topic 4

• Photosynthesis


  Process that happens in plants and algae where carbon dioxide from the air enters the leaves by diffusion, water from the soil enters the roots by osmosis, sunlight is absorbed by chlorophyll in chloroplasts, and glucose is produced with oxygen as a waste product
• Photosynthesis


  Carbon dioxide + water → glucose + oxygen
• Endothermic reaction


  Energy is transferred from the surroundings to chloroplasts by light
• Uses of glucose produced in photosynthesis

  • Used in respiration to release energy
  • Converted to insoluble starch for storage
  • Used to make fats or oils for energy storage
  • Used to produce cellulose to strengthen cell walls
  • Combined with nitrates to make amino acids for proteins
• Limiting factors in photosynthesis

  • Light intensity
  • Carbon dioxide concentration
  • Temperature
  • Amount of chlorophyll present
• As light intensity increases

  The rate of photosynthesis increases
• When light intensity is no longer limiting


  The rate of photosynthesis does not increase further, carbon dioxide concentration or temperature are limiting
• As carbon dioxide concentration increases

  The rate of photosynthesis increases
• When carbon dioxide concentration is no longer limiting


  The rate of photosynthesis does not increase further, light intensity or temperature are limiting
• As temperature increases


  The rate of photosynthesis increases
• As temperature continues to increase

  The rate of photosynthesis decreases rapidly as enzymes denature
• Measuring the rate of photosynthesis

  • Counting bubbles of oxygen produced per minute
  • Measuring volume of oxygen produced per minute
• Measuring rate of photosynthesis using pondweed

  1. Set up apparatus with pondweed, lamp, and ruler

  2. Add sodium bicarbonate to provide excess carbon dioxide

  3. Move lamp to different distances, wait for rate to stabilize, then count bubbles per minute

  4. Repeat for 5-6 different distances

  5. Plot graph of bubbles per minute vs distance
• Control variables for photosynthesis rate experiment


  • Same pondweed, length, temperature, carbon dioxide concentration
  • Repeat experiment 3 times for each distance to take a mean
• Measuring rate of photosynthesis by changing light intensity


  1. Vary brightness of bulb instead of distance

  2. Use color filters to change light color
• Inverse Square Law


  Light intensity is proportional to 1/distance^2
• Inverse Square Law example

  • Distance doubled from 10cm to 20cm, light intensity reduced to 1/4
  • Rate of photosynthesis also reduced to 1/4
• Inverse square law


  Light intensity is inversely proportional to the square of the distance from the light source
• Inverse square law example

  1. Distance doubled

  2. Light intensity reduced to a quarter

  3. Photosynthesis rate reduced to a quarter
• Respiration


  Process that provides energy for all living things, it is exothermic and happens continuously in living cells
• Respiration


  • Can be aerobic (using oxygen) or anaerobic (without oxygen)
• Aerobic respiration


  1. Oxygen taken into lungs

  2. Glucose from digestive system transported in blood

  3. Respiration in cells releases energy, carbon dioxide and water
• Aerobic respiration equation


  Glucose + Oxygen → Carbon dioxide + Water
• Anaerobic respiration in animal cells

  Glucose converted to lactic acid, less energy released
• Anaerobic respiration in plant and yeast cells

  Glucose converted to ethanol and carbon dioxide, much less energy released
• Fermentation


  Anaerobic respiration in yeast, produces carbon dioxide which makes bread dough rise, also produces ethanol for alcoholic drinks
• Comparison of aerobic and anaerobic respiration in plants, animals and yeast

  • Tick/cross grid
• Response to exercise


  1. Increased breathing rate

  2. Increased heart rate

  3. Increased aerobic respiration in muscle cells

  4. Anaerobic respiration can occur, leading to lactic acid buildup and oxygen debt
• Metabolism of lactic acid after exercise

  1. Lactic acid transported in blood to liver

  2. Converted back to glucose in liver
• Oxygen debt


  Extra oxygen needed after exercise to react with and remove lactic acid from cells
• Metabolism examples


  • Glucose to starch (plants)
  • Glucose to cellulose (plants)
  • Glucose + nitrate to amino acids (plants and animals)
  • Glycerol + fatty acids to lipids (plants and animals)
  • Excess amino acids to urea for excretion (animals)
  • Glucose to glycogen for storage (animals)