscle; liver

Answer 30

## Footnote A. liver; muscle

Question 31

Fructose 2,6 bisphosphate is primarily considered an: A. intermediate of glycolysis B. allosteric activator C. allosteric inhibitor D. intermediate of glycogenolysis

Answer 31

## Footnote B. allosteric activator

Question 32

Glycerol can act as a precursor for gluconeogenesis because it: A. can be converted into an intermediate of glycogenesis B. stimulates the production of a glycolytic enzyme C. stimulates the production of a gluconeogenic enzyme D. can be converted into an intermediate of glycolysis

Answer 32

## Footnote D. can be converted into an intermediate of glycolysis

Question 33

Gluconeogenesis is the ________. A. result of amylase activity B. formation of glycogen C. formation of starches D. formation of glucose from simple two and three-carbon precursors E. formation of glucose from other carbohydrates

Answer 33

## Footnote D. formation of glucose from simple two and three-carbon precursors

Question 34

Which one of the following statements concerning gluconeogenesis is correct? A. It occurs in muscle B. It is stimulated by fructose 2,6-bisphosphate C. It is inhibited by elevated levels of acetyl CoA D. It is important in maintaining blood glucose during the normal overnight fast E. It uses carbon skeletons provided by degradation of fatty acids

Answer 34

## Footnote D. It is important in maintaining blood glucose during the normal overnight fast

Question 35

Biotin is an essential nutrient (otherwise known as Vitamin B7) for the action of pyruvate carboxylase this means that: A. Biotin is required for the synthesis of phosphoenolpyruvate B. Biotin can be synthesised by the cells C. Biotin required for the synthesis of oxaloacetate D. Biotin can only be obtained from the diet

Answer 35

## Footnote C. Biotin required for the synthesis of oxaloacetate D. Biotin can only be obtained from the diet

Question 36

Extremely hard and prolonged physical work can lead to a pronounced fall in blood sugar. Marathon runners, skiers and others that press their bodies to maximal performance sometimes collapse before the finish line. The most likely reason for this collapse is: A. Insufficient liver gluconeogenesis C. Dehydration E. Increase in adrenalin B. Exhaustion of glycogen stores D. Loss of electrolytes

Answer 36

## Footnote A. Insufficient liver gluconeogenesis

Question 37

Which of the following is not usually considered a precursor for gluconeogenesis? A. alanine B. glycerol C. oxaloacetate D. lactate E. ethanol

Answer 37

## Footnote E. ethanol

Question 38

The sequence of glucose oxidation to lactate in peripheral tissues, delivery of lactate to the liver, formation of glucose from lactate in the liver, and delivery of glucose back to peripheral tissues is known as the ________. A. glyoxylate cycle B. Kreb's cycle C. Cori cycle D. gluconeogenesis cycle

Answer 38

## Footnote C. Cori cycle

Question 39

Gluconeogenesis is: A. a source of blood glucose B. takes place only in erythrocytes C. takes place only in muscle D. source of carbon for other biomolecules E. maintains blood glucose

Answer 39

## Footnote A. a source of blood glucose D. source of carbon for other biomolecules E. maintains blood glucose

Question 40

Up to about 75% of the glucose generated by gluconeogenesis is used by: A. the liver B. the kidney cortex C. the brain D. the skeletal muscles

Answer 40

## Footnote C. the brain

Question 41

Statement: Four gluconegenic reactions circumvent some reactions of glycolysis. Reason: There are three irreversible reactions of glycolysis

Answer 41

## Footnote Statement is True; Reason is True; the reason is a correct explanation of the statement

Question 42

A enzyme of gluconeogenesis that is different from the enzymes of glycolysis is: A. glucokinase B. phosphofructokinase C. phosphoenolpyruvate carboxykinase D. pyruvate kinase

Answer 42

## Footnote C. phosphoenolpyruvate carboxykinase

Question 43

Any compound that can be converted to ________ can be a precursor for gluconeogenesis. A. citrate B. pyruvate C. oxaloacetate D. A or B E. A or C F. B or C

Answer 43

## Footnote F. B or C

Question 44

Fructose 2,6-bisphosphate ________ glycolysis while it ________ gluconeogenesis. A. stimulates; stimulates B. stimulates; inhibits C. inhibits; stimulates D. inhibits; inhibits

Answer 44

## Footnote B. stimulates; inhibits

Question 45

Statement: The overall standard Free Energy of gluconeogenesis is -38kJ/mol Reason: All reactions in the gluconeogenic pathway are spontaneous.

Answer 45

## Footnote Statement is True; Reason is False

Question 46

The Cori cycle: A. transfers glucose to the liver B. transfers ammonium to the muscle C. transfers lactate to the liver D. transfers alanine to the liver

Answer 46

## Footnote C. transfers lactate to the liver