Glycolysis

Question 1

Another term for glycolysis?

Answer 1

Embden-Meyerhof-Parnas Pathway

Question 2

What are the two stages and what steps do they span?

Answer 2

Energy investment stage (Steps 1-5)
Energy recovery stage (Steps 6-10)

Question 3

Overall rxn and net ΔG?

Answer 3

glucose + 2 NAD+ + 2 ADP + 2 Pi → 2 pyruvate + 2 NADH + 2 ATP + 2 H2O + 4H+
ΔG = -85 kJ/mol

Question 4

Can metabolites escape the pathway?

Answer 4

No due to lack of transporters

Question 5

In the synthesis of pyruvate, how do the following types treat pyruvate?
1. aerobic
2. hypoxic
3. hypoxic/anaerobic

Answer 5

aerobic: proceeds to TCA cycle (as acetyl) and oxidative phosphorylation
hypoxic: lactic acid fermentation
hypoxic/anaerobic: ethanol fermentation

Question 6

What is bi-bi mechanism?

Answer 6

2 substrates produce 2 products

Question 7

In step 1 of glycolysis, cofactor Mg2+ is needed. Why?

Answer 7

ATP will inhibit hexokinase instead of attacking D-glucose

Question 8

Enzyme, substrate, and product of step 1?

Answer 8

hexokinase, glucose to glucose-6-phosphate (G6P) coupled with ATP to ADP + Pi

Question 9

Enzyme, substrate, and product of step 2?

Answer 9

phosphoglucose isomerase, G6P to fructose-6-phosphate (F6P)

Question 10

Enzyme, substrate, and product of step 3?

Answer 10

phosphofructosekinase-1 (PFK-1), F6P to fructose-1,6-biphosphate (FBP) coupled with ATP to ADP + Pi

Question 11

Enzyme, substrate, and product of step 4?

Answer 11

fructose-1,6-biphosphate aldolase, FBP to Dihydroxyacetone phosphate (DHAP) + Glyceraldehyde-3-phosphate (G3P)

Question 12

Enzyme, substrate, and product of step 5?

Answer 12

triosephosphate isomerase (TIM), DHAP to G3P

Question 13

Enzyme, substrate, and product of step 6?

Answer 13

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), G3P to 1,3-biphosphoglycerate (1,3-BPG) coupled with NAD+ + Pi to NADH + H+

Question 14

Enzyme, substrate, and product of step 7?

Answer 14

phosphoglycerate kinase (PGK), 1,3-BPG to 3-phosphoglycerate (3PG) coupled with ADP to ATP

Question 15

Enzyme, substrate, and product of step 8?

Answer 15

Phosphoglycerate mutase, 3PG to 2-phosphoglycerate (2PG)

Question 16

Enzyme, substrate, and product of step 9?

Answer 16

Enolase, 2PG to phosphoenol pyruvate (PEP)

Question 17

Enzyme, substrate, and product of step 10?

Answer 17

Pyruvate Kinase, PEP to pyruvate (enol) and eventually to pyruvate (keto) coupled with ADP + H+ to ATP

Question 18

In step 2 of glycolysis, why do we need to isomerize G6P to F6P?

Answer 18

Only F6P can yield 2 3C products. G6P yields 1 4C and 1 2C product.

Question 19

Why is step 3 of glycolysis also known as the “first committed step”?

Answer 19

allosteric enhancers and inhibitors are present to enhance or inhibit structure of enzyme

Question 20

Why does step 4 of glycolysis ensure the forward reaction to proceed?

Answer 20

fast removal of products from active site prevents reverse reaction. Very positive ΔG.

Question 21

In step 5 of glycolysis, a ___________ is created to convert DHAP to G3P

Answer 21

enediol intermediate

Question 22

In step 6, to convert G3P to 1,3-BPG, _________ and ________ must occur

Answer 22

phosphorylation and oxidation

Question 23

Step 6 is the start of what stage?

Answer 23

Energy recovery stage

Question 24

Step 7 is coupled with what step?

Answer 24

Step 6

Question 25

Step 8 contains residues at at active site. What is/are this/these?

Answer 25

phospho-His and free His residues

Question 26

What is the purpose of isomerization of 3PG to 2PG?

Answer 26

stability of anion products

Question 27

Highly exergonic step of glycolysis that required the creation of other steps?

Answer 27

Step 9 is highly exergonic that is why step 7-8 is important for stability.

Question 28

What is the final form of the product in step 10?

Answer 28

pyruvate keto form

Question 29

Fates of the pyruvate molecule.

Answer 29

Ethanol fermentation
Lactic acid fermentation
TCA Cycle (as acetyl)

Question 30

What pathway do the following autotrophs undergo?
1. Aerobes
2. Anaerobes

Answer 30

Aerobes : TCA Cycle as Anaerobes : fermentation