Bioenergetics

• Photosynthesis

  The process through which a plant makes its own food using carbon dioxide and water
• Things needed for photosynthesis

  • Water
  • Carbon dioxide
  • Sunlight
  • Chlorophyll
• Photosynthesis

  Carbon dioxide + Water → Glucose + Oxygen
• Photosynthesis is an endothermic reaction - energy is transferred from the environment to the chloroplasts in the plant
• Factors that can limit the rate of photosynthesis

  • Temperature
  • CO2
  • Light
  • Amount of chlorophyll
• Temperature

  • The best temperature is about 40°C - anything above 30°C will slow photosynthesis right down
  • this is because temperature gives particles kinetic energy, increasing the chance that reactants bump into each other
• CO2

  • If there is more carbon dioxide, photosynthesis will happen quicker
  • this is because it is one of the raw products required for photosynthesis
  • increase will continue until maximum efficiency is reached
• Light

  • If there is more light, photosynthesis happens faster
  • this continues until either maximum productivity is reached or another factor becomes limiting
• Amount of chlorophyll

  • The more chlorophyll, the more photosynthesis
• Photosynthesis is controlled by enzymes - these are destroyed at temperatures above 40°C
• Calculating intensity

  Light intensity = 1/distance squared
• Uses of glucose produced by photosynthesis

  • Respiration

  Making starch

  Making cellulose for cell walls

  Making amino acids for protein synthesis

  Making lipids (fats or oils) to store in seeds
• Respiration

  The process our bodies use to produce energy, an exothermic reaction
• (Aerobic) Respiration

  Glucose + Oxygen → Water + Carbon Dioxide + Energy
• Uses of energy from respiration

  • Building up sugars in plants

  Building up body tissue

  Maintaining a constant body temperature (warm-blooded mammals only)

  Building up amino acids and nitrates

  movement

  active transport

  protein synthesis

  passage of nerve signals
• Anaerobic respiration

  Energy is provided without needing oxygen
• Anaerobic respiration produces energy much quicker than aerobic respiration but only produces 1/20th as much
• Lactic acid

  Can build up in muscles causing fatigue and an oxygen debt, which then needs to be repaid by deep breathing to oxidise the lactic acid
• Anaerobic respiration in plants and yeast

  Glucose → Ethanol + Carbon Dioxide
• Anaerobic respiration in plants and yeast is called "fermentation" and is widely used in the manufacture of bread and alcoholic drinks
• During exercise

  Heart rate increases, breathing increases, and arteries supplying muscles dilate - these help muscles get the oxygen and glucose they need
• Blood flowing through the muscles transports lactic acid to the liver where it is converted back into glucose. Oxygen debt is the amount of extra oxygen the body needs to break down the lactic acid and remove it.
• Metabolism

  The sum of all the reactions in a cell or body
• Processes included in metabolism

  • Conversion of glucose to starch, glycogen and cellulose

  Turning glycerol and fatty acids into lipids

  Turning glucose and nitrates into amino acids

  Respiration

  Breaking down excess proteins to form urea