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BCHM Exam 3 > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

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

A

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

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2
Q

Direction of the hexokinase reaction

A

Irreversible

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3
Q

Reactants in hexokinase

A

ATP, Glucose

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4
Q

Products in Hexokinase reaction.

A

ADP, Glucose-6-phosphate and H+

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5
Q

What acts as the nucleophile in the hexokinase reaction

A

CH2OH

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6
Q

What happens in the phosphoglucose isomerase reaction?

A

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

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7
Q

Reversibility of the phosphoglucose isomerase reaction

A

Freely reversible; direction depends on concentration of reactants and products

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8
Q

How would you drive the forward reaction in phosphoglucose isomerase?

A

Make a lot of reactants (G6P)

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9
Q

How does phosphofructokinase phosphorylation F6P

A

Chance C-1 from CH2OH to CH2OPO3^2-

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10
Q

Reactant of phosphofructokinase rxn

A

F-6-P and ATP

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11
Q

Product of phosphofructokinase rxn

A

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

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12
Q

Reversibility of the phosphofructokinase rxn

A

Irreversible

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13
Q

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

A

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

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14
Q

Evidence that aldolase uses a Schiff base mechanism

A

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

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15
Q

What happens in alanine screening?

A

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

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16
Q

What happens when the codon for Lys is changed to Ala

A

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

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17
Q

What is alanine screening measuring

A

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

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18
Q

What are the products of the aldolose rxn

A

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

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19
Q

Triose Phosphate isomerase

A

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

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20
Q

What are the enediolate transition state analogs

A

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

21
Q

Glyceraldehyde-3-phosphate Dehydrogenase (GAPDH)

A

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

22
Q

How does Phosphoglycerate Kinase form ATP

A

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

23
Q

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

A

Suggested by inactivation of the enzyme by idoacetate

24
Q

What is the reactant of the phosphoglycerate mutase step?

A

3-phosphoglycerate

25
Q

What is the reactant of the phosphoglycerate mutase step?

A

3-phosphoglycerate

26
Q

What happens in the enolase step

A

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

27
Q

How does pyruvate kinase generate ATP

A

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

28
Q

What happens to pyruvate under anaerobic conditions in animals

A

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

29
Q

What happens to pyruvate under anaerobic conditions in yeast?

A

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

30
Q

Acetaldehyde

A

Broken down version of ethanol, contributes to hangovers

31
Q

Pyruvate dehydrogenase

A

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

32
Q

Pyruvate Carboxylase

A

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

33
Q

What is the cost of gluconeogeneisis

A

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

34
Q

Where does gluconeogenesis occur

A

Primarily in the liver and a little in the kidney

35
Q

What happens with the irreversibly reactions of glycolysis during gluconeogenesis?

A

Irreversible rxns are bypassed

36
Q

How is glycolysis inhibited?

A

Glycolytic products such as ATP and PEP inhibits glycolysis

37
Q

How is glycolysis activated?

A

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

38
Q

F26BP

A

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

39
Q

What is F2BP produced by

A

PFK-2

40
Q

What is F26BP an inhibitor of

A

The gluconeogenesis enzyme FBPase-1

41
Q

What is F26BP an allosteric activator of

A

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

42
Q

Step 1 of glycogen synthesis

A

Phosphoglucomutase interconverts G6P and G1P

43
Q

What is step 2 of glycogen synthesis

A

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

44
Q

What drives the reaction of glycogen synthesis forward?

A

Hydrolysis of PP

45
Q

Step 3 of glycogen synthesis

A

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

46
Q

How are new branches formed in glycogen

A

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

47
Q

How is glycogen broken down?

A

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

48
Q

How is glucose removed at the branch points in glycogen

A

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

49
Q

How does the liver increase blood glucose concentration?

A

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

BCHM Exam 3 (7 decks)

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