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Biochemistry > Week 5: Glycolysis > Flashcards

Week 5: Glycolysis Flashcards

(52 cards)

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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?

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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?

Study These Flashcards
A

Product (GAP) concentration kept low to pull reaction forward

23
Q

What occurs during Triose Phosphate Interconversion?

Study These Flashcards
A

Dihydroxyacetone isomerize to GAP by triode phosphate isomerase

24
Q

What is the rationale behind Triose Phosphate Interconversion?

Study These Flashcards
A

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

25
Why is Triose Phosphate Interconversion reversible?
GAP concentration kept low to pull reaction forward
26
What occurs during Oxidation of Glyceraldehyde 3-Phosphate?
GAP + Pi are catalyzed by GAP dehydrogenase and NAD+ to 1,3-bisphosphoglycerate
27
What is the rationale for Oxidation of Glyceraldehyde 3-Phosphate ?
1. Incorporates inorganic phosphate 2. Generates a high-energy phosphate compound 3. Allows for net production of ATP via glycolysis
28
How is Oxidation of GAP reversible?
Coupled to next reaction to pull forward
29
What occurs during the 1st Production of ATP?
1,3-bisphosphoglycerate pairs with ADP and Mg++ to form ATP and 3-Phosphoglycerate by Phosphoglycerate kinase
30
What is the rationale for 1st Production of ATP?
Substrate-level phosphorylation to make ATP
31
What enzyme transfer phosphate groups
Kinases
32
What occurs during the Migration of the Phosphate?
3-Phosphoglycerate is catalyzed by phosphoglycerate mutate and Mg++ to form 2-Phosphoglycerate
33
What is the rationale for Migration of the Phosphate?
Generate a high-energy phosphate compound
34
What enzyme catalyze the migration of functional groups within the same molecule?
Mutases
35
What makes Migration of the Phosphate reversible?
Reactant concentration kept high by phosphoglycerate kinase to push reaction forward
36
What occurs during the Dehydration of 2-PG?
2-PG is dehydrated by enolase to form PEP
37
What is the rationale of Dehydration of 2-PG?
Generate a high-energy phosphate compound
38
Why is Dehydration of 2-PG reversible?
Product concentration kept low to pull forward
39
What occurs during the 2nd Production of ATP?
PEP + ADP is initiated by Mg++, K+ and pyruvate kinase to make ATP and pyruvate
40
What is the rationale for 2nd Production of ATP?
1. substrate-level phosphorylation to make ATP | 2. Net production of 2 ATP/glucose
41
What makes the 2nd Production of ATP irreversible?
1. Regulated by ATP, divalent metals, and other metabolites | 2. Activated by feed forward regulation by fructose 1,6-bisphosphate
42
What is used in glycolysis?
1 glucose, 2 ATP; 2 NAD+
43
What is made in glycolysis?
2 pyruvate 4 ATP 2 NADH
44
Why is glycolysis heavily regulated?
1. Ensure proper use of nutrients | 2. Ensure production of ATP only when needed
45
What enzyme cleaves glycogen and starch
Glycogen phosphorylase
46
What are components of lactose
Glucose and galactose
47
What are the components of sucrose?
Glucose and fructose
48
What occurs during fermentation?
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
What enzyme reduces pyruvate to lactate?
Lactate dehydrogenase
50
What is coenzyme is used for fermentation?
NADH
51
What is produced during aerobic glycolysis?
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
What is produced during anaerobic glycolysis?
1. Produces 2 ATP | 2. 2 NADH are recycled to NAD+ by lactate dehydrogenase

Biochemistry (16 decks)

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