CH7 Respiration

• Cellular respiration


  Process where glucose reacts with oxygen in body cells to release energy

  
• Types of respiration


  • Aerobic respiration
  • Anaerobic respiration
• Aerobic respiration


  Glucose + oxygen → carbon dioxide + water (+ large amount of energy)

  
• Anaerobic respiration in humans


  Glucose → lactic acid (+ small amount of energy)
• Similarities and differences between aerobic and anaerobic respiration


  • Substrate: glucose
  • Requirement for oxygen: yes for aerobic, no for anaerobic
  • Products formed: carbon dioxide and water for aerobic, lactic acid for anaerobic in humans, carbon dioxide and ethanol for anaerobic in yeast
  • Amount of energy released: large for aerobic, small for anaerobic
• Oxygen debt


  Condition where oxygen demand exceeds oxygen supply, leading to anaerobic respiration and lactic acid production

  
• Oxygen debt repayment


  1. Heart rate remains high to transport lactic acid and oxygen

  2. Breathing remains deep and rapid to supply oxygen for metabolism of lactic acid

  3. Lactic acid is removed from the body

  
• Respiratory system structures


  • Trachea
  • Bronchi and bronchioles
  • Alveoli

  
• Trachea


  • Walls contain C-shaped rings of cartilage to keep lumen open
  • Epithelium contains goblet cells that secrete mucus and epithelial cells with cilia that sweep mucus and trapped particles up
• Alveoli


  • Numerous alveoli increase surface area to volume ratio
  • Epithelium of alveoli and endothelium of associated blood capillaries are one-cell thick to reduce diffusion distance
  • Constant blood flow in associated blood capillaries supplies carbon dioxide and carries away absorbed oxygen
  • Inner walls lined with thin film of moisture to allow oxygen gas to dissolve and diffuse into blood stream

  
• Breathing mechanism: Inhalation


  1. Diaphragm muscles contract and flatten

  2. External intercostal muscles contract

  3. Internal intercostal muscles relax

  4. Ribs move upwards and outwards

  5. Volume of thoracic cavity increases

  6. Pressure in alveoli decreases below atmospheric pressure

  7. Air is forced into the alveoli from the surrounding air

  
• Breathing mechanism: Exhalation


  1. Diaphragm muscles relax and arch upwards

  2. External intercostal muscles relax

  3. Internal intercostal muscles contract

  4. Ribs move downwards and inwards

  5. Volume of thoracic cavity decreases

  6. Pressure in alveoli increases above atmospheric pressure

  7. Air is forced out of the alveoli into the surrounding air

  
• Differences in composition between inspired and expired air

  • Oxygen: ≈21% in inspired, ≈16% in expired
  • Carbon dioxide: ≈0.03% in inspired, ≈4.0% in expired
  • Nitrogen: ≈78% in both
  • Water vapour: variable in inspired, saturated in expired
  • Temperature: variable in inspired, ≈37°C in expired
  • Dust particles: variable in inspired, negligible in expired

  
• Gaseous exchange at the lungs

  1. Higher oxygen concentration in inhaled air than blood

  2. Oxygen dissolves in moisture on alveolar walls and diffuses into blood capillaries and red blood cells

  3. Oxygen binds to deoxyhaemoglobin to form oxyhaemoglobin

  4. Carbon dioxide diffuses from blood into alveolar air space and is excreted

  5. Oxygen is carried by haemoglobin in red blood cells to body tissues

  
• Gaseous exchange at respiring body tissues

  1. Higher oxygen concentration in blood than body cells

  2. Oxygen diffuses from red blood cells to body cells

  3. Higher carbon dioxide concentration in body cells than blood

  4. Carbon dioxide diffuses from body cells into blood capillaries and is carried as hydrogen carbonate ions to lungs
• Effects of smoking cigarettes

  • Nicotine: promotes adrenaline release, increases heart rate and blood pressure, causes addiction, increases risk of blood clots and cardiovascular disease
  • Carbon monoxide: binds to haemoglobin, reduces oxygen carrying capacity of blood, reduces oxygen delivery to tissues and aerobic respiration rate
  • Tar: causes uncontrolled cell division and cancer, paralyses cilia lining trachea and bronchi, causes bronchitis and emphysema