Overview of Cellular Respiration

Introduction

• Cellular respiration is a complex process used by cells to convert glucose into ATP.
• We'll follow the traditional narrative focusing on glucose conversion through glycolysis, Krebs cycle, and oxidative phosphorylation.

Glycolysis

• Occurs in the cytosol of the cell.
• Splits a 6-carbon glucose molecule into two 3-carbon molecules called pyruvate.
• Net Production:
  • 2 ATPs (produces 4 ATPs, uses 2 ATPs)
  • 2 NADH (NAD+ is reduced to NADH)
• Decision Point:
  • Fermentation (anaerobic): Converts pyruvate into waste products, oxidizing NADH back to NAD+.
  • Aerobic Respiration: Continues with cellular respiration using oxygen.

Conversion of Pyruvate

• Pyruvate is decarboxylated, releasing CO2.
• The remaining acetyl group forms acetyl CoA by bonding with coenzyme A.
• This step also produces NADH from NAD+.
• Occurs twice per glucose molecule, producing 2 NADH.

Krebs Cycle (Citric Acid Cycle)

• Occurs in the mitochondrial matrix.
• Acetyl CoA transfers acetyl group to oxaloacetic acid, forming citric acid.
• Citric acid (6-carbon) undergoes breakdown back to oxaloacetic acid (4-carbon).
• Products per glucose:
  • 6 NADH
  • 2 FADH2 (converted to QH2)
  • 2 ATP/GTP
  • CO2 released

Oxidative Phosphorylation

• Utilizes NADH and QH2 to create a proton gradient across the inner mitochondrial membrane (cristae).
• ATP Yield (approximate values):
  • Each NADH: 2-3 ATPs
  • Each QH2: 1.5-2 ATPs
• Total ATP from Electron Transport:
  • 27-38 ATPs possible.
  • Observed in cells: around 29-30 ATPs
• Efficiency varies by cell type and condition.

Location of Processes

• Glycolysis: Cytosol
• Krebs Cycle: Mitochondrial matrix
• Electron Transport Chain: Across the inner membrane of the mitochondrial cristae

Summary

• Cellular respiration efficiently produces ATP using glucose.
• It involves interconnected biochemical pathways with various enzymes and coenzymes facilitating the process.
• Future discussions will detail each component further, particularly electron transport and mitochondria structure.