Glycolysis

Question 1

Hexokinase

Answer 1

Uses the energy of ATP to phosphorylate glucose into glucose-6-phosphate, thus trapping it in the cell

Question 2

Phosphoglucose isomerase (glucose-6-phosphate isomerase)

Answer 2

Converts glucose-6-phosphate to fructose-6-phosphate

Question 3

Phosphofructokinase (PFK-1)

Answer 3

Adds a second phosphate (from ATP) onto fructose-6-phosphate, thus converting it to fructose-1,6-bisphosphate

Question 4

Aldolase

Answer 4

Cleaves fructose-1,6-bisphosphate to two triose phosphates (GAP, DHAP)

Question 5

Triose Phosphate Isomerase (TIM)

Answer 5

Interconverts between DHAP and GAP. Note that this reaction is unfavorable, but GAP is being siphoned off, which means DHAP has a higher concentration than GAP which drivers DHAP -> GAP

Question 6

What are the irreversible steps in the INVESTMENT phase of glycolysis?

Answer 6

1) hexokinase

3) phosphofructokinase

Question 7

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH)

Answer 7

Couples NAD+ reduction to the generation of 1,3-BPG (an intermediate with high phosphoryl transfer potential)

Question 8

Phosphoglycerate kinase (PGK)

Answer 8

PGK performs the first substrate-level phosphorylation in glycolysis (by removing a phosphate group from BPG and adding an ADP to form ATP)

Question 9

What is substrate-level phosphorylation?

Answer 9

Direct transfer of a phosphate group to ADP to form ATP

Question 10

Phosphoglycerate mutase (PGM)

Answer 10

Moves the phosphate from 3PG to the alpha carbon, thus forming 2PG. This is a setup reaction for the next step.

Question 11

Enolase

Answer 11

Dehydrates 2PG to form PEP (very high phosphoryl transfer potential!)

Question 12

Pyruvate kinase (PK)

Answer 12

Performs another substrate-level phosphorylation by pulling a phosphate off of PEP, and generating pyruvate

Question 13

What steps in glycolysis are irreversible?

Answer 13

1 (hexokinase)
3 (phosphofructokinase)
10 (pyruvate kinase)

Question 14

What steps in glucose involve substrate-level phosphorylation?

Answer 14

Phosphoglycerate kinase (PGK) and pyruvate kinase

Question 15

Besides the TCA cycle, name 2 possible fates of pyruvate.

Answer 15

1. Lactate fermentation

2. Ethanol fermentation

Question 16

True or false: When oxygen is scarce, LDH reduces pyruvate using NADH, producing lactate and regenerating NAD+ for glycolysis

Answer 16

True

Question 17

Which steps make ATP?

Answer 17

7 (PGK), 10 (Pyruvate kinase)

Question 18

Which steps use ATP?

Answer 18

1 (Hexokinase), 3 (Phosphofructokinase)