Bioenergetics

• 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 increases further

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

  • Can measure number of oxygen bubbles produced per minute
  • Can measure 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. Plot graph of bubbles per minute vs lamp distance
• Control variables when measuring rate of photosynthesis
• Can also measure rate by changing light intensity instead of distance
• Can also measure rate using different colored light filters
• Inverse square law


  Light intensity is proportional to 1/distance^2
• Inverse square law


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

  • Distance increased from 10 cm to 20 cm, light intensity reduced to 1/4
  • Distance increased from 10 cm to 30 cm, light intensity reduced to 1/9
  • Distance increased from 30 cm to 60 cm, light intensity reduced to 1/4
• Respiration


  Process that provides energy for all living things, can be aerobic (using oxygen) or anaerobic (without oxygen)
• Aerobic respiration


  1. Oxygen taken in through lungs

  2. Glucose from digestive system transported in blood

  3. Respiration in cells releases energy, produces 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 to take in more oxygen

  2. Increased heart rate to supply more oxygenated blood and glucose to working muscles

  3. Anaerobic respiration can occur, producing lactic acid and causing oxygen debt
• Metabolism of lactic acid

  1. Lactic acid transported in blood to liver

  2. Liver converts lactic acid back to glucose
• Oxygen debt


  Extra oxygen needed after exercise to react with and remove lactic acid
• Metabolism examples in plants

  1. Conversion of glucose to starch

  2. Conversion of glucose to cellulose

  3. Conversion of glucose and nitrate ions to amino acids
• Metabolism examples in animals

  1. Formation of lipid molecules from glycerol and fatty acids

  2. Breakdown of excess amino acids to form urea for excretion

  3. Conversion of glucose to glycogen for storage