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Origins > Origins 1: MCQ 2 > Flashcards

Origins 1: MCQ 2 Flashcards

1
Q

The oxidation of glucose under aerobic conditions is more efficient, in terms of ATP production, than under anaerobic conditions. Approximately how much faster would the rate of glucose utilization have to proceed in the absence of oxygen in order to produce an equivalent amount of ATP as that made under aerobic conditions.

A

About 15 times faster

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2
Q

The gluconeogenic pathway from pyruvate to glucose REQUIRES:

A

ATP and CO2
Cytosolic NADH
Both mitochondrial and cytosolic reactions

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3
Q

During active gluconeogenesis from pyruvate, CO2 is required for which reaction?

A

Pyruvate carboxylase

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4
Q

Which of the following statements is most likely to be FALSE?
A. Insulin can facilitate glucose uptake in muscle
B. GlucagoncanincreasethecytosolicconcentrationofcAMPinliver
C. Elevated levels of mitochondrial Ca2+ in muscle can inhibit the TCA cycle activity
D. A high NADH/NAD+ ratio in liver mitochondria can inhibit the TCA cycle activity
E. Strenuous muscle exercise with limited oxygen can elevate intracellular levels of lactate

A

C. Elevated levels of mitochondrial Ca2+ in muscle can inhibit the TCA cycle activity

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5
Q

Which statement about the pentose phosphate pathway is FALSE?
A. It can produce substrates for nucleotide synthesis from carbohydrates
B. It provides a means to produce NADPH for reductive biosynthesis
C. Glucose-6-phosphate is converted to ribose-5-phosphate
D. It provides a means to re-oxidize the cytosolic pool of NADH during active glycolysis
E. The pathway is active in the cytosol of liver

A

D. It provides a means to re-oxidize the cytosolic pool of NADH during active glycolysis

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6
Q

Which statement about cytochrome-c or its role in the electron transport chain is TRUE?
A. It is a small water-soluble protein attached to the outer surface of the inner mitochondrial
membrane.
B. It is the substrate for cytochrome-coxidase
C. It can accept electrons from Complex III
D.Its redox center contains a flavin mononucleotide
E. A, B, and C are correct

A

A, B, and C are correct

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7
Q

Which statement best describes the action of insulin in muscle?

A

It activates phosphoprotein phosphatase-1

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8
Q

Consider a preparation of respiring mitochondria that are provided an ample supply of succinate, ADP, and Pi. Oxygen is being consumed at a constant steady rate. Which statement best describes the results that will be observed upon addition of compound “X”, a known inhibitor of complex III?

A

ATP synthesis and oxygen consumption will cease

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9
Q

Which of the following reasons best explains why leucine and lycine are not substrates for gluconeogenesis in liver?

A

They are catabolized to acetyl-CoA

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10
Q

Caffeine inhibits cAMP phosphodiesterase. How does this affect the metabolic response to epinephrine?

A

It would prolong the effects of epinephrine through sustained activity of cAMP-dependent protein
kinases

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11
Q

A sample of liver glycogen is incubated with radio-labeled inorganic phosphate (32Pi), ATP, glycogen phosphorylase, and debranching enzyme. What are the products of this reaction? (Note: G1P = glucose-1-phosphate).

A

Approximately 10:1, 32P-labeled G1P: free glucose

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12
Q

In liver, all of the following may occur in response to increased levels of intracellular cAMP

A

1) Activation of phosphorylase kinase
2) Activation of glycogen phosphorylase
3) Activation of fluctose-2,6-bisphosphatase
4) Inhibition of phosphoprotein phosphatase-1

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13
Q

Which is the BEST reason why the glycerol phosphate shuttle will not operate, or will operate at a very slow rate, under anaerobic conditions?

A

Oxygen is required for the oxidation of the FADH2 cofactor for the mitochondrial glycerol
phosphate dehydrogenase enzyme

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14
Q

This is the substrate for complex IV in the electron transport chain

A

Cytochrome C

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15
Q

This is an inhibitor of Complex I (NADH dehydrogenase)

A

Rotenone

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16
Q

This is a small protein that is loosely attached to the outer surface of the inner mitochondrial membrane
and acts to accept electrons from Complex III during the electron transport process

A

Cytochrome C

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17
Q

This compound can transport protons across the inner mitochondrial membrane without passing through
the proton channel of ATP synthase

A

2,3-dinitrophenol

18
Q

This small molecule is trapped within the inner mitochondrial membrane, but it is mobile and can
transport electrons to Complex III from Complexes I and II

A

Ubiquinone

19
Q

The pentose phosphate pathway involves:

A

The oxidation of glucose-6-phosphate to ribose-5-phosphate with the production of 2 NADPH

20
Q

Which statement describes the toxic mechanism of cyanide?

A

It is an inhibitor of cytochrome coxidase (ComplexIV)

21
Q

Which statement about glycogen or its biosynthesis is FALSE?
A. It is stored as granuoles in the cytosol of muscle and liver cells
B. It has a highly branched structure and a molecular weight in the millions
C. It contains both α-1,4 and α-1,6 glycosidic-linked glucose monomers
D. A self glycosylating protein known as glucogenin provides a primer of glucose monomers to initiate
glycogen synthesis
E. It is synthesized in the mitochondria and then exported into the cytosol for storage

A

E. It is synthesized in the mitochondria and then exported into the cytosol for storage

22
Q

Which “chemical strategy” is a common feature in the first two reaction steps for the biosynthesis of glucose from pyruvate (starting with the pyruvate carboxylase reaction), and the biosynthesis of fatty acids from acetyl-CoA (starting with the acetyl-CoA carboxylase reaction)?

A

Consumption of ATP, and carboxylation followed by decarboxylation

23
Q 
Consider an isolated system of mitochondria that are oxidizing pyruvate at a steady state with consumption of oxygen and production of ATP and CO2. What will happen if 2,4-dinitrophenol (an uncoupler) is added to the preparation?
A. Oxygen consumption will increase
B. ATP production will decrease
C. Consumption of pyruvate will increase
D. CO2 production will increase
E. All of the above
A

E. All of the above

24
Q

What are the NET products when 1 mole of acetyl-CoA is oxidized via the TCA cycle?

A

1 GTP + 1 FADH2 + 3 NADH + 2 CO2

25
Q

Which statement about the first phase of glycolysis from glucose to the trioses (DHAP and GA3P) is TRUE?

A

ATP is consumed in this portion of the pathway

26
Q

Which reaction is catalyzed by serine hydroxymethyltransferase? (Note: THF = tetrahydrofolate)

A

Serine + THF → glycine + 5,10-CH2-THF

27
Q

Which represents a correct pathway for glycogen synthesis?

A

Glucose → G6P → G1P → UDP-glucose → glycogen

Note: G1P = glucose-1-phosphate; G6P = glucose-6-phosphate; R5P = ribose-5-phosphate; UDP = uridine diphosphate

28
Q

Elevated levels of blood insulin can lead to down-regulation of gene transcription for phosphoenolpyruvate carboxykinase (PEPCK) in liver. What is the metabolic significance of this?

A

It will inhibit gluconeogenesis

29
Q

Methotrexate is a cancer chemotherapy drug that acts to inhibit DNA synthesis in rapidly proliferating cells. What is the mechanism of action of methotrexate?

A

It is an inhibitor of dihydrofolate reductase and effectively lowers the amount of THF that is
available for the thymidylate synthase reaction

30
Q

All of the following will lead to glycogen degradation in liver EXCEPT:
A. Activation of phosphoprotein phosphatase-1 (PP-1)
B. The binding of epinephrine to its receptor at the cell surface
C. The binding of glucagons to its receptor at the cell surface
D. Activationofadenylatecyclase
E. An increase in calcium ion and 5’-AMP

A

Activation of phosphoprotein phosphatase-1 (PP-1)

31
Q 
All
A. Lactate
of the following will lead to glycogen degradation in liver EXCEPT:
of the following compounds can be used for glucose synthesis in liver EXCEPT:
B. Alanine
C. Acetyl-CoA
D. Malate
E. Glycerol
A

C. Acetyl-CoA

32
Q

Consider muscle during strenuous exercise. Glucose is being oxidized at a high rate but the supply of oxygen to the tissue is limited and cellular conditions become anaerobic. What would be the final product of glucose catabolism?

A

Lactate

33
Q

Which of the following mechanisms can inhibit the pyruvate dehydrogenase complex (PDH)?

A

A rise in the mitochondrial NADH:NAD+ ratio

34
Q

What is the NET yield when 3 moles of lactate are completely oxidized by action of lactate dehydrogenase, pyruvate dehydrogenase, and the TCA cycle?

A

9 CO2 + 15 NADH + 3 FADH2 + 3 GTP

35
Q

What is the NET yield of ATP and NADH for the conversion of 1 mole of glycerol to pyruvate?

A

1 ATP + 2 NADH

36
Q

What is the NET ATP produced or consumed when 1 mole of glucose is synthesized from glycerol via gluconeogenesis in liver?

A

3.0 ATP produced

37
Q

All of the following represent a means to generate the reduced form of the cofactor, NADH, in the cytosol EXCEPT:
A. Pyruvate → lactate via the cytosolic lactate dehydrogenase reaction
B. Malate → oxaloacetate → aspartate (inthecytosol)
C. Transport of NADH from the mitochondria to the cytosol via a NAD-linked transporter protein
D. Glyceraldehyde-3-phosphate → 1,3-bisphosphoglycerate via cytosolic glyceraldehydes-3-phosphate
degydrogenase
E. A and C

A

A and C

38
Q

This is a major regulatory enzyme in gluconeogenesis. Prolonged elevated levels of insulin can cause the down-regulation in gene transcription of this protein in the liver.

A

Phosphoenolpyruvatecarboxykinase

39
Q

How many moles of nucleotide triphosphates (ATP, GTP, etc) are needed to synthesize 10 moles of glucose from pyruvate via gluconeogenesis in the liver?

A

60

40
Q

Which enzyme enables the liver to export glucose into the blood?

A

Glucose-6-phosphate phosphatase

41
Q

High quantities of linolenic acid in the diet leads to adipose tissue triglycerides which contain a large amount of which fatty acid?

A

18:3

42
Q

Lack of insulin, as in uncontrolled diabetes, would have what effect on adipose tissue triglycerides?

A

Increased degradation

Origins (4 decks)

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