Glycolysis, also known as the Embden-Meyerhoff pathway, is a metabolic process occurring in the cytoplasm that converts glucose into two pyruvate molecules, utilizing ATP without the need for oxygen. The pathway involves ten steps facilitated by specific enzymes, resulting in the net production of 2 ATP, 2 NADH, and 2 pyruvate, with potential conversion to lactate if oxidization is impaired. Each step, including phosphorylation, isomerization, and substrate-level phosphorylation, is critical for energy production and metabolic regulation.

1. Glycolysis
Presentation by :
Mpho Langalanga
Natasha Dumbu
Tawanda Chikwenengere

2. Introduction
• Glycolysis is also called Embden-Meyerhoff pathway
• Glycolysis is a metabolic pathway that occurs in the cytoplasm of cells
and is the first step in the process of cellular respiration.
• It is a series of biochemical reactions that convert glucose, a six
carbon sugar into two molecules of pyruvate, a 3 carbon molecule.
• It occurs without molecular oxygen and it uses energy in the form of
ATP.

3. Step 1 : Glucose Phosphorylation
• Glucose is phosphorylated by enzyme Hexokinase, which uses 1 ATP
molecule to add phosphate group to glucose forming Glucose 6
phosphate.
• This makes it more chemically reactive.
• The charge on the phosphate also traps the sugar (glucose) in the cell,
this reaction is irreversible.

5. Step 2: Isomerization
• Glucose 6 phosphate is converted to Fructose 6 phosphate, by
enzyme phosphoglucoisomerase.
• This reaction is readily reversible.

6. Step 3: Second Phosphorylation
• Fructose 6 phosphate is phosphorylated by the enzyme
phosphofructokinase-1, using 1 ATP molecule forming Fructose 1,6-
biphosphate.
• Phosphofructokinase is a allosteric enzyme and also a major
regulatory enzyme
• The reaction is irreversible.

7. Step 4: Cleavage
• Fructose-1,6-biphosphate is cleaved into two 3-carbon molecules by the enzyme Aldolase , dihydroxyacetonephosphate and glyceraldehyde-3-phosphate.
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8. Step 5: Isomerization
• Dihydroxyacetone phosphate is converted to Glyceraldehyde-3-
phosphate by the triosephosphate isomerase.
• This reaction never reaches equilibrium, G3P is used in the next step
as fast as it forms

9. Step 6: Oxidation and Phosphorylation
• Glyceraldehyde-3-phosphate is oxidised by the enzyme, Triose
phosphate dehydrogenase producing NADH and a high energy
intermediate molecule , 1,3 biphosphoglycerate.
• The energy released is used to phosphorylated ADP to ATP, producing
1 ATP molecule.

10. Step 7: substrate level phosphorylation
• This is the first step of energy production
• A phosphate group is transferred from 1,3-biphosphoglycerate to ADP
forming ATP and 3 phosphoglycerate, catalysed by the enzyme
phosphoglycerokinase.

11. Step 8: Isomerization
• 3-phosphoglycerate is isomerised to 2-phosphoglycerate by the
enzyme phosphoglyceromutase.

12. Step 9: Dehydration
• 2 phosphoglycerate loses a water molecule, forming
phosphoenolpyruvate(PEP), catalysed by the enzyme enolase.
• PEP is a compound with very high potential energy

13. STEP 10: Final substrate level phosphorylation
• PEP transfers its high energy group to ADP, forming ATP and pyruvate,
catalysed by the enzyme pyruvate kinase.
• Glycolysis results in the net production of 2 ATP molecule, 2 NADH
and 2 pyruvate.
• When pyruvate cannot be oxidised within mitochondria for some
reason, pyruvate is reduced to lactate by lactate dehydrogenase. This
usually happens during anaerobic respiration.