Understanding the Simplified Krebs Cycle

Aug 8, 2024

Mindmap

Lecture Notes: Simplifying the Krebs Cycle

Introduction

  • Goal: Best way to remember the Krebs cycle (Citric Acid Cycle).
  • Challenges: Many intermediates, enzymes, reactions, and CO2 movements.
  • Approach: Easy ways to remember intermediates, carbon counts, energy changes, and enzymes.
  • Prerequisite: Watch the detailed explanation video on Krebs cycle.

Key Molecules of Krebs Cycle

  • Total: 8 key molecules.
  • Mnemonic: "Can I keep selling substances for money, officer?"
    • C: Citrate
    • I: Isocitrate
    • K: alpha-Ketoglutarate
    • S: Succinyl-CoA
    • S: Succinate
    • F: Fumarate
    • M: Malate
    • O: Oxaloacetate
  • Tip: Succinate always follows Succinyl-CoA.

Carbon Counts and Energy Changes

  • Starting Point: Acetyl CoA (2 carbon) + Oxaloacetate (4 carbon) = Citrate (6 carbon).
  • Carbon Count Process:
    • Citrate: 6 carbons (no change in rearrangement)
    • Isocitrate: 6 carbons
    • alpha-Ketoglutarate: 5 carbons (1 CO2 removed)
    • Succinyl-CoA: 4 carbons (1 CO2 removed)
    • Succinate, Fumarate, Malate, Oxaloacetate: Remain 4 carbons
  • Energy Extraction:
    • Forms: Hydrogen ions stored in FAD and NAD
    • Energy Shuttles: NADH and FADH2
    • Production:
      • NADH at carbon drops and malate to oxaloacetate conversion
      • FADH2 during succinate to fumarate conversion
      • Dehydrogenase enzymes facilitate these steps

Enzymes of Krebs Cycle

  • Mnemonic: "At disco, devils sip down 5 drinks"
    • S: Synthases
    • D: Dehydrogenases
  • Key Enzymes:
    • Citrate Synthase: Acetyl-CoA + Oxaloacetate -> Citrate
    • Aconitase: Citrate -> Isocitrate
    • Isocitrate Dehydrogenase: Isocitrate -> alpha-Ketoglutarate
    • alpha-Ketoglutarate Dehydrogenase: alpha-Ketoglutarate -> Succinyl-CoA
    • Succinyl-CoA Synthase: Succinyl-CoA -> Succinate
    • Succinate Dehydrogenase: Succinate -> Fumarate
    • Fumarase: Fumarate -> Malate
    • Malate Dehydrogenase: Malate -> Oxaloacetate

Summary

  • Recommendations: Subscribe on YouTube, like on Facebook for flashcards.
  • Purpose: Simplify and retain Krebs cycle information for years.

Note: For complete understanding, refer to the detailed explanation of the Krebs cycle and related energy pathways like the Electron Transport Chain.