Glycolysis

Question 1

Transport of glucose into cells

Answer 1

• across membrane on transport protein
• insulin stimulates glucose transport into muscle and adipose cells by relocation of the 4 transport proteins ti the cell membrane (GLUT1,GLUT2,GLUT3)

Question 2

Steps of glycolysis

Answer 2

glucose- glucose6P- fructose6P- fructose 1,6bisP- dihydroxyacetone phosphate/glyceraldehyde 3P- 1,3bisphosphoglycerate- 3-phosphoglycerate- 2-phosphoglycerate- phosphoenolpyruvate- pyruvate

Question 3

glucose -> glucose 6 P

Answer 3

-IRREVERSIBLE
-enzymes: HEXOKINASE(low Km for glucose, working at low Vmax, inhibited by its product, requires Mg2+ for its activity),
GLUCOKINASE(in liver, high Km for glucose, induced by high insulin levels, not inhibited by its product, inhibited by fructose-6-phosphate, regulated by glucokinase regulatory protein GKRP)

Question 4

Glucose 6P-> Fructose 6P

Answer 4

• reversible
• aldose isomerized to a ketose
• enzyme: PHOSPHOGLUCOSE ISOMERASE

Question 5

Fructose 6P-> Fructose 1,6bisP

Answer 5

• IRREVERSIBLE
• enzyme: PHOSPHOFRUCTOKINASE 1 (inhibited by: high ATP and high PEP, activated by: high ADP/AMP and high F-2,3-BP)
• first committed step

Question 6

Fructose 1,6bisP-> Dihydroxyacetone phosphate/Glyceraldehyde 3 phosphate

Answer 6

-reversible
-fructose molecule cleaved into 2 three carbon molecules
-enzymes: ALDOLASE (cleaves fructose bw C3 and C4, aldolase A in muscle, B in liver)
TRIOSE PHOSPHATE ISOMERASE(isomerizes DHAP into glyceraldehyde 3P)

Question 7

Glyceraldehyde 3P-> 1,3 bisphosphoglycerate

Answer 7

• reversible
• oxidized by NAD+ and reacts with Pi
• enzyme: GLYCERALDEHYDE 3 PHOSPHATE DEHYDROGENASE (NAD-dependent)

Question 8

1,3 bisphosphoglycerate-> 3 phosphoglycerate

Answer 8

• reversible
• molecule reacts with ADP->ATP
• enzyme: PHOSPHOGLYCERATE KINASE

Question 9

3 phosphoglycerate-> 2 phosphoglycerate

Answer 9

• reversible
• enzyme: PHOSPHOGLYCEROMUTASE
• requires Mg2+

Question 10

2 phosphoglycerate-> Phosphoenolpyruvate

Answer 10

• reversible
• dehydrogenation
• enzyme: ENOLASE (requires Mg2+ or Mn2+, inhibited by fluoride)

Question 11

Phosphoenolpyruvate-> Pyruvate

Answer 11

• IRREVERSIBLE

- enzyme: PYRUVATE KINASE (requires Mg2+ or Mn2+ and K+,inhibited by:ATP,Acetyl-CoA, Alanine, activated by:F-1,6-BP)

Question 12

Glycolysis 2 phases

Answer 12

1. Investment phase (first 5 rxns, invest 2ATP)

2. Pay.off phase (last 5rxns, produce 4ATP)

Question 13

Fate of pyruvate

Answer 13

• Conversion to lactate: by lactate DH
• Conversion to Acetyl-CoA
• Conversion to oxaloacetate: by pyruvate carboxylase
• Conversion to alanine: by alanine aminotransferase

Question 14

Shuttle systems

Answer 14

• Glycerol phosphate shuttle

- Malate-aspartate shuttle