Glycolysis

How many steps is glycolysis?

10 steps

Where does glycolysis occur?

cytoplasm

Does glycolysis require oxygen?

No, it is anaerobic

How many enzymes are involved in glycolysis?

10 enzymes

What are the products of glycolysis?

2 pyruvate, 2 NADH, 2 ATP, 2 H2O

How much ATP is produced directly during glycolysis?

4 ATP produces, 2 ATP consumed

What molecule carries electrons during glycolysis?

NAD+ → NADH

Which glycolysis steps consume ATP?

Step 1 (Hexokinase) and Step 3 (PFK-1)

What enzyme catalyzes Step 1 of glycolysis?

Hexokinase (Glucokinase)

What reaction occurs in step 1?

Glucose → Glucose-6-Phosphate

What does the enzyme do in Step 1?

Hexokinase transfers phosphate from ATP to Glucose

What are the irreversible steps of glycolysis?

1,3,10

What is glucokinase?

Liver enzyme that phosphorylates glucose when blood glucose levels are high

What enzyme catalyzes step 2?

Phosphoglucose Isomerase

What reaction occurs in step 2?

Glucose-6-phosphate → Fructose-6-phosphate

What enzyme catalyzes step 3?

Phosphofructokinase-1 (PFK-1)

What does Phosphofructokinase-1 (PFK-1) do?

Transfers a phosphate group from ATP to fructose-6-phosphate

What reaction occurs in step 3?

Fructose-6-Phosphate → Fructose-1,6,-bisphosphate

What is the rate-limiting step?

Step 3

What is the most important regulatory enzyme of glycolysis?

Phosphofructokinase (PFK-1)

What activates PFK-1?

ADP, AMP, Fructose-1,6-bisphosphate

What inhibits PFK-1?

ATP, Citrate, low pH

Why does ATP inhibit PFK-1?

High ATP indicates the cell already has enough energy

Why does AMP activate PFK-1?

High AMP indicates low energy availability

What enzyme catalyzes step 4?

Fructose-1,6-bisphosphate Aldolase

What enzyme class is Aldolase?

Lyase

What does Aldolase do?

Cleaves the 6-carbon sugar into two 3-carbon sugars: DHAP and GAP

What type of reaction occurs in step 4?

Cleavage

What enzyme catalyzes step 5?

Triose phosphate isomerase

What does Triose phosphate isomerase do?

Converts DHAP into GAP so it can continue through the rest of the pathway

What reaction occurs in step 5?

DHAP → G3P

After step 5, how many G3P molecules enter the payoff phase?

Two

What steps are the energy investment phase?

Steps 1-5

What steps are the energy payoff phase?

Steps 6-10

How many ATP are produced in the payoff phase?

4 ATP

Which steps covert ATP to ADP? (remove phosphate)

Steps 1 and 3

What enzyme catalyzes step 6?

Glyceraldehyde-3-phosphate Dehydrogenase

What enzyme class is Glyceraldehyde-3-phosphate Dehydrogenase?

Oxidoreductase

What does Glyceraldehyde-3-phosphate Dehydrogenase do?

Transfers electrons (oxidizes GAP) and adds an inorganic phosphate to create 1,3-bisphosphoglycerate

What reaction occurs in step 6?

G3P → 1,3-bisphosphoglycerate

What cofactor is used in Step 6?

NAD+

Which step produces NADH?

Step 6

What gets oxidized in step 6?

G3P

What gets reduced in step 6?

NAD+

What enzyme catalyzes step 7?

Phosphoglycerate Kinase

What reaction occurs in step 7?

1,3-BPG → 3-phosphoglycerate

What enzyme class is Phosphoglycerate Kinase?

Transferase

What does Phosphoglycerate Kinase do?

Transfers a phosphate group from 1,3-bisphosphoglycerate to ADP, forming ATP

What important process occurs in step 7?

Substrate level phosphorylation

How many ATP are produced in step 7?

2 ATP (1 per G3P)

Which reversible step produces ATP?

Step 7

What enzyme catalyzes step 8?

Phosphoglycerate mutase

What enzyme class is Phosphoglycerate mutase?

Isomerase

What does Phosphoglycerate mutase do?

Shifts the phosphate group from the 3rd to the 2nd carbon

What reaction occurs in Step 8?

3-phosphoglycerate → 2-phosphoglycerate

What enzyme catalyzes step 9?

Enolase

What enzyme class is Enolase?

Lyase

What does Enolase do?

Removes a molecule of water from 2-phosphoglycerate, creating PEP

What reaction occurs in Step 9?

2-phosphoglycerate → phosphoenolpyruvate (PEP)

What is removed during step 9?

Water

Which step removes water?

Step 9

What enzyme catalyzes step 10?

Pyruvate kinase

What enzyme class is Pyruvate kinase?

Transferase

What does Pyruvate kinase do?

Transfers a phosphate group from PEP to ADP, generating ATP and pyruvate

What reaction occurs in step 10?

PEP → Pyruvate

Which irreversible step produces ATP?

Step 10

Which steps produce ATP?

Steps 7 (reversible) and Step 10 (irreversible)

Which glycolysis steps use substrate-level phosphorylation?

Steps 7 & 10

What happens to pyruvate under aerobic conditions?

Converted into acetyl-CoA and enters the citric acid cycle

What happens to pyruvate under anaerobic conditions?

Converted into lactate