bioenergetics

• Photosynthesis

  The process by which plants use sunlight, water and carbon dioxide to create oxygen and energy in the form of sugar
• Photosynthesis


  Carbon dioxide + Water → Glucose + Oxygen
• Photosynthesis is an endothermic reaction
• Limiting factors affecting rate of photosynthesis

  • Temperature
  • Carbon dioxide concentration
  • Light intensity
  • Chlorophyll concentration
• As temperature increases


  Rate of photosynthesis increases
• As temperature approaches 45°C

  Rate of photosynthesis drops to zero
• As carbon dioxide concentration increases

  Rate of photosynthesis increases
• As light intensity increases

  Rate of photosynthesis increases
• Chlorophyll concentration does not vary in the short term but may change if plants are grown in soil without enough minerals
• Inverse square law


  When light intensity is studied, doubling the distance between the lamp and the pondweed will reduce the light intensity by a quarter
• Converting glucose produced in photosynthesis

  1. Used in respiration to provide energy

  2. Changed into starch, fats/oils, cellulose, proteins
• Nitrate ions are needed to make proteins because amino acids contain nitrogen, but glucose does not
• Respiration


  An exothermic reaction that releases energy from glucose molecules for use by the body
• Reasons organisms need energy from respiration


  • For chemical reactions to build larger molecules
  • For movement
  • To keep warm
• Aerobic respiration


  Respiration with oxygen
• Anaerobic respiration


  Respiration without oxygen
• Aerobic respiration


  Glucose + Oxygen → Carbon dioxide + Water
• Anaerobic respiration in animals

  Glucose → Lactic acid
• Anaerobic respiration in plants and yeast

  Glucose → Ethanol + Carbon dioxide
• Fermentation

  Anaerobic respiration in yeast cells
• During exercise


  Heart rate, breathing rate and breath volume increase to supply muscles with more oxygen and glucose for aerobic respiration
• During vigorous exercise


  Muscles may not get enough oxygen, so anaerobic respiration starts in muscle cells
• Oxygen debt


  The amount of extra oxygen the body needs after exercise to react with the lactic acid and remove it from cells
• Lactic acid causes muscles to hurt and stops them contracting efficiently. It is a poison that needs to be removed quickly.
• After exercise, lactic acid is transported to the liver where it is broken down.
• Metabolism


  The sum of all the chemical reactions in a cell or in the body, continually controlled by enzymes
• Metabolism includes the conversion of glucose to starch, glycogen and cellulose, the formation of lipid molecules, the use of glucose and nitrate ions to form amino acids for proteins, and the breakdown of excess proteins into urea for excretion.
• Respiration in cells can be aerobic (with oxygen) or anaerobic (without oxygen)
• The equation for aerobic respiration is the same in all organisms
• In anaerobic respiration, the glucose is not completely broken down
• Anaerobic respiration transfers much less energy than aerobic respiration
• The process of anaerobic respiration is different in animals to the process found in plants and yeast
• Anaerobic respiration in animals


  Lactic acid is produced
• Photosynthesis

  Carbon dioxide + water + light energy → Glucose + Oxygen
• Respiration

  Process that releases energy from glucose, occurs in mitochondria
• Photosynthesis only produces glucose during the day

  Plant cells respire all the time, including at night
• Starch

  Insoluble storage molecule produced from glucose, can be converted back to glucose when needed
• Fats and oils


  Storage form of energy produced from glucose in many plants
• Cellulose

  Molecule in plant cell walls, made from glucose produced by photosynthesis
• Amino acids

  Produced from glucose, used by plants to synthesize proteins