2017 Biochemistry - Glycolysis

Question 1

Reactants and Products of Hexokinase/Glucokinase - Step 1?

Answer 1

Glucose + ATP -> G6P

Question 2

Reactants and Products of Phosphofructokinase - Step 3?

Answer 2

Fructose-6-P + ATP -> Fructose-1,6-bisphosphate

Question 3

Reactants and Products of Pyruvate Kinase - Step 9?

Answer 3

Phosphoenolpyruvate + ADP -> Pyruvate + ATP

Question 4

Which steps of Glycolysis produce ATP?

Answer 4

Step 6 & 9

Phosphoglycerate kinase and Pyruvate Kinase

Question 5

Which steps of Glycolysis use ATP?

Answer 5

Step 1 & 3

Hexokinase/Glucokinase and Phosphofructokinase

Question 6

What are the 3 enzymes responsible for the irreversible steps of Glycolysis?

Answer 6

Hexokinase/Glucokinase - step 1
Phosphofructokinase - step 3
Pyruvate kinase - step 9 & final step

Question 7

Differences/Similarities between Hexokinase and Glucokinase?

Answer 7

Glucokinase - present only in liver, kidney and B cells, low affinity = function is to remove glucose from blood following a meal, not inhibited by G6P.

Hexokinase - present in all tissues, very high affinity = saturated under normal condition and acts as a constant rate, Inhibited by G6P

Question 8

Aerobic Glycolysis; products, ATP produced, shuttle system

Answer 8

• Pyruvate is converted to acetyl-CoA in mitocondria for TCA cycle
• Oxidation of ACoA will lead to 36 ATP produced
• Under aerobic conditions NADH which is produced may be re-oxidized by mitochondria through a shuttle system.

Question 9

Primary purpose of Anaerobic Glycolysis?

Answer 9

To regenerate NAD+ using the G3P shuttle.
This allows NADH equivalents to get out of the mitochondria.
Pyruvate is reduced to Lactate

Question 10

What are the inhibitors of Hexokinase?

Answer 10

Glu-6-P, ATP

Question 11

What are the Activators/Inhibitors of PFK-1?

Answer 11

Activators: F-2,6-bP, AMP
Inhibitors: Citrate, ATP

Question 12

What are the Activators/Inhibitors of Pyruvate Kinase?

Answer 12

Activators: F-2,6-bP, AMP
Inhibitors: Acetyl-CoA, ATP

Question 13

What enzyme is used in Erythrocytes to bypass the “normal” route from Glyceraldehyde-3-p –> 3-Phosphoglycerate, which product is made in place of 1,3-bPG and what is it’s importance?

Answer 13

Biophosphglycerate mutase

2,3-bPG is made in RBCs which binds to Hb and decreases it’s affinity for O2, thus freeing O2 for use in tissue.

Question 14

What are the 3 enzymes important to fructose metabolism?

Answer 14

Fructokinase: Fructose + ATP -> Fructose-1-p
Adolase B: Fructose-1-p Glyceraldehyde + Dihydroxyacetone phosphate
Triose Kinase: Glyceraldehyde + ATP -> Glyceraldehyde-3-phos.

Question 15

Which enzyme of fructose metabolism is blocked in Essential Fructosuria?

Answer 15

Fructokinase

Question 16

Which enzyme of fructose metabolism is blocked in Hereditary Fructose Intolerance?

Answer 16

Aldolase B

Question 17

Galactose metabolism: important enzymes and resultant product

Answer 17

1. Galactokinase
2. UPD-Glc:Gal-1-P uridylyltransferase
3. Phosphoglucomutase

Results in Glucose-6-P production

Question 18

Which enzyme is lacking/faulty in Galactosemia?

Answer 18

Galactose-1-phosphate uridyltransferase

Question 19

Mannose metabolism: important enzymes and resultant products

Answer 19

Mannose Kinase (liver) converts mannose to Mannose-6-P
Phosphomannose isomerase catalyzes Mannose-6-P to F-6-P

Question 20

One molecule of glucose converts to how many molecules of pyruvate through Glycolysis?

Answer 20

1 molecule glucose = 2 molecules of pyruvate