Glycolysis

Question 1

Glycolysis net reaction

Answer 1

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

Question 2

2 stages of glycolysis

Answer 2

Hexose stage

Triose stage

Question 3

Differences in ATP usage between hexose stage and triose stage

Answer 3

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

Question 4

Step 1 of glycolysis

Answer 4

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

Question 5

Isoforms

Answer 5

Different structures of an enzyme that have the same function

Question 6

Step 2 of glycolysis

Answer 6

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

Question 7

Stereospecificity of step 2

Answer 7

Highly stereospecific: C-2 epimer isn’t formed

Question 8

Step 3 of glycolysis

Answer 8

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

Question 9

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

Answer 9

Beta form

Alpha anomer from step 3 must undergo conformational change

Question 10

First committed step of glycolysis

Answer 10

Step 3

Question 11

Step 4 of glycolysis

Answer 11

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

Question 12

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

Answer 12

DHAP is derived from C1 to C3 of fructose

G3P is derived from C4 to C6 of fructose

Question 13

Step 5 of glycolysis

Answer 13

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

Question 14

Step 6 of glycolysis

Answer 14

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

Question 15

Redox reaction in step 6

Answer 15

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

Question 16

Step 7 of glycolysis

Answer 16

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

Question 17

First ATP-generating step of glycolysis

Answer 17

Step 7

Question 18

Substrate level phosphorylation

Answer 18

Molecule directly transfers phosphoryl group to ADP

Question 19

Step 8 of glycolysis

Answer 19

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

Question 20

Mutases

Answer 20

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

Question 21

Mutase mechanism

Answer 21

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

Question 22

Step 9 of glycolysis

Answer 22

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

Question 23

Step 10 of glycolysis

Answer 23

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

Question 24

Metabolically irreversible steps of glycolysis

Answer 24

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)

Question 25

Metabolism of pyruvate to ethanol: what it achieves

Answer 25

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

Question 26

2 reactions of pyruvate to ethanol

Answer 26

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

Question 27

Reduction of pyruvate to lactate

Answer 27

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

Question 28

Free energy equation

Answer 28

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

Question 29

Glycolysis using fructose

Answer 29

Fructose is converted into 2 G3P: 2 ATP are invested

Question 30

Glycolysis using galactose

Answer 30

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

Question 31

Glycolysis using mannose

Answer 31

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