MTC Week 6

Question 1

what are the net overall products of glycolysis?

Answer 1

2x pyruvate

2x ATP

2x NADH

Question 2

in which state is glycolysis a major source of energy?

Answer 2

fed-state

Question 3

where in cells do these reactions occur?

Answer 3

cytosol

Question 4

how is energy involved differently in steps 1-5 of glycolysis vs 6-10?

Answer 4

Steps 1-5: Energy-investing reactions

Steps 6-10: Energy-harvesting reactions

Question 5

which steps are irreversible?

Answer 5

1, 3, 10

Question 6

starting from the molecule glucose, state the molecule formed, the action and the enzyme used in step 1 of glycolysis

Answer 6

starts from glucose

Reaction: ATP to ADP + a phosphate

Enzyme: Hexokinase/glucokinase in the liver

Molecule formed: glucose 6 phosphate

Question 7

state the molecule formed, the action and the enzyme used in step 2 of glycolysis

Answer 7

Carbonyl group from C1 to C2

Enzyme: hexose isomerase/ phosphohexose isomerase

Molecule: fructose 6 P

Question 8

state the molecule formed, the action and the enzyme used in step 3 of glycolysis

Answer 8

Reaction: ATP to ADP + a p

Enzyme: phosphofructokinase

Molecule: fructose 1,6-bisphophate

Question 9

state the molecule formed, the action and the enzyme used in step 4 of glycolysis

Answer 9

Forms Molecules 2 three carbon sugar (triose) phosphates

• Dihydroxy-acetone phosphate (DHAP)
• Glyceraldehyde 3-phosphate (G3P)

Enzyme: aldolase (cleaves)

Question 10

state the molecule formed, the action and the enzyme used in step 5 of glycolysis

Answer 10

Dihydroxy-acetone phosphate is converted to Glyceraldehyde 3-phosphate

• Enzyme: Triose phosphate isomerase

Question 11

state the molecule formed, the action and the enzyme used in step 6 of glycolysis

Answer 11

Reaction: NAD to NADH2

Free inorganic phosphate (Pi) onto C1

Enzyme: glyceraldehyde 2-phosphate dehydrogenase

Molecule: 1,3-bisphosphoglycerate (1-3-PGA) x2 molecules

Question 12

state the molecule formed, the action and the enzyme used in step 7 of glycolysis

Answer 12

• Reaction: ADP to ATP
• Molecule: 3-phosphoglycerate (3PG)
• Enzyme: 3-phosphoglycerate kinase

Question 13

state the molecule formed, the action and the enzyme used in step 8 of glycolysis

Answer 13

• Phosphate group of 3PG is moved from C2 to C3
• Molecule: 2-phosphoglycerate
• Enzyme: phosphoglycerate mutase

Question 14

state the molecule formed, the action and the enzyme used in step 9 of glycolysis

Answer 14

• Removes water from 2PG
• Molecule: phosphoenolpyruvate (PEP)
• Enzyme: enolase

Question 15

state the molecule formed, the action and the enzyme used in step 10 of glycolysis

Answer 15

• Molecule: pyruvate
• ADP to ATP
• Enzyme: pyruvate kinase

Question 16

how is glycolysis regulated with glucokinase and hexose

Answer 16

(Step 1)

Glucokinase (liver): is induced by insulin, occurs as glucose levels are high to store glucose as glycogen

Hexose: allosteric inhibition by G6P

Question 17

how is glycolysis regulated with PFK1

Answer 17

(step 3)

allosteric regulation of PFK1

Question 18

what are the 3 allosteric activators of PFK1

Answer 18

F2,6BP

ADP

AMP

Question 19

what are the 2 allosteric inhibitors of PKF1

Answer 19

ATP (binds PKF1 and decreases its affinity for F6P)

Citrate

Question 20

what are the 2 allosteric regulators of PKF1

Answer 20

PFK2 (catalyses phosphorylation of F6P to F2,6BP)

F2,6BP (stimulates PKF1)

Question 21

how does insulin and glucagon affect PFK2

Answer 21

Insulin regulation: stimulates PFK2 activity → increases F2,6BP → activates PFK1

Glucagon regulation: stimulates F2,6Bpase activity → decrease F2,6BP → inhibits PFK1

Question 22

how is glycolysis regulated with PK

Answer 22

(Step 10)

allosteric regulation by PK activity

Question 23

what are the 2 allosteric activators of PK

Answer 23

F1,6BP (upregulates PK - feed forward stimulation)

ADP

Question 24

what are the 2 allosteric inhibitors of PK

Answer 24

ATP

Alanine

Question 25

how does insulin and glucagon regulate PK

Answer 25

insulin stimulates dephosphorylation of PK (active form) glucagon stimulates phosphorylation of PK (inactive form)

Question 26

where is fructose metabolized

Answer 26

liver

Question 27

describe the steps of fructose metabolism

Answer 27

Fructokinase (FK) form Fructose-1-phosphate (F1P) F1P is cleaved by Aldolase B (ALD B) to DHAP and glyceraldehyde (GA). DHAP goes into glycolysis GA is phosphorylated by Triose kinase to form glyceraldeyhde-3-phosphate (G3P), & goes into glycolysis. TPI: Triosephosphate Isomerase

Question 28

what is the function of lactase and where is it found

Answer 28

to digest milk located in the microvilli cells of the small intestine

Question 29

what are the 3 enzymes required to breakdown galactose

Answer 29

Galactokinase (GALK): galactose to galactose-1-phosphate. Galactose-1-phosphate uridyltransferase: Transfer of UDP from UDP-glucose (glycogenesis). UDP-galactose-4’-epimerase (GALE): Reversible epimerization of UDP-glucose to UDP-galactose