Cellular Respiration

• C6H12O6 + 6O2 --> 6CO2 + H2O
• anaerobic respiration: occurs when there is an absence of oxygen.

  • glycolysis
  • Small yield of ATP from glucose
• Aerobic Respiration: occurs in the presence of oxygen to produce energy (36 ATP)
• Glycolysis: The first stage of cellular respiration that breaks down one molecule of glucose into two pyruvate molecules, producing a small amount of ATP.
• Anaerobic Respiration in animals:

  • Glucose becomes activated - 2 ATP --> 2ADP + 2P
  • Glucose splits into 2PGAL
  • 2PGAL becomes 2PGA -- 2NAD+ + 2H --> 2NADH, 2ADP + 2P --> 2ATP
  • PGA becomes pyruvic acid - 2ADP + 2P --> 2ATP. H2O is also released
  • Pyruvic acid is converted into lactic acid - NADH --> NAD+ + H+
• Yeast alcohol fermentation:

  1. glucose is activated - 2ATP --> 2ADP + 2P
  2. Glucose splits into 2PGAL
  3. 2PGAL becomes 2PGA - 2NAD + 2H -> 2NADH , 2ADP + 2P -> 2ATP
  4. PGA becomes pyruvate - 2ADP + 2P -> 2ATP . H2O is also released
  5. Pyruvic acid is converted into alcohol - pyruvic acid -> alcohol + CO2
• Aerobic Respiration: Requires O2 and completely oxidizes glucose to CO2, H2O, and 36 ATP
• Krebs Cycle (citric acid cycle):

  1. Acetyl CoA joins with oxaloacetic acid forming citric acid and goes through krebs cycle

  • 3 NAD + 3H --> 3NADH
  • FAD + 2H --> FADH2
  • ADP + P --> ATP
  • 2CO2 are released (decarboxylation)
• Link Reaction:

  1. Pyruvic acid is unstable in the presence of O2 and breaks down into acetic acid


  • decarboxylation of pyruvic acid, releasing CO2
  • NAD + H --> NADH

  1. Acetic acid attaches to co-enzyme A forming acetyl CoA
• Cytochrome Enzyme System: A series of enzymes that catalyze the oxidation of pyruvate to acetyl CoA by passing H ions and its electron from acceptor to acceptor.

  • ATP is formed by ATP synthase: 32 ADP + 32 P --> 32 ATP
• Oxygen is the final electron acceptor, without it electrons become backed up and aerobic respiration ceases. Oxygen combines with electrons and H+ to form water which is the final product