Glycolysis Steps: A Detailed Explanation

📚 What is Glycolysis?

Glycolysis is the metabolic pathway that converts glucose ($C_6H_{12}O_6$) into pyruvate ($CH_3COCOO^−$ + $H^+$). It's a fundamental process in cells that produces energy in the form of ATP and NADH.

🧪 Objectives

• 🎯 Understand the 10 steps of glycolysis.
• 🔬 Identify the enzymes involved in each step.
• 💡 Explain the energy investment and payoff phases.

⚗️ Materials

• 🧬 Diagrams of the glycolysis pathway
• 🧪 Models of glucose and related molecules
• 💻 Computer with internet access for research

🔥 Warm-up (5 mins)

Quick review of basic carbohydrate structures and enzyme functions.

👨‍🏫 Main Instruction

Let's dive into each of the 10 steps of glycolysis:

1. ✨ Step 1: Hexokinase

   • Reaction: Glucose is phosphorylated to glucose-6-phosphate.

   • Enzyme: Hexokinase

   • Significance: Traps glucose inside the cell and commits it to glycolysis.

2. 🔄 Step 2: Phosphoglucose Isomerase

   • Reaction: Glucose-6-phosphate is isomerized to fructose-6-phosphate.

   • Enzyme: Phosphoglucose Isomerase

   • Significance: Converts glucose-6-phosphate to a form that can be easily phosphorylated in the next step.

3. 💰 Step 3: Phosphofructokinase-1

   • Reaction: Fructose-6-phosphate is phosphorylated to fructose-1,6-bisphosphate.

   • Enzyme: Phosphofructokinase-1 (PFK-1)

   • Significance: A key regulatory step; PFK-1 is allosterically regulated.

4. ✂️ Step 4: Aldolase

   • Reaction: Fructose-1,6-bisphosphate is cleaved into glyceraldehyde-3-phosphate (GAP) and dihydroxyacetone phosphate (DHAP).

   • Enzyme: Aldolase

   • Significance: Creates two 3-carbon molecules from one 6-carbon molecule.

5. ↔️ Step 5: Triose Phosphate Isomerase

   • Reaction: Dihydroxyacetone phosphate (DHAP) is converted to glyceraldehyde-3-phosphate (GAP).

   • Enzyme: Triose Phosphate Isomerase

   • Significance: Ensures that all molecules proceed through the second half of glycolysis.

6. ⚡ Step 6: Glyceraldehyde-3-Phosphate Dehydrogenase

   • Reaction: Glyceraldehyde-3-phosphate is phosphorylated and oxidized to 1,3-bisphosphoglycerate.

   • Enzyme: Glyceraldehyde-3-Phosphate Dehydrogenase

   • Significance: Generates NADH, an important electron carrier.

7. 💸 Step 7: Phosphoglycerate Kinase

   • Reaction: 1,3-bisphosphoglycerate transfers a phosphate group to ADP, forming ATP and 3-phosphoglycerate.

   • Enzyme: Phosphoglycerate Kinase

   • Significance: The first ATP-generating step in glycolysis.

8. 🔄 Step 8: Phosphoglycerate Mutase

   • Reaction: 3-phosphoglycerate is converted to 2-phosphoglycerate.

   • Enzyme: Phosphoglycerate Mutase

   • Significance: Prepares the molecule for the next ATP-generating step.

9. 💧 Step 9: Enolase

   • Reaction: 2-phosphoglycerate is dehydrated to phosphoenolpyruvate (PEP).

   • Enzyme: Enolase

   • Significance: Creates a high-energy phosphate compound.

10. ✅ Step 10: Pyruvate Kinase

    • Reaction: Phosphoenolpyruvate (PEP) transfers a phosphate group to ADP, forming ATP and pyruvate.

    • Enzyme: Pyruvate Kinase

    • Significance: The second ATP-generating step; pyruvate is the end product of glycolysis.

📝 Assessment

A short quiz to test understanding of the steps, enzymes, and significance of glycolysis.