Respiration

• External respiration


  The process by which organisms exchange gases with their environment
• Internal respiration


  The controlled release of energy from food
• Aerobic respiration


  The controlled release of energy from food using oxygen
• Aerobes


  • Organisms that carry out aerobic respiration
• Aerobic respiration


  1. Glucose

  2. Oxygen

  3. Carbon dioxide

  4. Water

  5. Energy (ATP)
• Aerobic respiration is very efficient with 40% of the glucose being converted into energy. The energy not converted to ATP is lost as heat.
• Glycolysis (Stage 1)


  1. Breakdown of glucose to two 3 carbon molecules (pyruvic acid)

  2. Takes place in the cytosol (cytoplasm) of the cell

  3. ATP is produced from the small amount of energy released in this reaction

  4. Yields low energy

  5. End products: 2 NADH, 2 ATP + water, 2 pyruvic acid
• Krebs Cycle and Electron Transport System (Stage 2)


  1. Requires oxygen

  2. Occurs in the mitochondria where enzymes are present to control reactions

  3. Pyruvic acid is broken down further to CO2, water and energy

  4. High energy is yielded and used to create more ATP

  5. CO2 and water are the end products

  6. Acetyl coenzyme A is converted into carbon dioxide and hydrogen

  7. High energy protons and electrons (H+) are released to form NADHS

  8. ADP is converted to ATP
• Respiration

  1. Glucose

  2. 2 ADP + 2P

  3. NAD+

  4. 2e

  5. Stage 1: Glycolysis (2 ATP + water, 2 Pyruvic acid (C3), NADH to electron transport system)

  6. Stage 2: Krebs cycle (Acetyl coenzyme A (C2), NADH to electron transport system, 2e, CO2, ATP)

  7. Electron Transport System (NADH releases high-energy electrons, passed from molecule to molecule, energy used to form ATP, low-energy electrons combine with oxygen and hydrogen to form water)
• Anaerobic respiration

  Controlled release of energy from food without the use of oxygen
• Anaerobic respiration does not make any extra energy
• Types of anaerobic respiration (fermentation) in microorganisms


  • Lactic acid fermentation
  • Alcohol fermentation
• Anaerobic respiration only consists of one stage where glucose is converted to pyruvic acid
• Anaerobic Respiration

  1. NADH releases electrons and protons

  2. Combine with pyruvic acid

  3. Form lactic acid or ethanol and CO2

  4. ATP and NADH are the end products
• Glycolysis

  1. Glucose (C6)

  2. 2 ADP + 2P

  3. 2 Pyruvic acid (C3)

  4. 2 ATP + water
• Lactic acid fermentation

  1. In absence of oxygen

  2. Some bacteria

  3. Human muscle

  4. 2 Lactic acid
• Alcohol fermentation


  1. Yeast

  2. Plant cells

  3. 2 Ethanol

  4. 2 Carbon dioxide
• Alcohol is made when yeast cells are deprived of oxygen and fed sugar
• Alcohol fermentation occurs as a result of the partial breakdown of glucose to form alcohol and carbon dioxide
• Apparatus

  • Dried yeast
  • Glucose
  • Oil
  • Boiled water
  • Delivery tube
  • Potassium iodine
  • Sodium Hypochlorite
  • Beakers
  • Test tube
  • Bunsen burner
  • Water bath
• Method (a)

  1. Add yeast and boiled glucose to a flask

  2. Attach stopper and tube

  3. Place in water bath

  4. Place tubing into limewater

  5. Bubbles of CO2 will be seen in the limewater
• Method (b)

  1. Filter the yeast solutions

  2. Place in test tubes

  3. Add potassium iodine

  4. Add sodium hypochlorite

  5. Place in water bath over Bunsen burner
• Alcohol will be present in the test tube