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Flashcards in Glycolysis Deck (31):
1

Glycolysis net reaction

Glucose + 2 ADP + 2 NAD+ + 2 Pi -> 2 pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O

2

2 stages of glycolysis

Hexose stage
Triose stage

3

Differences in ATP usage between hexose stage and triose stage

Hexose stage consumes ATP, but triose stage regenerates more ATP than what was consumed

4

Step 1 of glycolysis

Transfer of phosphoryl group from ATP to glucose
Takes place at primary alcohol (most nucleophilic)
Glucose -> glucose 6-phosphate
Enzymes: hexokinase and glucokinase

5

Isoforms

Different structures of an enzyme that have the same function

6

Step 2 of glycolysis

Isomerization: aldose to ketose (proceeds through open-chain form that is generated within the enzyme active site)
Glucose 6-phosphate -> fructose 6-phosphate
Enzyme: glucose 6-phosphate isomerase

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Stereospecificity of step 2

Highly stereospecific: C-2 epimer isn't formed

8

Step 3 of glycolysis

Transfer of a 2nd phosphoryl group from ATP to fructose 6-phosphate
Fructose 6-phosphate -> fructose 1,6-bisphosphate
Enzyme: phosphofructokinase-1

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Anomeric form of fructose 6-phosphate that phosphofructokinase-1 prefers

Beta form
Alpha anomer from step 3 must undergo conformational change

10

First committed step of glycolysis

Step 3

11

Step 4 of glycolysis

C3-C4 bond cleavage, yielding 2 triose phosphates
Fructose 1,6-bisphosphate -> dihydroxyacetone phosphate and glyceraldehyde 3-phosphate
Eznyme: aldolase

12

Portions of fructose 1,6-bisphosphate that DHAP and G3P are derived from

DHAP is derived from C1 to C3 of fructose
G3P is derived from C4 to C6 of fructose

13

Step 5 of glycolysis

Rapid interconversion of triose phosphates
DHAP -> G3P
Enzyme: triose phosphate isomerase

14

Step 6 of glycolysis

Oxidation and phosphorylation, yielding a high-energy mixed-acid anhydride
G3P -> 1,3-bisphosphoglycerate
Enzyme: glyceraldehyde 3-phosphate dehydrogenase

15

Redox reaction in step 6

Generation of H+ (NAD+ -> NADH + H+)

16

Step 7 of glycolysis

Transfer of a high-energy phosphoryl group to ADP, yielding ATP
1,3-bisphosphoglycerate -> 3-phosphoglycerate
Enzyme: phosphoglycerate kinase

17

First ATP-generating step of glycolysis

Step 7

18

Substrate level phosphorylation

Molecule directly transfers phosphoryl group to ADP

19

Step 8 of glycolysis

Intramolecular phosphoryl group transfer
3-phosphoglycerate -> 2-phosphoglycerate
Enzyme: phosphoglycerate mutase

20

Mutases

Class of isomerase that catalyze transfer of a phosphoryl group from 1 part of a molecule to another

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Mutase mechanism

Enzyme phosphoryl intermediate: phosphoryl group is transferred to enzyme and then transferred back to substrate

22

Step 9 of glycolysis

Dehydration to an energy-rich enol ester
2-phosphoglycerate -> phosphoenolpyruvate
Enzyme: enolase

23

Step 10 of glycolysis

Transfer of a high-energy phosphoryl group to ADP, yielding ATP
Phosphoenolpyruvate -> pyruvate
Enzyme: pyruvate kinase

24

Metabolically irreversible steps of glycolysis

Step 1 (glucose -> glucose 6-phosphate)
Step 3 (fructose 6-phosphate -> fructose 1,6-bisphosphate)
Step 7 (1,3-bisphosphoglycerate -> 3-phosphoglycerate)
Step 10 (phosphoenolpyruvate -> pyruvate)

25

Metabolism of pyruvate to ethanol: what it achieves

Survival mechanism of some organisms in long-term anaerobic conditions
Regenerates NAD+ needed for modest energy production

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2 reactions of pyruvate to ethanol

1. Decarboxylation of pyruvate to acetaldehyde (pyruvate decarboxylase)
2. Reduction of acetaldehyde to ethanol (alcohol dehydrogenase)

27

Reduction of pyruvate to lactate

Lactate dehydrogenase (NADH cofactor) reduces pyruvate to L-lactate
Short-term anaerobic conditions: regeneration of NAD+ in the absence of oxygen
Lactic acid is eventually moved from the muscles to the liver to be converted back to pyruvate

28

Free energy equation

delta G= delta G0 + RTln(Q)
Q= current reaction quotient

29

Glycolysis using fructose

Fructose is converted into 2 G3P: 2 ATP are invested

30

Glycolysis using galactose

Galactose is converted into glucose 1-phosphate through UDP-glucose (galactose is traded for glucose)

31

Glycolysis using mannose

Mannose is converted into fructose 6-phosphate (aldose -> ketose)