Deck 16: Glycolysis and Gluconeogenesis

Question 1

A potent allosteric activator of liver phosphofructokinase is _____________________, which is produced from fructose-6-phosphate by PFK2.

Answer 1

fructose-2,6-bisphosphate

Question 2

In alcoholic fermentation, the decarboxylation of pyruvate requires a coenzyme that contains the vitamin ______________.

Answer 2

thiamine, or B₁

Question 3

Pancreatic ______________ is the digestive enzyme primarily responsible for the hydrolysis of dietary plant starch.

Answer 3

α-amylase

Question 4

Glycolysis produces a net of ________ moles of ATP per 1 mole of glucose.

Question 5

What transporter is responsible for fructose uptake in the intestine?

A) GLUT1
B) GLUT2
C) GLUT3
D) GLUT4
E) GLUT5

Question 6

Which of the following is an allosteric inhibitor of phosphofructokinase?

A) NADH
B) ATP
C) AMP
D) fructose 1,6-bisphosphate
E) None of the answers is correct.

Question 7

Which of the following conditions results from genetic deficiency of a single transferase enzyme?

A) lactose intolerance
B) galactosemia
C) lactic acidosis
D) hypoglycemia
E) None of the answers is correct.

Question 8

What type of organism cannot survive in the presence of oxygen?

A) obligate anaerobes
B) facultative anaerobes
C) obligate aerobes
D) facultative aerobes
E) None of the answers is correct.

Question 9

The key enzyme that regulates the pace of glycolysis is ____________________.

Question 10

The formation of ATP is due to direct transfer of a phosphoryl group and is called ___________________.

Question 11

Which of the following is an allosteric inhibitor of gluconeogenesis?

A) NADH
B) ATP
C) AMP
D) fructose 6-phosphate
E) phosphoenolpyruvate

Question 12

The ________________ cycle refers to the metabolic reactions by which glucose is converted into lactate in skeletal muscle, and then lactate is converted back into glucose in the liver.

Question 13

The catalytic mechanism of the isomerization of a ketose into an aldose proceeds through an _________________ intermediate.

Question 14

What nutrient is required for the carboxylation of pyruvate in humans?

A) biotin
B) thiamine
C) riboflavin
D) niacin
E) folic acid

Question 15

The Embden Meyerhof pathway is also known as _____.

A) pentose phosphate pathway
B) glycolysis
C) citric acid cycle
D) gluconeogenesis
E) None of the answers is correct.

Question 16

The first step in gluconeogenesis is the ___________________ of pyruvate to form oxaloacetate.

Question 17

What is the name of the pathway that converts noncarbohydrate molecules into glucose?

A) pentose phosphate pathway
B) glycogenolysis
C) citric acid cycle
D) gluconeogenesis
E) None of the answers is correct.

Question 18

Which of the following must be regenerated for glycolysis to proceed?

A) pyruvate
B) ATP
C) NAD⁺
D) UDP-glucose
E) All of the answers are correct.

Question 19

In the absence of oxygen, _____________________ increases the expression of most glycolytic enzymes and the glucose transporters GLUT1 and GLUT3.

Question 20

Which of the following intermediates is needed for the conversion of galactose into glucose by reacting with galactose 1-phosphate?

A) glucose 1-phosphate
B) fructose 6-phosphate
C) glucose 6-phosphate
D) UDP-galactose
E) UDP-glucose

Question 21

What is a common mechanistic feature of kinases?

A) Phosphoryl groups are transferred from a substrate with high phosphoryl-transfer potential to AMP.
B) Binding of substrate causes a large conformation change that results in cleft closing.
C) All phosphorylation reactions are specific for monosaccharides.
D) Phosphorylation always uses ATP as a substrate.
E) None of the answers is correct.

Question 22

What is the function of glyceraldehyde 3-phosphate dehydrogenase?

A) oxidation of an aldehyde by NAD⁺ and formation of acyl-phosphate
B) oxidation of an alcohol to an aldehyde by NAD⁺
C) dehydration and dephosphorylation of GAP
D) hydrolysis of GAP
E) removal of the 3-phosphoryl-group from GAP

Question 23

What astounding discovery was made by the Buchners?

Question 24

Fructose can enter glycolysis at two distinct points, depending on the tissue. How is fructose metabolized in adipose tissue?

A) Fructose is cleaved to two molecules of GAP.
B) Fructose is converted to fructose-1-phosphate.
C) Fructose is converted to fructose-6-phosphate.
D) Fructose is cleaved to GAP and DHAP.
E) Fructose is converted to glucose, which enters the pathway.

Question 25

What reaction is catalyzed by aldolase?

A) isomerization of DHAP to GAP
B) hydrolysis of either GAP or DHAP
C) reversible cleavage of F-1,6-BP to DHAP and GAP
D) cleavage of DHAP to GAP
E) irreversible aldol condensation of DHAP and GAP

Question 26

How are the glycolytic enzymes regulated?

A) transcriptional control
B) reversible phosphorylation
C) allosteric control
D) All of the answers are correct.
E) reversible phosphorylation and allosteric control

Question 27

What is the function of a thioester intermediate such as the one formed from GAP?

A) It speeds up the actual reaction so that more product can be made.
B) The thioester shifts the equilibrium of the first stage of the reaction.
C) The thioester allows the two-step reaction to be coupled so the second reaction, the energetically unfavorable phosphorylation, can proceed.
D) The thioester intermediate induces a conformational change that alters the enzyme specificity.
E) The thioester prevents the formation of metabolically unfavorable side products.

Question 28

What two 3-carbon molecules are generated by the cleavage of fructose-1,6-bisphosphate?

A) glyceraldehyde-3-phosphate and 3-phosphoglycerate
B) glyceraldehyde-3-phosphate and dihydroxyacetone phosphate
C) pyruvate and phosphoenolpyruvate
D) enolase and 2-phosphoglycerate
E) glyceraldehyde-3-phosphate and pyruvate

Question 29

Why do muscles need to generate ATP under aerobic and anaerobic conditions?

Question 30

Which of the following are reasons that glucose is a common metabolic fuel used by living organisms?

A) In its stable ring structure, glucose is unlikely to nonezymatically glycosylate proteins.
B) It is one of the fuels formed under prebiotic conditions, thus available for primitive biochemical systems.
C) It is the only sugar used by the brain and kidney as a fuel source.
D) It is a ketose and thus a nonreducing sugar.
E) Both A and B are correct.

Question 31

What is the purpose of phosphorylating glucose in the cytosol?

A) to trap glucose in the cell
B) to destabilize glucose and facilitate the next series of metabolic steps
C) to convert it to a more soluble form
D) to slow the transport of glucose into the cell
E) Both A and B are correct.

Question 32

What two isomerization reactions occur in glycolysis? Why are these steps necessary?

Question 33

Both hexokinase and glucokinase phosphorylate glucose. The function of glucokinase is to phosphorylate glucose in liver cells as a means to regulate blood-sugar levels. Would you expect its K_M to be higher or lower than hexokinase? Explain your answer.

Question 34

What is the additional metabolite that is required for the conversion of 3-phosphoglycerate to 2-phosphoglycerate?

A) 1-phosphoglycerate
B) diacylglycerol
C) NADH
D) 2,3-bisphosphoglycerate
E) 1,3-bisphosphoglycerate

Question 35

At equilibrium, there is far more DHAP than GAP. Yet the conversion of DHAP by triose phosphate isomerase proceeds readily. Why?

Question 36

How many high-energy phosphate bonds are expended in gluconeogenesis?

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

Question 37

Two primary raw materials for gluconeogenesis in the human liver are

A) galactose and sucrose.
B) acetate and oxaloacetate.
C) lactate and alanine.
D) fructose and alanine.
E) lactose and lactate.

Question 38

What is substrate level phosphorylation?

A) phosphorylation of AMP by ATP
B) ATP synthesis when the phosphate donor is a substrate with high phosphoryl transfer potential
C) phosphorylation of glycolytic intermediates
D) phosphorylation of ATP coupled to an ion gradient
E) ATP and AMP synthesis from two molecules of ADP

Question 39

What are the primary metabolic fates of pyruvate?

A) ethanol
B) lactate
C) acetyl CoA
D) All of the answers are correct.
E) ethanol and lactate

Question 40

Lactose intolerance is caused by a deficiency of

A) lactase.
B) elastase.
C) lactose.
D) sucrase.
E) None of the answers is correct.

Question 41

How is glycolysis maintained under anaerobic conditions?

Question 42

How are gluconeogenesis and glycolysis regulated reciprocally?

Question 43

What two functions are attributed to substrate cycles?

Question 44

How does citrate influence glycolysis?

Question 45

Give the reactions by which glycerol (from fats) can be metabolized into pyruvate or synthesized into glucose.

Question 46

Why is it more sensible for phosphofructokinase to be an important control step, rather than hexokinase?

Question 47

During exercise, how is glycolysis regulated by feedforward stimulation?

Question 48

Which metabolic steps differ between glycolysis and gluconeogenesis?

Question 49

Describe the two isoforms of lactate dehydrogenase.

Question 50

Describe the biochemical explanation for galactosemia.

Question 51

How is the conversion of phosphoenolpyruvate to pyruvate accompanied by ATP formation?