2.1 Fructose metabolism

Question 0

What are the two monosaccharides that make up Sucrose

Answer 0

Glucose and Fructose

Question 1

Key sources of fructose in diet

Answer 1

Fructose
High Fructose Corn Syrup
Sucrose

Question 2

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

Answer 2

Sucrose is a disaccharide of Glucose and Fructose

HFCS is a mixture of monosaccharides of Glucose and Fructose

Question 3

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

Answer 3

Through GLUT 5

Facilitated Transport

Question 4

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

Answer 4

GLUT 5 or GLUT 2 (mainly GLUT 2)

Facilitated Transport

Question 5

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

Answer 5

Fructose –> Fructose 6-phosphate

Question 6

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

Answer 6

Hexokinase

Question 7

How does Fructose enter glycolysis in the liver

Answer 7

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

Question 8

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

Answer 8

Fructokinase

Question 9

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

Answer 9

Aldolase B (Fructose 1-phosphate aldolase)

Question 10

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

Answer 10

It bypasses PFK1

Question 11

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

Answer 11

Increased lipogenesis and Increased appetite

Question 12

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

Answer 12

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

Question 13

What are the two major genetic disorders of fructose metabolism

Answer 13

Enzyme deficiency with Fructokinase

Enzyme deficiency with Aldolase B

Question 14

Which genetic disorder of fructose metabolism is severe

Answer 14

Enzyme deficiency with Aldolase B or Hereditary fructose intolerance

Question 15

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

Answer 15

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

Question 16

What is the purpose of converting glucose to sorbitol?

Answer 16

To trap glucose in the cell without expending ATP.

Question 17

What enzyme catalyzes the reaction of Glucose to Sorbitol?

Answer 17

Aldose Reductase

Question 18

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

Answer 18

NADPH

Question 19

When is there a buildup of Sorbitol?

Answer 19

During hyperglycemia

Question 20

In what cells does Sorbitol build up and why?

Answer 20

Lens, Kidney and Nerve

Sorbitol cannot be converted to Fructose in these cells

Question 21

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

Answer 21

Sorbitol Dehydrogenase

Question 22

How does Mannose enter glycolysis?

Answer 22

By being converted to Fructose 6-phosphate

Question 23

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

Answer 23

Hexokinase

Question 24

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

Answer 24

Phosphomannose isomerase

Question 25

How does Galactose enter glycolysis?

Answer 25

Glucose 6-phosphate

Question 26

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

Answer 26

* 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)

Question 27

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

Answer 27

Galactokinase

Question 28

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

Answer 28

Galactose 1-phosphate uridylyl transferase

Question 29

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

Answer 29

UDP-Galactose-4-epimerase

Question 30

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

Answer 30

Phosphoglucomutase

Question 31

Name the seven tissues that has the Pentose Phosphate Pathway

Answer 31

``` Mammary Gland Adipose tissue Adrenal Cortex Liver Testes Ovaries Red Blood Cells ```

Question 32

What are the two major products of the Pentose Phosphate Pathway

Answer 32

NADPH and Ribose 5-Phosphate

Question 33

Briefly outline the Oxidative pathway of PPP

Answer 33

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

Question 34

Enzyme for conversion of 6 Phosphogluconolactone from G6P in oxidative PPP

Answer 34

GLucose 6-phosphate dehydrogenase

Question 35

Enzyme that catalyzes reaction of 6 Phosphogluconolactone to 6 Phosphogluconate

Answer 35

Lactonase

Question 36

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

Answer 36

6 Phosphogluconate Dehydrogenase

Question 37

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

Answer 37

Phosphopentose Isomerase

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

What does Glutathione do?

Answer 40

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

Question 41

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

Answer 41

Glutathione Reductase | NADPH

Question 42

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

Answer 42

Glutathione Peroxidase

Question 43

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

Answer 43

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