Biology Chapter Four

• Photosynthesis


  Carbon dioxide + water → Glucose + oxygen
• Photosynthesis


  • Endothermic reaction
  • Energy supplied by sunlight
• Temperature increases


  Rate of photosynthesis increases
• CO2 increases


  Rate of photosynthesis increases
• Light intensity increases


  Rate of photosynthesis increases
• Glucose


  Source of chemical energy when broken down during respiration
• Glucose can be converted into

  • Starch (insoluble)
  • Fat or oil
  • Cellulose
  • Proteins
• Limiting factor


  Factor that stops the reaction going any faster
• Respiration


  Exothermic reaction that releases energy from glucose molecules for use by the body
• Organisms need energy from respiration for


  • Chemical reactions
  • Movement
  • Keeping warm
• Aerobic respiration


  Glucose + oxygen → Carbon dioxide + water
• Anaerobic respiration


  Glucose → Lactic acid (in animals)

  Glucose → Ethanol + carbon dioxide (in plants and yeast)
• During exercise


  Rate of respiration increases
• During rigorous activity


  Muscles may not get enough oxygen, so anaerobic respiration starts
• Lactic acid


  Causes muscles to hurt and stop contracting efficiently, needs to be removed quickly
• Metabolism


  Sum of all the chemical reactions in a cell or in the body, controlled by enzymes and may need energy from respiration
• Metabolism includes


  • Conversion of glucose to starch, glycogen, cellulose

  Conversion of glycerol and fatty acids to lipids

  Conversion of glucose and nitrates to amino acids to synthesise proteins

  Conversion of proteins to urea for excretion
• Anaerobic respiration


  Glucose is not completely broken down, transfers much less energy than aerobic respiration
• Fermentation


  Anaerobic respiration in animals, plants, and yeast to produce ethanol and carbon dioxide
• Required Practical 5: Investigate the effect of light intensity on the rate of photosynthesis

  Place pondweed in beaker

  Add sodium hydrogen carbonate to provide CO2

  Record number of bubbles at different distances from lamp in 1 minute

  Repeat with lamp at different distances