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Biochemistry II > Glycolysis II > Flashcards

Glycolysis II Flashcards

1
Q

What are the last five intermediates of glycolysis?

A
  1. 1,3-bisphosphoglycerate
  2. 3-phosphoglycerate
  3. Phosphoglycerate
  4. Phosphoenolpyruvate
  5. Pyruvate
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2
Q

The last five steps of glycolysis are sometimes called the “_________________ _____________” phase.

A

Energy payoff

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3
Q

The sixth step of glycolysis converts glyceraldehyde-3-phosphate to ________________________________________________ via __________ __________________________________.

A

1,3-bisphosphoglycerate

GAP dehydrogenase

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4
Q

What is the mechanism for GAP dehydrogenase?

A

Redox reaction

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5
Q

As a redox reaction, step 6 of glycolysis requires what cofactor?

A

NAD+

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6
Q

What amino acid residue acts as a nucleophile in GAP dehydrogenase?

A

Cysteine

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7
Q

What is the enzyme that catalyzes the formation of 1,3-bisphosphoglycerate from glyceraldehyde-3-phosphate?

A

GAP dehydrogenase

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8
Q

What is the mechanism for glyceraldehyde-3-phosphate (GAP) dehydrogenase?

A
  1. The cysteine residue in the enzyme acts as a nucleophile and attacks the carbonyl carbon at C1
  2. This attack ultimately kicks out a hydride, which then attacks the NAD+ molecule
  3. The enzyme is covalently bound to the molecule; an inorganic phosphate attacks the carbonyl carbon at C1, expelling the enzyme
  4. 1,3-bisphosphoglycerate is formed
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9
Q

In addition to being a redox reaction, the sixth step of glycolysis - the formation of 1,3BPG - also involves what type of catalysis?

A

Covalent catalysis

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10
Q

The sixth step of glycolysis requires the cofactor NAD+ and what other molecule to form 1,3-bisphosphoglycerate from glyceraldehyde-3-phosphate?

A

Inorganic phosphate

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11
Q

What is the seventh step of glycolysis?

A

The formation of 3-phosphoglycerate from 1,3-bisphosphoglycerate via phosphoglycerate kinase

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12
Q

Is the sixth step of glycolysis reversible?

A

Yes

  1. The cysteine residue in the enzyme acts as a nucleophile, attacking the C1 of carbonyl and expelling inorganic phosphate
  2. The lone pair of electrons on the nitrogen atom in NADH move and expel a hydride ion, which attacks the enzyme-transition state intermediate carbonyl and ultimately “kicks out” the enzyme
  3. Glyceraldehyde-3-phosphate has been reformed
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13
Q

What position does glyceraldehyde-3-phosphate dehydrogenase prefer on NADH: the proR or the proS?

A

ProS

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14
Q

What enzyme catalyzes the seventh step of glycolysis - the formation of 3-phosphoglycerate from 1,3-bisphosphoglycerate?

A

Phosphoglycerate kinase

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15
Q

What type of phosphorylation does the seventh step of glycolysis catalyze?

A

Substrate-level phosphorylation of ADP to ATP

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16
Q

What is the mechanism of phosphoglycerate kinase?

A

Phosphoryl transfer - nucleophilic attack of the acyl phosphate on 1,3-bisphosphoglycerate by the oxygen atom on ADP’s beta phosphate group

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17
Q

Phosphoglycerate kinase is named for its reverse direction. What is the mechanism for the reverse?

A
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18
Q

The eighth step of glycolysis converts 3-phosphoglycerate to 2-phosphoglycerate. What enzyme catalyzes this reaction?

A

Phosphoglycerate mutase

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19
Q

Phosphoglycerate mutase requires a phosphorylated amino acid residue in its active site to function. What amino acid residue is it?

A

Histidine

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20
Q

What is the mechanism for the eighth step of glycolysis catalyzed by phosphoglycerate mutase?

A

A phosphoryl shift

  1. A deprotonated histidine residue abstracts a proton from the hydroxyl group on C2
  2. An oxygen atom acts as a nucleophile and attacks the electrophilic phosphorus on the phosphohistidine residue
  3. The dephosphorylated histidine then attacks the phosphate group on C3, restoring its phosphorylated status, and oxygen picks up a proton from the other protonated histidine residue
21
Q

What intermediate produced in the eighth step of glycolysis is also important in regulating hemoglobin?

A

2,3-bisphosphoglycerate

22
Q

The ninth step of glycolysis forms the high-energy compound ______________________.

A

Phosphoenolpyruvate

23
Q

The formation of phosphoenolpyruvate is catalyzed by what enzyme?

A

Enolase

24
Q

What is the mechanism of action for enolase?

A

Dehydration and general-acid catalysis

25
Q

Enolase requires a metal ion. What metal ion does it require?

A

Mg2+

26
Q

What is the reverse mechanism for phosphoglycerate mutase?

A
27
Q

What is the role of Mg2+ in the enolase mechanism?

A

It makes the proton even more acidic

28
Q

What is the point of forming phosphoenolpyruvate?

A

It is a high energy compound that can be used to make ATP - 2-phosphoglycerate cannot

29
Q

What is the mechanism for enolase?

A
  1. A lysine residue abstracts the proton from C2, forming an unstable carbanion
  2. The lone pair delocalizes to the oxygen atom of the carbonyl group, which is stabilized by the magnesium ion
  3. The oxygen atom “kicks back” and expels water from C3 by deprotonating a glutamate residue
  4. Phosphoenolpyruvate is formed
30
Q

What two amino acid residues are required for enolase activity?

A

Histidine

Glutamate

31
Q

What is the last step of glycolysis?

A

The formation of pyruvate from phosphoenolpyruvate via pyruvate kinase

32
Q

What enzyme catalyzes the last step of glycolysis?

A

Pyruvate kinase

33
Q

Why type of reaction does pyruvate kinase catalyze?

A

A phosphoryl transfer

34
Q

What is the reaction mechanism for the last step of glycolysis?

A
35
Q

Identify the structure.

A

1,3-bisphosphoglycerate

36
Q

Identify the structure.

A

3-phosphoglycerate

37
Q

Identify the structure.

A

2-phosphoglycerate

38
Q

Identify the structure.

A

Phosphoenolpyruvate

39
Q

Identify the structure.

A

Pyruvate

40
Q

What is 1,3BPG?

A

1,3-bisphosphoglycerate

41
Q

What is 3-PG?

A

3-phosphoglycerate

42
Q

What is 2-PG

A

2-phosphoglycerate

43
Q

What is PEP?

A

Phosphoenolpyruvate

44
Q

Which step of the last five steps of glycolysis requires NAD+?

A

The conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate by glyceraldehyde-3-phosphate dehydrogenase

45
Q

Which steps of the last five steps of glycolysis produce ATP via substrate-level phosphorylation?

A
  1. The conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate by phosphoglycerate kinase
  2. The coversion of phosphoenolpyruvate to pyruvate by pyruvate kinase
46
Q

Which step in the last five steps of glycolysis releases water?

A

The conversion of 2-phosphoglycerate to phosphoenolpyruvate via enolase

47
Q

The class I aldolase reaction is the reverse of an _________ _______________________:

  1. The carbonyl reacts with an active-site _________ residue to form the enzyme-substrate intermediate
  2. A double bond forms between nitrogen and C2, releasing water as a byproduct; the resultant imine or _________ base stabilizes the carbanion generated by bond cleavage as an imine delocalizes electrons even better than a carbonyl
  3. Bond cleavage releases ______-___-_____________ as the first product
  4. The resulting ______________ covalently linked to the enzyme is isomerized to a protonated ______ base
  5. Hydrolysis of the ______ base generates dihydroxyacetone phosphate as the second product
A
  • Aldol condensation
  • Lysine residue
  • Schiff base
  • Glyceraldehyde-3-phosphate
  • Enamine
  • Schiff base
  • Schiff base
48
Q

What is the difference between an imine and an enamine?

A

An imine has a double bond between a nitrogen and a carbon; an enamine has a double bond between a carbon and a carbon

Biochemistry II (19 decks)

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