Glycolysis HVYDVCB (1).pptx

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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.

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

5. 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.

6. Step 4: Cleavage Fructose-1,6-biphosphate is cleaved into two 3-carbon molecules by the enzyme Aldolase , dihydroxyacetonephosphate and glyceraldehyde-3-phosphate. 1 1

7. 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

8. 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.

9. 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 .

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

11. 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

12. 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.