Biochemistry

Front 1

Which enzyme catalyzes the first reaction in glycolysis?

Back 1

hexokinase

Front 2

What gets turned into what in the first reaction in glycolysis?

Back 2

glucose gets turned into glucose-6-phosphate (G6P)

Front 3

Kinase

Back 3

is an enzyme that transfers phosphoryl groups between ATP and a metabolite

(the metabolite that serves as the phosphoryl group acceptor is indicated in the prefix of the kinase name

Front 4

Is hexokinase a specific enzyme?

Back 4

No, it is a nonspecific one because it will also catalyze the phosphorylation of hexoses like D-glucose, D-manose, and D-fructose

Front 5

Name one isozyme from hexokinase?

Back 5

glucokinase which is found in the liver

Front 6

What is the second substrate for hexokinase?

Back 6

Mg2+-ATP complex

Front 7

Is uncomplexed ATP a potent competitive inhibitor for of hexokinase?

Back 7

Yes, because without the Mg2+ shielding the negative charges of the ATP's alpha and beta or alpha and gamma-phosphate oxygen atoms, the nucleophilic attack of the C6-OH group of glucose is more difficult

Front 8

Does glucose induce a large conformational change in hexokinase?

Back 8

Yes, the two lobes tha tform its active site cleft swing together by up to 8 A engulfing the glucose like the closing of jaws

Front 9

What would happen if the catalytic and reacting groups were in the poper position for reaction while the enzyme was in the open position?

Back 9

ATP hydrolysis: phosphoryl group transfer to water would be thermodynamically favored

Front 10

What is responsible for the hexokinase's specificity?

Back 10

substrate-induced conformational change and the active site polarity being reduced by the exclusion of water (expediating nucleophilic rxn)

Front 11

What do you call the enzyme that catalyzes the second rxn?

Back 11

phosphoglucose isomerase

Front 12

Phosphoglucose isomerase catalyzes what to what?

Back 12

G6P to fructose-6-phosphate (F6P)

Front 13

What type reaction does phosphoglucose isomerase catalyze?

Back 13

an isomerization rxn of an aldose to a ketose

Front 14

In what form do G6P and F6P predominate?

Back 14

cylic

Front 15

What are the primary steps in the reaction that phosphoglucose isomerase catalyzes?

Back 15

1. Ring opening
2. Isomerization
3. Ring closure

Front 16

What type of catalysis does phosphoglucose isomerase perform?

Back 16

acid-base

Front 17

What is special about the alpha proton on a carbonyl group?

Back 17

it is acidic

Front 18

In the second rxn in glycolysis how is the cis-enediolate intermediate formed?

Back 18

a base abstracts the acidic proton from C2 to form the intermediate

Front 19

In the second rxn in glycolysis which proton is replaced in the overall proton transfer?

Back 19

proton on C1

Front 20

What enzyme catalyzes the third rxn in glycolysis?

Back 20

Phosphofructokinase (PFK)

Front 21

Phosphofructokinase catalyzes what to what?

Back 21

Fructose-6-phosphate (F6P) to Fructose-1,6-biphosphate (FBP)

Front 22

Why is this a biphosphate and not a diphosphate?

Back 22

Because the 2 phosphate groups are not attatched to one another

Front 23

Which rxn is the PFK reaction similar to?

Back 23

hexokinase rxn because the enzyme catalyzes the nucleophilic attack by the C1-OH group of F6P on the electrophilic gamma-phosphorus atom of the Mg2+-ATP complex

Front 24

Why does phophofructokinase play a central role in control of glycolysis?

Back 24

because it catlyzes one of the pathway's rate-determining reactions

Front 25

What can enhance the activity of PFK and what can inhibit the activity of PFK allosterically?

Back 25

PFK can be enhanced by AMP and inhibited allosterically by ATP and citrate

Front 26

Which enzyme catalyzes the fourth step in glycolysis?

Back 26

aldolase

Front 27

Aldolase catalyzes what to what?

Back 27

it cleaves fructose-1,6-biphosphate to form 2 trioses glyceraldehyde-3-phosphate (GAP) and dihydroxyacetone phosphate (DHAP)

Front 28

In the fourth rxn in glycolysis atoms 123 of glucose become what?

Back 28

321 of DHAP (has carbonyl in center)

Front 29

In the fourth rxn in glycolysis atoms 456 of glucose become what?

Back 29

123 of GAP (with carbonyl on outside starting with 1)

Front 30

What type of reaction is reaction 4 of glycolysis?

Back 30

aldol cleavage (retro aldol condensation)

Front 31

What stabilizes the enolate?

Back 31

resonance, as a result of the electron-withdrawing character of the carbonyl oxygen atom

Front 32

What catalyzes aldol cleavage?

Back 32

stabilizing the enolate intermediate through increased electron delocalization

Front 33

What type of mechanism does a nonenzyme catalyzed enol rxn use?

Back 33

base catalysis

Front 34

The aldol cleavage between C3 and C4 of FBP requires a what, and where?

Back 34

a carbonyl at C2 and a hydroxyl at C4

Front 35

Aldol cleavage of G6P yields what types of products?

Back 35

products of unequal carbon chain length

Front 36

Aldol cleavage of FBP results in what?

Back 36

two interconvertible C3 compounds that can therefore enter a common degradative pathway

Front 37

What is a Schiff base?

Back 37

an imine that forms between an amine and an aldehyde or ketone

Front 38

Which enzyme catalyzes reaction five of glycolysis (which is the final stage of part one)?

Back 38

Triose phosphate isomerase

Front 39

What type of isomers are DHAP and GAP? Or F6P and G6P?

Back 39

ketose-aldose isomers

Front 40

Does GAP or DHAP continue in the glycolytic pathway?

Back 40

GAP