respiration & gas exchange

• Respiration is a chemical process where glucose is broken down to release energy to carry out different cellular processes
• Respiration happens in almost all cells in the body
• Respiration is controlled by enzymes
• Breathing


  The physical process of inhaling oxygen and exhaling carbon dioxide in and out of our lungs
• Respiration


  The chemical process which releases energy from glucose
• Uses of energy in living organisms


  • Muscle contraction
  • Protein synthesis
  • Cell division
  • Active transport
  • Growth
  • Passage of nerve impulses
  • Maintenance of a constant body temperature
• Investigating the effect of temperature on respiration


  1. Add yeast and glucose solution to a test tube

  2. Place the test tube in a water bath of 30 degrees Celsius

  3. Add a drop of methylene blue

  4. Start the timer

  5. Shake for 10 seconds

  6. Record how long it takes for methylene blue to turn colorless
• Variables in the experiment


  • Independent variable: Temperature

  Dependent variable: Rate of respiration

  Controlled variables: Amount of methylene blue dye, amount of yeast suspension, concentration of glucose, pH
• As temperature increases up to 40 degrees Celsius

  The rate of respiration increases
• Beyond 40 degrees Celsius

  The rate of respiration decreases
• Respiration can take place aerobically (with oxygen) or anaerobically (without oxygen)
• Aerobic respiration


  The chemical reactions in cells that use oxygen to break down nutrient molecules to release energy
• Aerobic respiration


  Glucose + Oxygen → Carbon dioxide + Water
• Anaerobic respiration


  The chemical reactions in cells that break down nutrient molecules to release energy without using oxygen
• Anaerobic respiration in yeast

  Glucose → Alcohol + Carbon dioxide
• Anaerobic respiration in muscle cells during vigorous exercise

  Glucose → Lactic acid
• Anaerobic respiration releases much less energy per glucose molecule than aerobic respiration
• Lactic acid builds up in muscle cells during anaerobic respiration, causing cramps and muscle fatigue
• After exercise, the heart rate continues to be fast to transport lactic acid from muscles to the liver, where it is converted to carbon dioxide and water through aerobic respiration
• Oxygen debt


  The temporary shortage of oxygen during vigorous exercise
• Even after exercise, we continue to breathe deeper and faster to supply sufficient oxygen for aerobic respiration of lactic acid to repay the oxygen debt
• Respiration


  A chemical reaction in cells that breaks down nutrients to release energy
• Types of respiration


  • Aerobic respiration
  • Anaerobic respiration
• Enzymes are absolutely necessary for respiration reactions to occur
• Uses of energy from respiration


  • Muscle contraction
  • Protein synthesis
  • Cell division
  • Active transport
  • Growth
  • Passage of nerve impulses
  • Maintenance of constant body temperature
• Aerobic respiration


  Chemical reactions of cells that use oxygen to break down nutrient molecules to release energy
• Investigating aerobic respiration using a simple respirometer

  1. Place organisms in specimen chamber

  2. Soda lime absorbs carbon dioxide

  3. Measure rate of oxygen uptake by organisms

  4. Use water bath to control temperature
• Soda lime can absorb carbon dioxide already present in the air, not just that produced by respiration
• Need a control experiment with glass beads instead of soda lime to account for this
• Anaerobic respiration


  Chemical reactions in cells that break down nutrient molecules to release energy without using oxygen
• Anaerobic respiration is less efficient than aerobic respiration, producing less energy per molecule of glucose
• Anaerobic respiration in humans


  1. Glucose

  2. Lactic acid
• During vigorous exercise


  Oxygen demand is higher than supply, leading to anaerobic respiration
• Anaerobic respiration produces lactic acid


  Lactic acid needs to be removed by aerobic respiration
• After vigorous exercise


  Heart rate and breathing remain elevated to remove lactic acid via aerobic respiration
• Respiration


  The chemical reactions that break down nutrient molecules in living cells to release energy
• Energy in the human body


  • Muscle contraction
  • Protein synthesis
  • Growth
  • Cell division
  • Passage of nerve impulses
  • Maintenance of constant body temperature
• Aerobic respiration


  The release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of oxygen
• Aerobic respiration


  Glucose + Oxygen = Carbon dioxide + Water
• Anaerobic respiration


  The release of a relatively small amount of energy by the breakdown of food substances in the absence of oxygen