Chem Chapter 24 Final - Glycolysis, Fate of Pyruvate and ATP Production

Glycolysis

The first step of glucose metabolism, breaking glucose into pyruvate

Where does glycolysis occur?

Occurs in the cytoplasm

How many enzymes are involved in glycolysis?

10 enzymes

Step 1 of Glycolysis

Phosphorylation of Glucose

Reactants in step 1 of glycolysis

Glucose + ATP

Enzyme used in step 1 of glycolysis

Hexokinase

Products in step 1 of glycolysis

Glucose-6-phosphate (G6P) + ADP

Process of step 1 of glycolysis

ATP donates a phosphate group to glucose, forming glucose-6-phosphate

Step 2 of glycolysis

Isomerization of Glucose-6-Phosphate

Reactants in step 2 of glycolysis

Glucose-6-phosphate (G6P)

Enzyme used in step 2 of glycolysis

Phosphoglucoisomerase

Products in step 2 of glycolysis

Fructose-6-phosphate (F6P)

Process of step 3 in glycolysis

G6P is rearranged to form F6P (same molecular formula, different structure)

Step 3 of glycolysis

Phosphorylation of Fructose-6-Phosphate

Enzyme in step 3 of glycolysis

Phosphofructokinase (PFK)

Reactants in step 3 of glycolysis

Fructose-6-phosphate (F6P) + ATP

Products in step 3 of glycolysis

Fructose-1,6-bisphosphate (F1,6BP) + ADP

Process of step 3 of glycolysis

ATP adds a second phosphate group to F6P, producing F1,6BP

What step is the rate-limiting step in glycolysis?

Step 3 - Phosphorylation of Fructose-6-Phosphate

Step 4 of glycolysis

Cleavage of Fructose-1,6-bisphosphate

Reactant in step 4 of glycolysis

Fructose-1,6-bisphosphate (F1,6BP)

Enzyme in step 4 of glycolysis

Aldolase

Products in step 4 of glycolysis

Glyceraldehyde-3-phosphate (G3P)

Dihydroxyacetone phosphate (DHAP)

Process of step 4 in glycolysis

The 6-carbon fructose-1,6-bisphosphate is split into two 3-carbon molecules: G3P and DHAP

What kind of group does G3P have?

Aldehyde group

What kind of group does DHAP have?

Ketone group

Step 5 of glycolysis

Isomerization of DHAP to G3P

Reactant in step 5 of glycolysis

Dihydroxyacetone phosphate (DHAP)

Enzyme used in step 5 of glycolysis

Triose Phosphate Isomerase

Product in step 5 of glycolysis

Glyceraldehyde-3-phosphate (G3P)

Process of step 5 of glycolysis

DHAP is converted into another molecule of G3P

Now, there are two molecules of G3P

why are there two molecules of G3P after step 5?

Since glycolysis is proceeding in parallel for each molecule of glucose

Step 6 of glycolysis

Oxidation and Phosphorylation of G3P

Enzyme used in step 6 of glycolysis

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH)

Reactants in step 6 of glycolysis

Glyceraldehyde-3-phosphate (G3P)

NAD⁺ (Nicotinamide adenine dinucleotide)

Inorganic phosphate (Pi)

Products in step 6 of glycolysis

NADH (Nicotinamide adenine dinucleotide, reduced)

1,3-Bisphosphoglycerate (1,3-BPG)

Process of step 6 in glycolysis

G3P is oxidized (loses electrons) and phosphorylated

NAD⁺ is reduced to NADH, and an inorganic phosphate is added to the molecule

1,3-BPG is formed, which is a high-energy intermediate

When are 2 ATPs used?

2 ATPs used in the first two phosphorylation steps (Step 1 and Step 3)

No ATP has been produced

How many NADH is produced in step 6?

2 NADH; used later for the ETC to produce ATP

Step 7 of glycolysis

Substrate-Level Phosphorylation

Reactants in step 7 of glycolysis

1,3-Bisphosphoglycerate (1,3-BPG)

ADP

Enzyme used in step 7 of glycolysis

Phosphoglycerate kinase

Products in step 7 of glycolysis

ATP (via substrate-level phosphorylation)

3-Phosphoglycerate (3PG)

What step is the first ATP production in glycolysis?

Step 7

Process of step 7 in glycolysis

1,3-BPG transfers a phosphate to ADP, forming ATP and producing 3-phosphoglycerate

How many net ATP after step 7 of glycolysis?

Net ATP so far: 0 ATP (2 ATPs were used initially, and 2 ATPs are produced here, so we break even)

Step 8 of glycolysis

Isomerization of 3-Phosphoglycerate

Enzyme used in step 8 of glycolysis

Phosphoglycerate mutase

Reactant used in step 8 of glycolysis

3-Phosphoglycerate (3PG)

Products in step 8 of glycolysis

2-Phosphoglycerate (2PG)

Process of step 8 in glycolysis

A phosphate group is moved from carbon 3 to carbon 2, creating 2-phosphoglycerate

What kind of reaction is step 8 in glycolysis?

isomerization

Step 9 of glycolysis

Dehydration of 2-Phosphoglycerate

Enzyme used in step 9 of glycolysis

Enolase

Reactant in step 9 of glycolysis

2-Phosphoglycerate (2PG)

Product in step 9 of glycolysis

Phosphoenolpyruvate (PEP) + Water (H₂O)

Process of step 9 in glycolysis

A water molecule is removed from 2-phosphoglycerate

This results in the formation of phosphoenolpyruvate (PEP), a high-energy intermediate

Step 10 of glycolysis

Substrate-Level Phosphorylation (Final ATP Production)

Enzyme used in step 10 of glycolysis

Pyruvate kinase

Reactants in step 10 of glycolysis

Phosphoenolpyruvate (PEP)

ADP

Products in step 10 of glycolysis

ATP (via substrate-level phosphorylation)

Pyruvate

Process of step 0 of glycolysis

PEP transfers a phosphate group to ADP, forming ATP and producing pyruvate

Which step is the second ATP production in glycolysis?

Step 10

Net ATP after step 10 of glycolysis

2 ATP

(2 ATPs were used initially, and 4 ATPs are produced, but the net total is 2 ATP because the first 2 ATPs were consumed in earlier reactions)

Final Products from Glycolysis:

Pyruvate

2 pyruvate molecules

Final Products from Glycolysis:

ATP

2 ATP (net)

4 ATPs produced in total, but 2 were used in the first steps

Final Products from Glycolysis:

NADH

2 NADH

What does the fate of pyruvate depend on?

Whether oxygen is available

Pyruvate in aerobic conditions

Pyruvate is converted into acetyl-CoA in the mitochondria.

Acetyl-CoA enters the Krebs cycle, where it helps produce more ATP and NADH

Pyruvate in anaerobic conditions

In muscles (during intense activity), pyruvate is converted into lactate (lactic acid), causing muscle fatigue

In yeast and plants, pyruvate is converted into ethanol and CO₂ (alcohol fermentation), which is important for processes like brewing and baking

Pyruvate with oxygen (aerobic) in short

Pyruvate → Acetyl-CoA → Krebs cycle (more ATP)

Pyruvate without oxygen (anaerobic) in short

Pyruvate → Lactate (muscles) or Ethanol + CO₂ (yeast/plants)