Bioenergetics

• Epidemiology studies


  Look at levels of health and illness in a population to identify risk factors
• Leaf cross-section


  Palisade mesophyll (photosynthesis), cuticle, upper/lower epidermis, spongy mesophyll (gas exchange), guard cells/stomata
• Xylem


  Carries water upwards from roots to leaves
• Phloem


  Carries ions and food downwards from leaves to roots
• Factors affecting transpiration rate

  • Bright light
  • High temperature
  • High wind
  • Low humidity
• Photosynthesis is an endothermic reaction that takes in energy
• Requirements for photosynthesis


  • Chlorophyll
  • Water
  • Carbon dioxide
  • Sunlight
• Increasing carbon dioxide percentage

  Increases rate of photosynthesis up to a point
• Increasing light intensity


  Increases rate of photosynthesis up to a point
• Increasing temperature


  Increases rate of photosynthesis up to an optimal point, then decreases as enzymes denature
• Glucose from photosynthesis is stored as starch, e.g. in potatoes
• Respiration


  Takes glucose, adds oxygen, produces water and carbon dioxide
• Respiration is an exothermic reaction that releases energy
• Anaerobic respiration


  Converts glucose to energy and lactic acid without oxygen
• Anaerobic respiration in yeast converts glucose to ethanol and carbon dioxide
• Metabolism


  The rate that chemical reactions take place in the body
• Examples of metabolism


  • Glucose to starch, cellulose or glycogen
  • Fatty acids and glycerol to lipids
  • Amino acids to proteins
  • Glucose and nitrate ions to amino acids
  • Proteins to urea
• Bacteria divide very rapidly, from one to millions in a short time