Glycolysis and Glycogen

Question 1

Hexokinase

Answer 1

• Phosphorylates Glu to give G-6-P

- Traps the glucose in the cell because there are no G-6-P transporters

Question 2

Glucokinase

Answer 2

• Less aggressive hexokinase
• Transforms Glu to G-6-P
• Affinity 500 fold weaker than Hexokinase

Question 3

Phosphoglucose isomerase (PGI)

Answer 3

• Isomerizes an aldose to a ketose

- G6P to F6P

Question 4

Phosphofructokinase (PFK)

Answer 4

• Transfers phosphoryl group
• F6P to F-1,6-BP
• Key in regulation of glycolysis

Question 5

Aldolase

Answer 5

-Cleaves FBP into two trioses: DHAP and GAP

Question 6

Triose P Isomerase

Answer 6

-Interconverts a ketose (DHAP) to an aldose (GAP) through an Enediol intermediate

Question 7

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH)

Answer 7

-Oxidizes and phosphorylates GAP to 1,3-BPG

Question 8

Phosphoglycerate kinase (PGK)

Answer 8

• Converts 1,3-BPG to 3PG
• Yields 2 ATP
• Substrate level phosphorylation

Question 9

Phosphoglycerate mutase

Answer 9

• Moves the phosphoryl of 3PG to give 2PG

- Phosphohistidyl intermediate involved

Question 10

Enolase

Answer 10

• Dehydration

- Coverts 2PG to PEP

Question 11

Pyruvate kinase

Answer 11

• Coverts PEP to Pyruvate
• Produces ATP
• Substrate level phosphorylation

Question 12

Lactate dehydrogenase

Answer 12

• Converts pyruvate to lactate using NADH

- Reversible

Question 13

Conversion of Fructose into an glycolytic intermediate

Answer 13

• Hexokinase: converts Fructose to F6P

- In liver: Fructose converted to 2GAP using Fructokinase, F1P aldolase, glyceraldehyde kinase, and triose P isomerase

Question 14

F1P Aldolase Deficiency

Answer 14

• Liver damage and hypoglycemia

- F1P accumulates and gluconeogenesis decreases

Question 15

Conversion of Mannose to a gylcolytic intermediate

Answer 15

-Coverted to F6P using hexokinase and phosphomannose isomerase

Question 16

Conversion of Galactose to a glycolytic intermediate

Answer 16

-Converted to G6P using galactokinase, UMP transferase, epimerase, and phosphoglucomutase

Question 17

Galactokinase deficiency

Answer 17

• Galacitol formation
• Causes cataracts
• Solution: eliminate lactose from the diet
• Galactocemia

Question 18

UMP transferase deficiency

Answer 18

• Causes mental retardation and liver failure
• Solution: eliminate lactose from diet
• Galactocemia

Question 19

UDP-glucose pyrophosphorylase

Answer 19

-Converts G1P to UDP glucose in the synthesis of glycogen

Question 20

Glycogen synthase

Answer 20

-Converts UDP to glycogen along with branching enzyme

Question 21

Glycogen phosphorylase

Answer 21

-Breaks glycogen down to G1P along with a debranching enzyme

Question 22

Phosphoglucomutase

Answer 22

-Interconverts G1P to G6P

Question 23

Von Gierke Disease (Type 1 glycogen storage disease)

Answer 23

• Defective Glucose-6-phosphatase or transport system
• Affects liver and kidney
• Increased amount of glycogen with normal structure
• Massive enlargement of the liver, failure to thrive, severe hypoglycemia, ketosis, hyperuricemia, and hyperlipidemia

Question 24

McArdle Disease (Type 5 glycogen storage disease)

Answer 24

• Defective phosphorylase
• Affects the muscle
• Moderately increased amount of glycogen
• Limited ability to perform strenuous exercise because of painful muscle cramps

Question 25

Anderson Disease (Type 4 glycogen storage disease)

Answer 25

• Defecctive branching enzyme
• Affects the liver and spleen
• Normal amount of glycogen but with very long branches
• Progressive cirrhosis of the liver. Liver failure causes death before the age of 2.