Glycolysis pathway

Question 1

glucose

Answer 1

glucose-6-phosphate

Question 2

SGLUT1

Answer 2

Expressed in intestinal mucosa, kidney tubules

Co-transport: 1 molecule of glucose or galactose with 2Na

Question 3

GLUT2

Answer 3

Expressed in: liver, pancreatic beta cells, small intestine, kidney.
Transports: glucose, galactose and fructose.
Low affinity-High capacity
Is the glucose ‘sensor’ in pancreatic beta cells.

Question 4

GLUT4

Answer 4

Expressed in: Skeletal and cardiac muscles, adipocytes
Insulin-responsive
Transports glucose
high affinity

Question 5

Hexokinase

Answer 5

Glucose+ATP –> Glucose-6-phosphate + ADP
∆G=-27KJ/mol
irreversible
Hexokinase I: km=0.03mM, most tissues, inhibited by G6P
Hexokinase II: km=0.3mM. In muscle, adipose tissue. Inhibited by G6P

In muscle: Fructose + ATP –> Fructose-6-phosphate + ADP –≥ glycolysis

Question 6

Glucokinase

Answer 6

Glucose+ATP–> ADP+ glucose-6phosphate
km=5mM (blood conc.). In liver and pancreas. Not inhibited by G6P!
Glucokinase regulatory protein: bound to glucokinase in the cell nucleus. It is released into the cytoplasm when high blood glucose to catalyze the reaction.

Question 7

Phosphofructokinase

Answer 7

fructose-6-phosphate + ATP (Mg++)–> fructose-1,6-bisphosphate+ ADP
∆G=-26 KJ/mol
commiting step to glucose metabolization
Inhibitors: ATP, citrate,phosphoenolyruvate
Activators (deinhibitor of ATP): ADP, AMP, cAMP, FBP, F2,6P, F6P, NH4+, Pi

Question 8

Adenylate kinase

Answer 8

2ADP ATP + AMP

Question 9

Fructokinase

Answer 9

Fructose + ATP –> Fructose-1-phosphate + ADP Fructose-1-phosphate (open chain)
- 1st reaction in fructose liver metabolism.

Question 10

Fructose-1-phosphate aldolase

Answer 10

Fructose-1-phosphate –> glyceraldehyde

• 2nd reaction in fructose liver metabolism
• type b in liver: uses F-1-P

Question 11

Glyceraldehyde kinase

Answer 11

Glyceraldehyde + ATP –> Glyceraldehyde-3phosphate + ADP –> Glycolysis

-3rd step in fructose liver metabolism

Question 12

Alcohol dehydrogenase

Answer 12

Glyceraldehyde + NADH –> Glycerol + NAD+

-4th step in fructose liver metabolism

Question 13

glycerol kinase

Answer 13

glycerol + ATP –> glycerol-3-phosphate + ADP

-5th step in fructose liver metabolism

Question 14

glycerol phosphate dehydrogenase

Answer 14

Glycerol-3-phosphate+ NAD –> dihydroxyacetone + NADH

-6th step in fructose liver metabolism

Question 15

triose phosphate isomerase

Answer 15

Dihydroxyacetone phosphate –> Glyceraldehyde-3-phosphate –> glycolysis.

7th and last step in fructose liver metabolism.

Question 16

Fructose intolerance

Answer 16

genetic
Lack of F-1-P aldolase
-Symptoms: liver damage (jaundice), diarrhea, vomiting
-Buildup of F-1-P –> results in reduced ATP + Pi (in order to make ATP)
-treatment: don’t eat fructose

Question 17

Galactokinase

Answer 17

Galactose + ATP –> Galactose-1-phosphate + ADP (irreversible)

1st step in galactose metabolism

Question 18

Galactose-1-phosphate uridylyl transferase

Answer 18

Galactose-1-phosphate + UDP-glucose –> UDP-galactose + Glucose-1-phosphate

2nd step in galactose metabolism

Question 19

UDP-galactose-4-epimerase

Answer 19

UDP-galactose –> UDP-glucose

-3rd step in galactose metabolism

Question 20

phosphoglucomutase

Answer 20

Glucose-1-phosphate glucose-6-phosphate –≥ glycolysis.

Question 21

Galactosemia, type 1

Answer 21

Uridylyl transferase deficiency

• Most common
• Symptoms: mental retardation, liver damage, cataract
• Treatment: removal of galactose and lactose from diet
• Worst type because of ATP + pi depletion

Question 22

Galactosemia, type 2

Answer 22

galactokinase deficiency

Question 23

Galactosemia, type 3

Answer 23

epimerase deficiency

Question 24

Galactose making

Answer 24

G1P + UtP –> UDP glucose + PPi

PPi (inorganic pyrophosphatase) –>2Pi coupled with UDP-glucose (UDP-galactose-4-epimerase) –> UDP galactose

-UDP-galactose + Glucose (lactose synthase) –> Lactose