Cellular Respiration

• Cellular respiration


  A crucial metabolic process where organic molecules are broken down to release energy for cell activities
• Cellular respiration occurs in every cell in the body to provide energy
• Cellular respiration


  1. Series of more than 20 separate reactions

  2. Each catalyzed by a different enzyme

  3. Energy release is controlled throughout this process to avoid sudden energy release
• Cellular Respiration Equation: glucose + oxygen —> water + carbon dioxide +energy
• 6C6H12O6 + 6O2 —> 6H2O + 6CO2+ Energy
• Energy use by the cell

  Cells utilize ATP for various processes
• Only 40% of energy from respiration is incorporated into ATP
• 60% of energy is lost as heat
• ATP


  Used in anabolic reactions to build large molecules
• Catabolic reactions


  Release energy
• Anabolic reactions


  Require energy
• Cellular Respiration


  1. Glycolysis

  2. Krebs Cycle

  3. Electron Transport System
• Glycolysis


  'splitting glucose'
• Glycolysis


  • Anaerobic
  • Occurs in the cytosol (cytoplasm)
  • Glucose is only partially broken down
  • Breaks down one molecule of glucose (C6H12O6)
  • Produces two molecules of pyruvate (pyruvic acid – C3H4O3)
• Glycolysis


  Pyruvate can either be converted into lactic acid or broken further aerobically (with oxygen) to release more energy
• Krebs Cycle


  1. Pyruvate is converted to acetyl coenzyme A (acetly CoA)

  2. Two molecules of acetyl CoA then enter the citric acid cycle (or Krebs Cycle)

  3. The Krebs cycle (citric acid cycle) produces 2 ATP molecules from the 2 molecules of acetyl CoA
• Electron Transport System


  1. Final stage of cellular respiration

  2. Only stage that uses oxygen

  3. Electrons are passed between molecules, finally resulting in oxygen molecules forming water

  4. The two molecules of Acetyl CoA have the ability to produce 34 molecules of ATP (theoretical maximum)
• Anaerobic Respiration


  Process that produces ATP in the absence of oxygen
• Anaerobic Respiration


  • Location: Cytosol
  • Glucose is used to produce TWO ATP molecules
  • Glycolysis breaks down glucose into pyruvic acid without oxygen
  • Pyruvic acid converted to lactic acid in anaerobic conditions
  • Produces ATP in the absence of oxygen
  • Important during vigorous activity when oxygen supply is insufficient
  • Lactic acid may accumulate, causing muscle pain
  • Lactic acid transported to the liver, converted back to glucose
• Aerobic Respiration


  Complete glucose breakdown requires oxygen
• Aerobic Respiration


  • Mitochondria are the sites of aerobic respiration in cells
  • Pyruvate is converted to acetyl coenzyme A- when CO2 Molecule is removed from pyruvate and remaining two carbon structures join