Glycolysis

Question 1

What is glycolysis?

Answer 1

a series of biochemical reactions by which glucose is converted to pyruvate (or lactate), releasing energy in the process

Question 2

Glycolysis has 2 phases. Name them.

Answer 2

preparatory phase

payoff phase

Question 3

What happens in the preparatory phase? (general overview)

Answer 3

glucose —- F-1,6-BP—– G-3-P

Question 4

What happens in the payoff phase? (general overview)

Answer 4

G-3-P—pyruvate or lactate

Question 5

What is the net gain of ATP in glycolysis and how does it balance to this?

Answer 5

net gain of 2ATP

4ATP produced in payoff phase, but 2ATP required in preparatory phase

Question 6

How many steps are there overall in glycolysis?

Answer 6

10

Question 7

What is the first step of glycolysis and what enzyme is involved? Importance?

Answer 7

conversion of glucose to glucose-6-phosphate by hexokinase

irreversible

Question 8

What is the second step of glycolysis? Importance?

Answer 8

conversion of G-6-P to F-6-P

readily reversible

Question 9

What is the 3rd step of glycolysis? Importance? Catalyst?

Answer 9

conversion of F-6-P to F-1,6BP
irreversible
catalysed by phosphofructokinase-1

Question 10

What happens in step 4 of glycolysis? Importance?

Answer 10

cleavage of F-1,6BP to triose sugars
one is DHP and one is G-3-P
readily reversible

Question 11

What happens in step 5 of glycolysis? Importance?

Answer 11

interconversion of trios sugars
DHP converted to G-3-P (glyceraldehyde - 3-phosphate)
readily reversible

Question 12

What happens in step 6 of glycolysis? Catalyst? Importance?

Answer 12

conversion of G-3-P to 1,3-PG
catalysed by G-3-P dehydrogenase
2NADH produced!

Question 13

What happens in step 7 of glycolysis? Catalyst? Importance?

Answer 13

1,3-PG converted to 3-PG
phosphoglycerate kinase
2ATP produced!!

Question 14

What happens at step 8 of glycolysis? Importance?

Answer 14

3-PG converted to 2-PG

reversible

Question 15

What happens in step 9 of glycolysis? Importance?

Answer 15

2-PG converted to PEP

reversible

Question 16

What happens in step 10 of glycolysis? Catalyst? Importance?

Answer 16

PEP converted to pyruvate
catalyst pyruvate kinase
2ATP produced!!

Question 17

What are the most important steps in glycolysis? State briefly why they are important.

Answer 17

Step 1 - glucose to G-6-P, irreversible
Step 3 - F-6-P to F-1,6BP, irreversible
Step 6 - G-3-P to 1,3PG, produces 2NADH
Step 7 - 1,3PG to 3PG, 2ATP produced
Step 10 - PEP to pyruvate, 2ATP produced

Question 18

Why does NAD+ need to be regenerated?

Answer 18

for reduction of various intermediate metabolites

Question 19

What happens to pyruvate at the end of glycolysis?

Answer 19

• converted to ethanol (fermentation in yeast)
• used in citric acid cycle (after being converted to acetyl CoA in aerobic conditions)
• converted to lactate in anaerobic conditions in exercising skeletal muscle

Question 20

What is the Cori Cycle?

Answer 20

interaction between muscle and liver to compensate for the oxygen debt when muscles respire anaerobically (liver converts lactate to glucose)