Chp - 11 Respiration

• Processes where energy is used


  • Muscle contraction
  • Cell division
  • Absorption of nutrients in the gut by active transport
  • Transmitting nerve impulses
  • Protein synthesis
  • Making new cell membranes and cell structures
  • Keeping the body temperature constant
• Aerobic respiration


  Glucose + Oxygen >> Carbon dioxide + water + energy released
• Anaerobic respiration


  Glucose -> lactic acid + energy released
• Aerobic respiration


  • Involves chemical reactions in cells that break down glucose to release energy
  • Uses oxygen
  • No alcohol or lactic acid made
  • Large amount of energy released from each molecule of glucose
  • Carbon dioxide made
• Anaerobic respiration

  • Involves chemical reactions in cells that break down glucose to release energy
  • Does not use oxygen
  • Alcohol (in yeast and plants) or lactic acid (in animals) is made
  • Much less energy released from each molecule of glucose
  • Carbon dioxide is made by yeast and plants, but not by animals
• Vigorous exercise


  Muscles start to carry out anaerobic respiration
• Anaerobic respiration in muscles


  Glucose is broken down to lactic acid instead of carbon dioxide and water
• Lactic acid builds up in muscles and blood


  Causes oxygen debt
• Oxygen debt removal


  1. Faster and deeper breathing to supply more oxygen

  2. Lactic acid broken down in the liver by aerobic respiration
• Oxygen debt


  Lactic acid needs to be broken down, requiring extra oxygen
• Control of breathing rate

  1. Brain monitors blood pH

  2. Detects high CO2 or lactic acid

  3. Sends nerve impulses to stimulate diaphragm and intercostal muscles to contract harder and more often
• Gas exchange surfaces


  • Permeable
  • One cell thick
  • Efficient transport system
  • Large surface area
  • Good oxygen supply
  • Moist
• Human breathing system


  1. Air enters mouth/nose

  2. Passes through throat, larynx, trachea

  3. Branches into bronchi, bronchioles, alveoli

  4. Gas exchange occurs in alveoli
• Trachea


  • Kept open by C-shaped rings of cartilage
  • Cartilage prevents trachea from collapsing
• Gas exchange at the alveolus


  1. Oxygen diffuses from alveolus into blood

  2. Oxygen combines with hemoglobin in red blood cells

  3. Carbon dioxide diffuses from blood into alveolus and is breathed out
• Respiratory passage lining


  • Goblet cells release mucus
  • Cilia sweep mucus containing bacteria and dust up to the throat
• Inspired air contains 21% oxygen, 0.04% carbon dioxide, variable water vapour
• Expired air contains 16% oxygen, 4% carbon dioxide, very high water vapour
• Inspiration (breathing in)

  1. External intercostal muscles contract, internal intercostal muscles relax, raising ribs

  2. Diaphragm contracts and flattens, pulling downwards

  3. Thoracic volume increases, pressure decreases, air moves into lungs
• Expiration (breathing out)


  1. Internal intercostal muscles contract, external intercostal muscles relax, lowering ribs

  2. Diaphragm relaxes

  3. Thoracic volume decreases, pressure increases, air forced out of lungs

  4. Elastic recoil of alveoli helps force air out