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
• As carbon dioxide concentration increases

  The rate of photosynthesis increases
• As temperature increases


  The rate of photosynthesis increases (up to an optimum temperature)
• As temperature continues to increase beyond the optimum


  The rate of photosynthesis decreases rapidly as enzymes denature
• Greenhouse conditions


  Adjusting light intensity, carbon dioxide concentration, and temperature to maximise the rate of photosynthesis while considering energy costs
• Measuring the rate of photosynthesis


  1. Counting bubbles of oxygen produced per minute

  2. Measuring the volume of oxygen produced per minute
• Controlling variables in photosynthesis rate experiment


  • Same pondweed, length, temperature, carbon dioxide concentration
  • Repeat experiment 3 times for each condition and take the mean
• Changing conditions in photosynthesis rate experiment


  1. Change light intensity by adjusting lamp brightness

  2. Change light colour by using filters
• Inverse Square Law


  Light intensity is proportional to 1/distance^2
• As distance from light source doubles


  Light intensity decreases to 1/4 of the original
• As distance from light source increases


  Rate of photosynthesis decreases proportionally
• 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
• During exercise


  Breathing rate and heart rate increase to supply more oxygen and glucose for aerobic respiration in working muscles
• If not enough oxygen available during exercise


  Anaerobic respiration occurs, producing lactic acid and causing oxygen debt
• Removing lactic acid after exercise


  1. Lactic acid transported to liver

  2. Converted to glucose

  3. Removed from blood
• Oxygen debt


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


  1. Glucose to starch

  2. Glucose to cellulose

  3. Glucose + nitrate ions to amino acids
• Metabolism examples in animals


  1. Glycerol + 3 fatty acids to lipids

  2. Excess amino acids broken down to urea for excretion

  3. Glucose to glycogen for storage
• Metabolism is the sum of all chemical reactions in a cell or body, in both plants and animals