Deck 8: Carbohydrate Metabolism

Question 1

Both glycogenesis and glycogenolysis are controlled primarily by the interplay between the two hormones insulin and __________.

A) glycogen synthetase
B) glucagon
C) fructose kinase
D) glucose hydrolyase
E) pentose kinase

Answer 1

B

Question 2

Hexokinase D is found in the __________.

A) kidney
B) liver
C) heart
D) muscle
E) intestine

Answer 2

B

Question 3

An enzyme family called the __________ catalyzes the phosphorylation of hexoses in the body.

A) hexolysases
B) phosphorolyases
C) hexokinases
D) glucokinases
E) phosphofructokinases

Answer 3

C

Question 4

The conversion of glucose-1-phosphate to UDP-glucose has a G^0' near zero. Which of the following reactions is coupled with the previous reaction to drive it to completion?

A) Hydrolysis of PP_i
B) Hydrolysis of ATP
C) Hydrolysis of ADP
D) Hydrolysis of UDP
E) Hydrolysis of UTP

Question 5

Which of the following is required for the conversion of UDP-glucose to glycogen?

A) Glycogen synthase
B) Branching enzyme
C) Glucose phosphorylase
D) Debranching enzyme
E) Both A and B are correct.

Question 6

A glycogen molecule that has been degraded to its branch points is called __________.

A) dextrin
B) glucose
C) amylose
D) limit dextrin
E) Both A and B are correct.

Question 7

Regulation of glycolysis involves all of the following except __________.

A) insulin
B) glucagon
C) SREBP1c
D) AMPK
E) None of the above are correct.

Question 8

The binding of insulin to receptors on the surface of muscle cells stimulates which of the following processes?

A) Glycogenolysis
B) Glycogenesis
C) Release of ATP
D) Formation of cyclic AMP
E) Release of glucagon

Question 9

Under stressful conditions epinephrine is released from the adrenal medulla. The release of epinephrine has which of the following effects on glucose metabolism?

A) Glycogenolysis is stimulated.
B) Glycogenesis is inhibited.
C) Adenylate cyclase is activated.
D) Both A and B are correct.
E) All the above are correct.

Question 10

Phosphorylase kinase __________.

A) converts inactive phosphorylase to active phosphorylase
B) converts active phosphorylase to inactive phosphorylase
C) phosphorylates glycogen synthase
D) converts ADP to ATP
E) Both B and C are correct.

Question 11

Cori's disease is caused by __________.

A) lack of insulin
B) lack of phosphorylase b
C) lack of glucagons
D) a deficiency of debranching enzyme
E) deficient chromium receptors on the cell surface

Question 12

Which of the following activates phosphoprotein phosphatase?

A) Insulin
B) Epinephrine
C) Glucagon
D) ATP
E) Both A and B are correct.

Question 13

Glucose-6-phosphate is a substrate in which of the following processes?

A) Gluconeogenesis
B) Glycolysis
C) Photosynthesis
D) Glycogenolysis
E) Both A and B are correct.

Question 14

Fructose-2,6-bisphosphate __________.

A) is an indicator of high cellular glucose concentration
B) is formed by PFK-1
C) activates aldolase
D) Both A and B are correct.
E) All of the above are correct.

Question 15

The Embden-Myerhof pathway is also referred to as __________.

A) gluconeogenesis
B) glycogenolysis
C) glycolysis
D) glycogenesis
E) citric acid cycle

Question 16

In glycolysis __________ moles of ATP are produced per mole of glucose consumed.

A) one
B) two
C) three
D) four
E) five

Question 17

In glycolysis __________ moles of NADH are produced per mole of glucose consumed.

A) one
B) two
C) three
D) four
E) five

Question 18

The presence of which of the following molecules indicates that the cell has sufficient energy reserves?

A) ATP
B) Citrate
C) ADP
D) Fructose-1,6-biphosphate
E) Both A and B are correct.

Question 19

Which of the following enzymes is an oxidoreductase?

A) Aldolase
B) Triose phosphate isomerase
C) Glyceraldehyde-3-phosphate dehdyrogenase
D) Phosphofructokinase
E) Phosphoglucoisomerase

Question 20

The first reaction in the oxidative phase of the pentose phosphate pathway is catalyzed by __________.

A) ribulose-5-phosphate dehydrogenase
B) transketolase
C) glucose-6-phosphatase
D) glucose-6-phosphate dehydrogenase
E) hexokinase

Question 21

Which of the following enzymes catalyzes an irreversible process?

A) Pyruvate kinase
B) Aldolase
C) Enolase
D) Phosphoglycerate mutase
E) Glyceraldehyde-3-phosphate dehydrogenase

Question 22

In anaerobic organisms pyruvate is used to regenerate cellular __________.

A) NADP⁺
B) FADH
C) FAD
D) NAD⁺
E) ADP

Question 23

Allosteric regulation of which of the following enzymes is important in the regulation of glycolysis?

A) Hexokinase
B) PFK-1
C) Pyruvate kinase
D) Both A and C are correct.
E) All of the above are correct.

Question 24

Gluconeogenesis occurs primarily in the __________.

A) brain
B) muscle
C) liver
D) heart
E) pancreas

Question 25

Which of the following molecules can be used to synthesize glucose via gluconeogenesis?

A) Lactate
B) Pyruvate
C) Glycerol
D) Keto acids
E) All of the above are correct.

Question 26

Which of the following is the most important glucogenic amino acid?

A) Aspartate
B) Alanine
C) Glycine
D) Glutamate
E) All are equally important.

Question 27

Gluconeogenesis is stimulated by high concentrations of which of the following compounds?

A) Lactate
B) Glycerol
C) Amino acid
D) Both A and B are correct
E) All of the above are correct

Question 28

Which of the following is an oxidizing agent in fermentation?

A) Lactate
B) Glucose
C) NADH
D) Pyruvate
E) ADP

Question 29

In addition to glucose which of the following sugars are important in the human diet?

A) Fructose
B) Galactose
C) Mannose
D) Sucrose
E) Both A and D are correct.

Question 30

Intermediates in the nonoxidative phase of the pentose phosphate pathway include all of the following except __________.

A) dihydroxyacetone phosphate
B) sedoheptulose-7-phosphate
C) fructose-6-phosphate
D) xylulose-5-phosphate
E) erythrose-4-phosphate

Question 31

The use of a highly exergonic reaction in the beginning of a catabolic pathway is referred to as __________.

A) bioactivation
B) turbo design
C) activation
D) glycolysis
E) Both A and C are correct.

Question 32

Aldol cleavage of which of the following sugars will produce one mole each of dihydroxyacetone and glyceraldehyde?

A) Fructose
B) Glucose
C) Ribose
D) Maltose
E) Trehalose

Question 33

Which of the following is a second messenger in glycogenolysis?

A) Glucagon
B) Insulin
C) Glucose
D) ATP
E) cAMP

Question 34

In animals excess glucose is converted into its storage form, __________.

A) starch
B) chitin
C) glycogen
D) amylose
E) amylopectin

Question 35

The major carbohydrate fuel for most organisms is __________.

A) glucose
B) fructose
C) ribose
D) sucrose
E) All of the above are correct.

Question 36

Which of the following enzymes is not required in gluconeogenesis?

A) Phosphoenolpyruvate carboxykinase
B) Phosphofructokinase
C) Pyruvate kinase
D) Fructose-1,6-bisphosphatase
E) Pyruvate carboxylase

Question 37

The final product of glycolysis is __________.

A) dihydroxyacetone phosphate
B) pyruvate
C) ethanol
D) acetyl-CoA
E) acetaldehyde

Question 38

The principal products of the pentose phosphate pathway include __________.

A) NADH
B) NADPH
C) ATP
D) ribose-5-phosphate
E) Both B and D are correct.

Question 39

Flux of which of the following sugars into the glycolytic pathway is essentially unregulated.

A) Glucose
B) Fructose
C) Glucose-1-phosphate
D) Both A and C are correct
E) None of the above are correct

Question 40

Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate has two purposes. One is the commitment of the molecule to glycolysis; the second is __________.

A) raising the free energy of the system
B) making possible the formation of a second mole of ATP
C) preventing the cleavage products of the next step from diffusing out of the cell
D) preventing the reverse reaction
E) enolization of the product

Question 41

Which of the following enzymes will catalyze the first committed step in glycolysis?

A) Phosphofructoisomerase
B) Aldolase
C) Triose phosphate isomerase
D) Phosphofructokinase 1
E) Phosphoglucooisomerase

Question 42

The Crabtree effect in yeast is __________.

A) fermentation of glucose
B) repression of aerobic metabolism by glucose
C) repression of glycolysis by oxygen
D) repression of glucose metabolism by ethyl alcohol
E) fermentation of ethyl alcohol

Question 43

The Pasteur effect is __________.

A) fermentation of glucose
B) repression of aerobic metabolism by glucose
C) repression of glycolysis by oxygen
D) repression of glucose metabolism by ethyl alcohol
E) fermentation of ethyl alcohol

Question 44

A diauxic shift is __________.

A) a significant change in gene expression
B) shifting from aerobic to anerobic respiration
C) shifting from anerobic to aerobic respiration
D) change in composition of microbes in a sample
E) change in the amount of ATP used to ferment glucose

Question 45

The phosphorylation of glucose when it enters a cell accomplishes which of the following?

A) Makes the glucose more water soluble
B) Prevents back diffusion out of the cell
C) Isomerize the glucose
D) Activates the glucose for further reaction
E) Both B and D are correct.

Question 46

Which of the following compounds is an end product of anaerobic respiration?

A) Carbon dioxide
B) Ethanol
C) Water
D) Glycogen
E) Acetaldehyde

Question 47

In which reaction in glycolysis does a dehydration occur?

Question 48

Upon entering a cell, glucose is phosphorylated. Give two reasons why this reaction is required.

Question 49

What reaction is catalyzed by aldolase?

Question 50

What reaction is catalyzed by hexokinase?

Question 51

What reaction is catalyzed by phosphoglucomutase?

Question 52

Suggest a reason why glycolysis produces NADH and the pentose phosphate pathway produces NADPH.

Question 53

What is the principle reason that organisms such as yeast produce alcohol?

Question 54

What happens to pyruvate under anaerobic conditions in aerobic cells?

Question 55

Glycolysis occurs in two stages. Describe what is accomplished in each stage.

Question 56

Compare the entry-level substrates, products and metabolic purposes of glycolysis and gluconeogenesis.

Question 57

Why is severe hypoglycemia so dangerous?

Question 58

Describe the effect of insulin and glucagon on blood glucose.

Question 59

Describe the Cori cycle; what is its physiological function?

Question 60

Describe the effects of insulin and glucagon on glycogen metabolism.

Question 61

What cell types produce insulin, glucagon, epinephrine, and cortisol?

Question 62

Describe the different functions of glycogen in muscle and liver.

Question 63

Glycogen synthesis requires a short primer chain. Explain how new glycogen molecules are synthesized given this limitation.

Question 64

Why does PEP have such a high phosphoryl group transfer potential?

Question 65

In aerobic metabolism oxygen is the ultimate oxidizing agent (electron acceptor). What is the oxidizing agent in anaerobic fermentation?

Question 66

How does phosphorylation increase the reactivity of glucose?

Question 67

Explain and contrast the Pasteur and Crabtree effects.

Question 68

Explain the role of glycogenin in glycogen synthesis.

Question 69

Describe the physiological condition that activates gluconeogenesis. What prevents competition between gluconeogenesis and glycolysis?

Question 70

An individual has a genetic condition that prevents the production of glucokinase. Following a carbohydrate meal do you expect blood glucose levels to be high, low or about normal? What organ accumulates glycogen under these circumstances?

Question 71

Why is fructose metabolized more rapidly than glucose?

Question 72

Why is it important that gluconeogenesis not be the exact reverse of glycolysis?

Question 73

Severe dieting results in both the reduction of fat stores and the loss of muscle mass. Trace the conversion of muscle protein to glucose production.

Question 74

Both glycogen and triacylglycerols are energy sources used by the body. Suggest a reason why both are needed.

Question 75

List the three principle hormones that regulate glucose metabolism. Briefly explain the effects these molecules have on carbohydrate metabolism.