Glycolysis

Question 1

What is the reason for phosphorylation of glucose in the hexokinase step?

Answer 1

Phosphorylating six carbon sugars prevents the sugars from leaving the cell and reduces the intracellular glucose concentration so the gradient factors import

Question 2

Direction of the hexokinase reaction

Answer 2

Irreversible

Question 3

Reactants in hexokinase

Answer 3

ATP, Glucose

Question 4

Products in Hexokinase reaction.

Answer 4

ADP, Glucose-6-phosphate and H+

Question 5

What acts as the nucleophile in the hexokinase reaction

Answer 5

CH2OH

Question 6

What happens in the phosphoglucose isomerase reaction?

Answer 6

G-6-P (aldose) is converted to F-6-P (ketose) by phosphoglucose isomerase

Question 7

Reversibility of the phosphoglucose isomerase reaction

Answer 7

Freely reversible; direction depends on concentration of reactants and products

Question 8

How would you drive the forward reaction in phosphoglucose isomerase?

Answer 8

Make a lot of reactants (G6P)

Question 9

How does phosphofructokinase phosphorylation F6P

Answer 9

Chance C-1 from CH2OH to CH2OPO3^2-

Question 10

Reactant of phosphofructokinase rxn

Answer 10

F-6-P and ATP

Question 11

Product of phosphofructokinase rxn

Answer 11

Fructose-1,6-biphosphate (FBP), ADP and H+

Question 12

Reversibility of the phosphofructokinase rxn

Answer 12

Irreversible

Question 13

What is the main difference between F-6-P and FBP

Answer 13

F6P only has one CH2PO3^2- and its on carbon 6 whereas, FBG has one on carbon 1 and carbon 6

Question 14

Evidence that aldolase uses a Schiff base mechanism

Answer 14

Alanine screening of the active site Lys or Asp eliminates enzymatic activity

Question 15

What happens in alanine screening?

Answer 15

The gene for a protein is modified to test the importance of a specific residue

Question 16

What happens when the codon for Lys is changed to Ala

Answer 16

The activity of the expressed proteins is measured, so there will be no activity since Lys is essential to form a schiff base

Question 17

What is alanine screening measuring

Answer 17

It measures enzyme activity w/ and w/o one of the active site amino acid residues mutated to alalnine

Question 18

What are the products of the aldolose rxn

Answer 18

Dihydoxyacetone phosphate and glycerolaldehyde-3-phosphate; Asp and Lys resides

Question 19

Triose Phosphate isomerase

Answer 19

Glyceraldehyde-3-phosphate (GAP) converts to an Enediol intermediate and then to Dihydroxuacetonephosphate (DHAP)

Question 20

What are the enediolate transition state analogs

Answer 20

2-phosphoglycolate and phosphoglycohydroxamate; they bind tightly to triose phosphate isomerase

Question 21

Glyceraldehyde-3-phosphate Dehydrogenase (GAPDH)

Answer 21

GAP is converted to 1-3biphosphoglycerate using NAD+ as a redox cofactor

Question 22

How does Phosphoglycerate Kinase form ATP

Answer 22

1-3Biphosphoglycerate reacts with Mg2+ ADP to make 3-phosphoglycerate and Mg2+-ATP

Question 23

What explains the presence of the active site cys in the GAPDH mechanism?

Answer 23

Suggested by inactivation of the enzyme by idoacetate

Question 24

What is the reactant of the phosphoglycerate mutase step?

Answer 24

3-phosphoglycerate

Question 25

What is the reactant of the phosphoglycerate mutase step?

Answer 25

3-phosphoglycerate

Question 26

What happens in the enolase step

Answer 26

2-Phosphoglycerate (2PG) has a water removed from the lease Enolase to form Phosphoenolpyruvate and water

Question 27

How does pyruvate kinase generate ATP

Answer 27

Phosphoenol-pyruvate (pep) and ADP react with pyruvate kinase to form ATP and pyruvate

Question 28

What happens to pyruvate under anaerobic conditions in animals

Answer 28

Pyruvate is reduced to lactate by lactate dehydrogenase so that NADH can be reoxidized to NAD+ and recycled into GAPDH to continue glycolysis

Question 29

What happens to pyruvate under anaerobic conditions in yeast?

Answer 29

Pyruvate is decarboxylated to acetaldehyde which is then reduced by alcohol dehydrogenase to ethanol so NADH can be reoxidized to NADH+

Question 30

Acetaldehyde

Answer 30

Broken down version of ethanol, contributes to hangovers

Question 31

Pyruvate dehydrogenase

Answer 31

Pyruvate may be converted to acetyl-CoA which is then oxidized further in the CAC or used in lipid synthesis

Question 32

Pyruvate Carboxylase

Answer 32

Pyruvate may be converted to oxaloacetate which can be used for amino acid or glucose biosynthesis

Question 33

What is the cost of gluconeogeneisis

Answer 33

4 ATP + 2 GPT + 2 NADH (But Glycolysis only yields 2 ATP and 2 NADH

Question 34

Where does gluconeogenesis occur

Answer 34

Primarily in the liver and a little in the kidney

Question 35

What happens with the irreversibly reactions of glycolysis during gluconeogenesis?

Answer 35

Irreversible rxns are bypassed

Question 36

How is glycolysis inhibited?

Answer 36

Glycolytic products such as ATP and PEP inhibits glycolysis

Question 37

How is glycolysis activated?

Answer 37

Through molecules that indicate a low energy charge in the cell such as AMP and ADP

Question 38

F26BP

Answer 38

Simultaneously regulates glycolysis and gluconeogenesis by ensuring opposing pathways do not run simultaneously

Question 39

What is F2BP produced by

Answer 39

PFK-2

Question 40

What is F26BP an inhibitor of

Answer 40

The gluconeogenesis enzyme FBPase-1

Question 41

What is F26BP an allosteric activator of

Answer 41

PFK-1 which is responsible for making FBP in step 3

Question 42

Step 1 of glycogen synthesis

Answer 42

Phosphoglucomutase interconverts G6P and G1P

Question 43

What is step 2 of glycogen synthesis

Answer 43

G1P is activated by UTP to form UDP-glucose and PP

Question 44

What drives the reaction of glycogen synthesis forward?

Answer 44

Hydrolysis of PP

Question 45

Step 3 of glycogen synthesis

Answer 45

Glycogen synthase links UDP-glucose units to Glycogen via a(1-4) and UDP functions as a leaving group

Question 46

How are new branches formed in glycogen

Answer 46

Glycogen branching enzyme moved 7 residues from the main chain to form a new branch

Question 47

How is glycogen broken down?

Answer 47

Glycogen phosphorylase use phosphorolysis to break a(1-4) bonds and produce G1P monomers

Question 48

How is glucose removed at the branch points in glycogen

Answer 48

A debranching enzyme moves 3 residues from a 4 glucose residue chain to the main chain and then cleaves the a(1-6) branch point

Question 49

How does the liver increase blood glucose concentration?

Answer 49

Phosphorylated sugars cannot cross the plasma membrane; G^P is converted to glucose for export