Introduction to Cellular Respiration

Introduction to Cellular Respiration

• Cellular respiration is a vital metabolic process in living organisms, breaking down glucose to release energy.
• While elegant and fascinating, it's also a complex process.
• The process involves three major steps: glycolysis, the Krebs cycle, and oxidative phosphorylation.
• Understanding these steps helps grasp how organisms use glucose for energy.

Cellular Respiration: The Process

• Cellular respiration is the process by which living cells break down glucose molecules to release energy.
• ATP (adenosine triphosphate) is a key molecule produced during this process.

Three Stages of Cellular Respiration

• Glycolysis:
  • Glucose, a six-carbon sugar, undergoes chemical transformations in the cytoplasm.
  • It's converted to two molecules of pyruvate, three-carbon organic molecules.
  • ATP is produced, and NAD+ is converted to NADH during glycolysis.
• Pyruvate Oxidation:
  • Pyruvate from glycolysis enters the mitochondrial matrix.
  • It's transformed into a two-carbon molecule (acetyl CoA) bound to coenzyme A.
  • Carbon dioxide is released, and NAD+ is reduced to NADH.
• Krebs Cycle (Citric Acid Cycle):
  • Acetyl CoA combines with a four-carbon molecule in a cyclical series of reactions, regenerating the four-carbon molecule.
  • ATP, NADH, and FADH2 are produced.
  • Carbon dioxide is released as a byproduct.
• Oxidative Phosphorylation:
  • NADH and FADH2 from previous steps deposit their electrons in the electron transport chain.
  • Electrons move, releasing energy to pump protons (H+) out of the matrix.
  • A proton gradient is formed which drives ATP synthases.
  • Oxygen accepts electrons at the end of the chain to form water.

ATP Production Tally

• Glycolysis: 2 ATP
• Krebs Cycle: 2 ATP
• Oxidative Phosphorylation: 34 ATP
• Overall: Approximately 38 ATP per glucose molecule.