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Biochemistry > Week 5: Glycolysis > Flashcards

Week 5: Glycolysis Flashcards

1
Q

What is glycolysis?

A

The sequence of enzyme-catalyzed reactions by which glucose is converted into pyruvate

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2
Q

How do we extract free energy from glucose aerobically or anaerobically?

A

First: Activate it by phosphorylation.

Second: Collect energy from the high-energy metabolites.

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3
Q

What are the 2 phases of glycolysis?

A
  1. Preparatory

2. Payoff

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4
Q

What step reactions are within the preparatory phase?

A
  1. Phosphorylation of Glucose
  2. Phosphohexose Isomerization
  3. 2nd Priming Phosphorylation
  4. Aldol Cleavage of F-1,6-bP
  5. Triose Phosphate Interconversion
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5
Q

What step reactions are in the payoff phase?

A
  1. Oxidation of Glyceraldehyde 3-Phosphate
  2. 1st Production of ATP
  3. Migration of the Phosphate
  4. Dehydration of 2-PG to PEP
  5. 2nd Production of ATP
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6
Q

What occurs during the phosphorylation of glucose?

A

Glucose phosphorylated by hexokinase to G6P

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7
Q

What energy molecules are used during the phosphorylation of glucose?

A

ATP and Mg++ shields its negative charge

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8
Q

What is the rationale behind the phosphorylation of glucose?

A
  1. Traps glucose inside cell by giving it a negative charge

2. Lowers intracellular glucose concentration to allow further uptake

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9
Q

What make the phosphorylation of glucose irreversible?

A
  1. Regulated mainly by products
  2. Hexokinase is allostericly inhibited by glucose-6-phosphate
  3. Glucokinase is activated by glucose (feedforward) and inhibited by fructose 6-phosphate
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10
Q

What the difference between hexokinase and glucokinase?

A

Hex: has a high affinity for glucose
Glu: has a low affinity for glucose

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11
Q

What is the purpose for glucokinase?

A

Plays an important role in controlling blood glucose levels since it is only active when glucose is high
Stimulates insulin release

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12
Q

What occurs during Phosphohexose Isomerization?

A

G6P is isomerized by phospohexose isomerase to F6P

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13
Q

What is the rationale behind Phosphohexose Isomerization?

A
  1. C1 of fructose is easier to phosphorylate by PFK

2. Allows for symmetrical cleavage by aldolase

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14
Q

Is Phosphohexose Isomerization reversible?

A

Yes

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15
Q

Does Phosphohexose Isomerization require Mg++?

A

Yes

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16
Q

What occurs during 2nd Priming Phosphorylation?

A

F6P is phosphorylated by PFK-1, ATP, and Mg+++ into Fructose 1,6-bidphosphate

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17
Q

What is the rationale behind 2nd Priming Phosphorylation ?

A
  1. Further activation of glucose

2. allows for 1 phosphate/3-carbon sugar after step 4

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18
Q

Which step would be the first committed step of glycolysis?

A

2nd Priming Phosphorylation by Phosphofructokinase-1

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19
Q

Why is 2nd Priming Phosphorylation by Phosphofructokinase-1 irreversible?

A

Phosphofructokinase-1 is highly regulated.
Allosterically inhibited by ATP and citrate
Allosterically activated by AMP and ADP

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20
Q

What occurs during Aldol Cleavage of F-1,6-bP?

A

Fructose cleaves into GAP and Dihydroxyacetone by aldolase

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21
Q

What is the rationale for Aldol Cleavage of F-1,6-bP?

A
  1. Six-carbon sugar is cleaved into two three-carbon sugars.

2. High-energy phosphate trioses

22
Q

Why Aldol Cleavage of F-1,6-bP by Aldolase reversible?

A

Product (GAP) concentration kept low to pull reaction forward

23
Q

What occurs during Triose Phosphate Interconversion?

A

Dihydroxyacetone isomerize to GAP by triode phosphate isomerase

24
Q

What is the rationale behind Triose Phosphate Interconversion?

A

Allows glycolysis to proceed to payoff phase by a single chemical pathway

25
Q

Why is Triose Phosphate Interconversion reversible?

A

GAP concentration kept low to pull reaction forward

26
Q

What occurs during Oxidation of Glyceraldehyde 3-Phosphate?

A

GAP + Pi are catalyzed by GAP dehydrogenase and NAD+ to 1,3-bisphosphoglycerate

27
Q

What is the rationale for Oxidation of Glyceraldehyde 3-Phosphate ?

A
  1. Incorporates inorganic phosphate
  2. Generates a high-energy phosphate compound
  3. Allows for net production of ATP via glycolysis
28
Q

How is Oxidation of GAP reversible?

A

Coupled to next reaction to pull forward

29
Q

What occurs during the 1st Production of ATP?

A

1,3-bisphosphoglycerate pairs with ADP and Mg++ to form ATP and 3-Phosphoglycerate by Phosphoglycerate kinase

30
Q

What is the rationale for 1st Production of ATP?

A

Substrate-level phosphorylation to make ATP

31
Q

What enzyme transfer phosphate groups

A

Kinases

32
Q

What occurs during the Migration of the Phosphate?

A

3-Phosphoglycerate is catalyzed by phosphoglycerate mutate and Mg++ to form 2-Phosphoglycerate

33
Q

What is the rationale for Migration of the Phosphate?

A

Generate a high-energy phosphate compound

34
Q

What enzyme catalyze the migration of functional groups within the same molecule?

A

Mutases

35
Q

What makes Migration of the Phosphate reversible?

A

Reactant concentration kept high by phosphoglycerate kinase to push reaction forward

36
Q

What occurs during the Dehydration of 2-PG?

A

2-PG is dehydrated by enolase to form PEP

37
Q

What is the rationale of Dehydration of 2-PG?

A

Generate a high-energy phosphate compound

38
Q

Why is Dehydration of 2-PG reversible?

A

Product concentration kept low to pull forward

39
Q

What occurs during the 2nd Production of ATP?

A

PEP + ADP is initiated by Mg++, K+ and pyruvate kinase to make ATP and pyruvate

40
Q

What is the rationale for 2nd Production of ATP?

A
  1. substrate-level phosphorylation to make ATP

2. Net production of 2 ATP/glucose

41
Q

What makes the 2nd Production of ATP irreversible?

A
  1. Regulated by ATP, divalent metals, and other metabolites

2. Activated by feed forward regulation by fructose 1,6-bisphosphate

42
Q

What is used in glycolysis?

A

1 glucose, 2 ATP; 2 NAD+

43
Q

What is made in glycolysis?

A

2 pyruvate
4 ATP
2 NADH

44
Q

Why is glycolysis heavily regulated?

A
  1. Ensure proper use of nutrients

2. Ensure production of ATP only when needed

45
Q

What enzyme cleaves glycogen and starch

A

Glycogen phosphorylase

46
Q

What are components of lactose

A

Glucose and galactose

47
Q

What are the components of sucrose?

A

Glucose and fructose

48
Q

What occurs during fermentation?

A
  1. Generation of energy (ATP) without consuming oxygen
  2. Reduction of pyruvate to another product (alcohol or lactate)
  3. Regenerates NAD+ for further glycolysis under anaerobic conditions
49
Q

What enzyme reduces pyruvate to lactate?

A

Lactate dehydrogenase

50
Q

What is coenzyme is used for fermentation?

A

NADH

51
Q

What is produced during aerobic glycolysis?

A
  1. Produces 2 ATP and 2 NADH

2. NADH is converted to ATP in the electron transport chain (ultimately gain 2.5 ATP per NADH)

52
Q

What is produced during anaerobic glycolysis?

A
  1. Produces 2 ATP

2. 2 NADH are recycled to NAD+ by lactate dehydrogenase

Biochemistry (16 decks)

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