Understanding Glycolysis and the Krebs Cycle

Glycolysis Overview

• Glucose Breakdown:

  • Begins with a 6-carbon glucose molecule.
  • Glycolysis splits glucose into 2 pyruvate (pyruvic acid) molecules, each having 3 carbons.
  • This process is anaerobic (doesn't require oxygen).

• Energy Yield:

  • Net gain of 2 ATP (used 2 ATPs, generated 4 ATPs).
  • Produces 2 NADH molecules.

• Location:

  • Occurs in the cytoplasm of the cell.

Cellular Structures

• Eukaryotic Cell Components:

  • Outer membrane and nucleus.
  • Mitochondria as "power centers".

• Mitochondria Structure:

  • Outer and inner membrane.
  • Inner space known as the matrix.
  • Cristae: folds of the inner membrane.

Krebs Cycle (Citric Acid Cycle)

• Preparation for Krebs Cycle:

  • Pyruvate oxidation converts pyruvate into a 2-carbon compound called acetyl-CoA.
  • Produces NADH and CO2 as by-products.

• Process:

  • Acetyl-CoA merges with oxaloacetic acid (4-carbon) to form citrate (citric acid, 6-carbon).
  • Citrate undergoes oxidation, regenerating oxaloacetic acid.
  • During oxidation, 2 carbons are cleaved off as CO2.

• Energy and Electron Carriers:

  • Produces NADH, FADH2, and ATP.
  • NADH and FADH2 vital for the electron transport chain.

The Electron Transport Chain

• Role of NADH and FADH2:

  • NADH produces 3 ATPs each.
  • FADH2 produces 2 ATPs each.

• Total ATP Yield:

  • Glycolysis: 4 ATPs (net 2 from glycolysis + 2 from Krebs cycle).
  • Electron Transport Chain: 34 ATPs.
  • Potential total of 38 ATPs per glucose molecule.

Metabolism Beyond Glucose

• Alternative Catabolism:
  • Fats and proteins can be catabolized into acetyl-CoA.
  • Krebs cycle is the entry point for these catabolic pathways.

Key Takeaways

• Glycolysis and Krebs cycle are essential biochemical pathways in cellular respiration.
• Important to understand the transformation of glucose and the role of various intermediate molecules and processes.
• ATP is the main energy currency, with NADH and FADH2 contributing significantly through the electron transport chain.

Visual Aids

• Diagrams: Helpful to reference for detailed molecular structures and enzyme-catalyzed reactions.

Concluding Thoughts

• The lecture simplifies complex processes, highlighting the importance of these biochemical pathways in energy production.
• Understanding core processes like glycolysis and the Krebs cycle is crucial for broader insights into cellular metabolism and energy conversion.