The Surprising Truth About Glycolysis Pathway Nobody Tells You

What is the overall net energy yield of Glycolysis? Considering both phases, the net energy gain from glycolysis is calculated as follows: ATP Consumption: 2 ATP molecules (in the investment phase) ATP Production: 4 ATP molecules (in the generation phase) NADH Production: 2 NADH molecules (in the generation phase) Therefore, the net gain of ATP directly from glycolysis is 2 ATP molecules. The 2 NADH molecules produced are also crucial for energy. Each NADH molecule can be further processed in the electron transport chain (under aerobic conditions) to generate approximately 2.5 ATP molecules. So, the 2 NADH can yield an additional 5 ATP molecules. This means the total theoretical net ATP generated from glycolysis is 7 ATP molecules (2 direct ATP + 5 ATP from NADH). What are some key enzymes and molecules involved in the 10-step glycolysis pathway? The glycolysis pathway involves ten distinct steps, each catalysed by a specific enzyme: Energy Investment Phase (Steps 1-5): Glucose → Glucose-6-phosphate: Catalysed by Hexokinase (or Glucokinase in liver). Requires ATP. (Irreversible) Glucose-6-phosphate → Fructose-6-phosphate: Catalysed by Phosphoglucoisomerase (or Phosphohexoisomerase). (Reversible) Fructose-6-phosphate → Fructose-1,6-bisphosphate: Catalyzed by Phosphofructokinase-1 (PFK-1). Requires ATP. (Irreversible, major regulatory step) Fructose-1,6-bisphosphate → Dihydroxyacetone phosphate (DHAP) + Glyceraldehyde-3-phosphate (G3P): Catalysed by Aldolase. (Reversible) Dihydroxyacetone phosphate → Glyceraldehyde-3-phosphate: Catalysed by Triose phosphate isomerase. (Reversible) Energy Generation Phase (Steps 6-10) (occurs twice per glucose molecule): Glyceraldehyde-3-phosphate → 1,3-Bisphosphoglycerate: Catalyzed by Glyceraldehyde-3-phosphate dehydrogenase. Produces NADH and incorporates an inorganic phosphate. (Reversible) 1,3-Bisphosphoglycerate → 3-Phosphoglycerate: Catalysed by Phosphoglycerate kinase. Produces ATP (first substrate-level phosphorylation). (Reversible) 3-Phosphoglycerate → 2-Phosphoglycerate: Catalysed by Phosphoglycerate mutase. (Reversible) 2-Phosphoglycerate → Phosphoenolpyruvate (PEP): Catalysed by Enolase. Releases water. (Reversible) Phosphoenolpyruvate → Pyruvate: Catalysed by Pyruvate kinase. Produces ATP (second substrate-level phosphorylation). (Irreversible, regulatory step) Key Molecules: Glucose: Starting substrate. ATP/ADP: Energy currency, consumed in the investment phase and produced in the generation phase. NAD+/NADH: Electron carrier, NAD+ is reduced to NADH in step 6, carrying electrons for later ATP production in the electron transport chain. Inorganic Phosphate (Pi): Utilised in step 6 for phosphorylation. Pyruvate: End product of glycolysis, with various fates depending on oxygen availability. Glucose (C6H12O6): The initial six-carbon sugar molecule that is broken down in glycolysis to produce energy. Major sugar in the blood is used by various tissues. Glucose 6-phosphate: The phosphorylated form of glucose, trapped inside the cell after the first step of glycolysis. Fructose 6-phosphate: An isomer of Glucose 6-phosphate, a key intermediate in the pathway. Fructose 1,6-bisphosphate: A six-carbon sugar with phosphate groups at both the 1st and 6th carbons. Its instability leads to its splitting into two three-carbon molecules. Dihydroxyacetone Phosphate (DHAP): A three-carbon molecule produced from the splitting of Fructose 1,6-bisphosphate; readily isomerised to Glyceraldehyde 3-phosphate. Glyceraldehyde 3-phosphate (G3P): A three-carbon molecule, and the only direct product from the splitting of Fructose 1,6-bisphosphate that can continue down the glycolytic pathway. All subsequent steps effectively occur twice for each initial glucose molecule. 1,3-Bisphosphoglycerate: A high-energy three-carbon intermediate, crucial for the first substrate-level phosphorylation to produce ATP. 3-Phosphoglycerate: A three-carbon molecule, product of the first ATP-generating step. 2-Phosphoglycerate: An isomer of 3-Phosphoglycerate, with the phosphate group shifted. Phosphoenolpyruvate (PEP): A very high-energy three-carbon molecule, crucial for the second substrate-level phosphorylation to produce ATP. Pyruvate: The final three-carbon product of glycolysis (two molecules per glucose). Its fate depends on the presence or absence of oxygen. ATP (Adenosine Triphosphate): The primary energy currency of the cell. Consumed in the initial steps and produced in later steps of glycolysis. ADP (Adenosine Diphosphate): Converted to ATP by gaining a phosphate group. NAD+ (Nicotinamide Adenine Dinucleotide): An electron acceptor that is reduced to NADH during glycolysis. NADH: A reduced electron carrier that transports electrons to the electron transport chain for further ATP production in aerobic conditions, or is re-oxidised to NAD+ in anaerobic conditions. Lactate: The end-product of anaerobic glycolysis, formed from pyruvate to regenerate NAD+