B8 and B9 Photosynthesis and respiration

• Equation for aerobic respiration

  Glucose + oxygen → carbon dioxide + water + energy
• Equation for anaerobic respiration in mammals

  Glucose → lactic acid + energy
• Anaerobic respiration in mammals

  • Results in oxygen debt so need to breathe heavily after the exercise
  • Oxygen then reacts with the lactic acid to cancel it out
• Equation for anaerobic respiration in plants and yeast

  Glucose → carbon dioxide + ethanol + energy
• Anaerobic respiration in plants and yeast


  • Produces a gas = makes bread rise
  • Produces alcohol = makes beer & wine
• During exercise


  • Heart rate increases
  • Volume of blood per beat increases
  • Breathing rate & volume increases
• Why pulse and breathing rate increase during exercise

  • More blood flowing to muscles so more oxygen and glucose delivered = faster rate of respiration = more energy
  • Blood flow needs to increase to remove waste products such as carbon dioxide & bring back to lungs for diffusion
• Metabolism


  The sum of all chemical reactions in the body
• Examples of metabolism


  • Conversion of glucose to starch or glycogen
  • Making lipids
  • Making amino acids from glucose and nitrates
  • Respiration/ photosynthesis
  • Breakdown of excess proteins to form urea
• Equation for photosynthesis

  Carbon dioxide + water → oxygen + glucose

  
• What the plant uses the glucose for

  • Used in respiration
  • Stored as starch
  • Stored as fats and oils
  • Makes cell walls (cellulose)
  • Makes amino acids which are turned into proteins
• As temperature increases

  Rate of photosynthesis increases, until it reaches the optimum temperature and then the rate decreases

  
• Why temperature affects photosynthesis rate

  • As temperature increases the particles have more kinetic energy so there are more successful collisions = faster rate of photosynthesis
  • After the optimum temp, the chlorophyll (enzyme) denatures, so the rate of photosynthesis decreases

  
• As carbon dioxide concentration increases

  Rate of photosynthesis increases, then it levels off

  
• Why carbon dioxide concentration affects photosynthesis rate

  Carbon dioxide is a reactant in photosynthesis, so the greater the concentration the faster the rate. After a point another factor is limiting the rate (e.g. light intensity) so the rate levels off

  
• As light intensity increases

  Rate of photosynthesis increases, then it levels off

  
• Why light intensity affects photosynthesis rate

  As light intensity increases there is a more energy for the reaction, so a faster rate of reaction. After a point, the increased light intensity does not increase rate as another factor is limiting the rate
• Investigating the effect of light intensity on rate of photosynthesis

  1. Cut a 5cm piece of pondweed

  2. Put the piece of pondweed in a boiling tube of sodium hydrocarbonate to keep the concentration of carbon dioxide the same

  3. Put a light 5cm away from the pondweed

  4. Count the number of bubbles produced in 2 mins

  5. Repeat 3 times

  6. Repeat for other distances = 10cm, 20cm, 30 cm, 40cm

  7. Calculate a mean for each distance
• Control variables


  • Concentration of carbon dioxide