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Metabolism > 2.1 Fructose metabolism > Flashcards

2.1 Fructose metabolism Flashcards

0
Q

What are the two monosaccharides that make up Sucrose

A

Glucose and Fructose

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1
Q

Key sources of fructose in diet

A

Fructose
High Fructose Corn Syrup
Sucrose

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2
Q

What is the key difference between High Fructose Corn Syrup and Sucrose

A

Sucrose is a disaccharide of Glucose and Fructose

HFCS is a mixture of monosaccharides of Glucose and Fructose

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3
Q

Fructose absorption into the intestinal cells occurs how and through what type of transport?

A

Through GLUT 5

Facilitated Transport

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4
Q

Fructose absorption into the bloodstream from the intestinal cells occurs how and through what type of transport?

A

GLUT 5 or GLUT 2 (mainly GLUT 2)

Facilitated Transport

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5
Q

In the muscle, how in what structure does fructose enter glycolysis

A

Fructose –> Fructose 6-phosphate

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6
Q

What enzyme catalyzes the reaction of Fructose to Fructose 6-phosphate in the muscle?

A

Hexokinase

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7
Q

How does Fructose enter glycolysis in the liver

A

Fructose –> Fructose 1-phosphate –> Glyceraldehyde and Dihydroxyacetone phosphate –> Glyceraldehyde 3-phosphate

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8
Q

What enzyme catalyzes reaction of fructose to fructose 1-phosphate in the liver

A

Fructokinase

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9
Q

What enzyme catalyzes Fructose 1-phosphate to Glyceraldehyde and Dihydroxyacetone phosphate

A

Aldolase B (Fructose 1-phosphate aldolase)

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10
Q

What crucial step of normal glycolysis does Fructose skip as it enters glycolysis in the liver?

A

It bypasses PFK1

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11
Q

What is the result of Fructose bypassing PFK1 in the liver?

A

Increased lipogenesis and Increased appetite

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12
Q

Excessive dietary intake of fructose may lead to decrease in what?

A

available phosphate which means that it is insufficient to meet demands of ATP regeneration

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13
Q

What are the two major genetic disorders of fructose metabolism

A

Enzyme deficiency with Fructokinase

Enzyme deficiency with Aldolase B

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14
Q

Which genetic disorder of fructose metabolism is severe

A

Enzyme deficiency with Aldolase B or Hereditary fructose intolerance

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15
Q

What happens when there is an enzyme deficiency with fructokinase in the liver?

A

Fructose cannot be phosphorylated to fructose 1-phosphate and cannot be trapped in the cell. This could lead to Essential Fructosuria

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16
Q

What is the purpose of converting glucose to sorbitol?

A

To trap glucose in the cell without expending ATP.

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17
Q

What enzyme catalyzes the reaction of Glucose to Sorbitol?

A

Aldose Reductase

18
Q

What coenzyme is used in the reaction of Glucose to Sorbitol?

A

NADPH

19
Q

When is there a buildup of Sorbitol?

A

During hyperglycemia

20
Q

In what cells does Sorbitol build up and why?

A

Lens, Kidney and Nerve

Sorbitol cannot be converted to Fructose in these cells

21
Q

Sorbitol is converted to Fructose by what enzyme in the Liver?

A

Sorbitol Dehydrogenase

22
Q

How does Mannose enter glycolysis?

A

By being converted to Fructose 6-phosphate

23
Q

Reaction of Mannose to Mannose 6-phosphate is catalyzed by what enzyme?

A

Hexokinase

24
Q

Mannose 6-phosphate to Fructose 6-phosphate reaction is catalyzed by what enzyme?

A

Phosphomannose isomerase

25
Q

How does Galactose enter glycolysis?

A

Glucose 6-phosphate

26
Q

Briefly outline the pathway of Galactose being converted to Glucose 6-phosphate

A
  • Galactose –> Galactose 1-phosphate
  • Galactose 1-phosphate + UDP-Glucose –> UDP-Gal + Glu 1-Phosphate
  • Glucose 1-phosphate –> Glucose 6-phosphate
  • *UDP-galactose –> UDP-glucose (to be used to produce glu-1-P)
27
Q

What enzyme catalyzes the reaction of Galactose –> Galactose 1-phosphate

A

Galactokinase

28
Q

What enzyme catalyzes the placement of uridine phosphate on Galactose 1-phosphate and the production of Glucose-1-phosphate

A

Galactose 1-phosphate uridylyl transferase

29
Q

What enzyme catalyzes reaction of UDP-galactose to UDP-glucose?

A

UDP-Galactose-4-epimerase

30
Q

What enzyme catalyzes reaction of Glucose 1-phosphate to Glucose 6-phosphate in the galactose metabolism

A

Phosphoglucomutase

31
Q

Name the seven tissues that has the Pentose Phosphate Pathway

A 
Mammary Gland
Adipose tissue
Adrenal Cortex
Liver
Testes
Ovaries
Red Blood Cells
32
Q

What are the two major products of the Pentose Phosphate Pathway

A

NADPH and Ribose 5-Phosphate

33
Q

Briefly outline the Oxidative pathway of PPP

A

Glucose 6-Phosphate –> 6 Phosphogluconolactone
6 Phosphogluconolactone –> 6 Phosphogluconate
6 Phosphogluconate –> Ribulose 5-Phosphate

34
Q

Enzyme for conversion of 6 Phosphogluconolactone from G6P in oxidative PPP

A

GLucose 6-phosphate dehydrogenase

35
Q

Enzyme that catalyzes reaction of 6 Phosphogluconolactone to 6 Phosphogluconate

A

Lactonase

36
Q

6 Phosphogluconate to Ribulose 5 Phosphate is catalyzed by what enzyme?

A

6 Phosphogluconate Dehydrogenase

37
Q

What enzyme catalyzes reaction of Ribulose 5 phosphate to Ribose 5-Phosphate

A

Phosphopentose Isomerase

38
Q

When Ribose 5-Phosphate is needed more than NADPH in Non-Oxidative pathway, outline pathway

A

(2) Fructose 6-phosphate and (1) Glyceraldehyde 3-Phosphate –> (3) Ribose 5-phosphate

39
Q

Outline the pathway when more NADPH is needed than Ribose 5-phosphate

A

(3)Ribose 5-Phosphate is recycled to form (2)Fructose 6-phosphate and (1)Glyceraldehyde 3-Phosphate

40
Q

What does Glutathione do?

A

It reduces H202 to make 2 H20 and becomes oxidized in the meantine

41
Q

When Glutathione is oxidized and needs to be become reduced, what enzyme and coenzyme help accomplish this.

A

Glutathione Reductase

NADPH

42
Q

What enzyme is involved in oxidizing Glutathione when it gives up its 2 H ions to H2O2?

A

Glutathione Peroxidase

43
Q

What is the effect of a Glucose 6 phosphate dehydrogenase deficiency?

A

Disrupts the reformation of NADPH that is used to reduce Glutathione. The ability to detoxify oxidizing agents is disrupted.

Metabolism (31 decks)

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