Glycolysis

Question 1

the first reaction of glycolysis is? It is catalyzed by?

Answer 1

turning glucose into glucose-6-phosphate, by hexokinase

Question 2

the function of hexokinase is? It can act on? Its substitute in the liver is?

Answer 2

transfers phosphoryl groups between ATP and metabolites. Mannose, fructose, glucose. Glucokinase

Question 3

the second reaction of glycolysis is? It is catalyzed by?

Answer 3

glucose-6-phoshate into fructose-6-phosphate, by phosphoglucose isomerase. it is an isomerization of an aldose to a ketone

Question 4

what is the rxn mechanism of phosphoglucose isomerase?

Answer 4

substrate binding, an acid catalyzes the ring opening, a base takes the proton from C2 to form a CIS-ENEDIOLSTE-INTERMEDIATE, the proton is placed on C1, ring closure

Question 5

the third reaction of glycolysis is? It is catalyzed by?

Answer 5

fructose-6-phosphate is turned into fructose-1,6-biphosphate, by phosphofructokinase.

Question 6

the fourth reaction of glycolysis is? It is catalyzed by?

Answer 6

cleavage of fructose-1,6-biphosphate into 2 trioses named glyceraldehyde-3-phosphate and dihydroxyacetone phosphate, by aldolase

Question 7

there are 2 classes of aldolases explain the first of them

Answer 7

class 1: substrate binding, FBP’s carbonyl grp acts on E-amino grp of Lys to make iminium cation which is a protonated Schiff base, C3-O4 bond cleavage casing enamine formation and GAP release, protonation of enamine into iminium cation, hydrolysis of iminium cation to release DHAP

Question 8

there are 2 classes of aldolases explain the second one of them

Answer 8

they dont form a Schiff base, a divalent cation polarizes the carbonyl O of the substrate to stabilize the eno-late intermediate

Question 9

the fifth reaction of glycolysis is? It is catalyzed by?

Answer 9

interconversion of GAP and DHAP, by triose phosphate isomerase (TIM)

Question 10

the sixth reaction of glycolysis is? It is catalyzed by?

Answer 10

the oxidation phosphorylation of GAP, by NAD+ and P1, by GAP dehydrogenase

Question 11

what is the mechanism of GAPDH?

Answer 11

GAP bind to an enzyme, the sulfhydryl grp attacks to form thiomiacetal, this ungergoed oxidation into acyl thioester, a molecule of NAD+ replaces NADH, the intermediate undergoes nucleophiic attack by P1 to regenerate the free enzyme and form 1,3- BPG

Question 12

the seventh reaction of glycolysis is? It is catalyzed by?

Answer 12

formation of ATP and 3-phosphoglycerate, by phosphoglycerate kinase

Question 13

the eight reaction of glycolysis is? It is catalyzed by?

Answer 13

3-phosphoglycerate is converted into 2-phosphoglycerate, by phosphoglycerate mutase (transfer of a functional grp from one position to another

Question 14

the mechanism of a mutase is?

Answer 14

formation of an enzyme-substrate complex, transfer of an enzyme bound P group to a substrate, rephosphorylation of enzyme, release of porduct

Question 15

the ninth reaction of glycolysis is? It is catalyzed by?

Answer 15

2-phosphoglycerate turns into phosphoenolpyruvate, by enolase

Question 16

the tenth reaction of glycolysis is? It is catalyzed by?

Answer 16

coupling of free energy of PEP hydrolysis to synthesize ATP to form pyruvate, by pyruvate enzyme

Question 17

mechanism of pyruvate kinase is?

Answer 17

beta- phosphoryl O of ADP attacks the PEP P atom and form ATP , enol pyruvate converts into pyruvate. this is an enol-keto tautomerization

Question 18

glycolysis can be divided into 2 stages

Answer 18

1- consumption of 2ATP molecules

2- production of 4 ATP molecules (GAP-Pyruvate)

Question 19

the rate limiting enzyme is

Answer 19

PFK