Unit 4 - Bioenergetics

• Photosynthesis is an endothermic reaction as it takes in energy in the form of light.
• The equation for photosynthesis is glucose + water → oxygen + carbon dioxide
• Uses of glucose:

  • Release energy in respiration
  • Produce insoluble storage molecule starch
  • Converted into fats and oils as storage
  • Cellulose for strength in cell wall
  • Produce amino acids to synthesis proteins (needs nitrate ions)
• Farmers want to increase photosynthesis to increase yield of crops
• Greenhouses:

  • Shades removed from ceiling to allow maximum light
  • Artificial light during winter / darker hours
  • Greenhouse traps the sun's heat so temperature does not limit photosynthesis
  • Heater burns paraffin and produces CO2
• Plants need nitrates to make amino acids that are needed to make proteins
• 3 uses of energy:

  • Movement
  • Keep warm
  • Chemical reactions for building larger molecules
• Respiration is an exothermic reaction because it releases energy
• Lactic acids causes muscles to become fatigued and stop contracting efficiently
• Lactic acid is transported out of muscles by blood to the liver and converted back to glucose by reacting with oxygen.
• Oxygen debt - the amount of extra oxygen the body needs to react with the accumulated lactic acid and remove it from the cells
• Metabolism reactions with glucose in plants

  • Respiration -> glucose
  • Glucose -> cellulose to strengthen plant cell wall
  • Glucose -> starch for storage
  • Glucose + nitrate ions -> amino acids for protein synthesis
• Metabolism reactions with glucose in humans

  • Glucose -> glycogen
• Metabolism:

  • 1 glycerol molecule + 3 fatty acids -> lipids (found in the cell membrane)
  • Excess proteins -> urea (excreted by kidneys)
• Exercise:

  1. Increased demand for energy so increased aerobic respiration so body cells need more oxygen
  2. Breathing rate and breathing volume increases - supplies more oxygen to lungs, so more oxygen to blood and more carbon dioxide is removed
  3. Heart rate increases - increases blood flowing to muscles to provide more oxygen to provide more glucose, remove carbon dioxide more quickly and to remove lactic acid quicker
  4. Anaerobic respiration - not enough oxygen, leads to build up of lactic acid, causing muscles to become fatigued and stop contracting efficiently
  5. Oxygen debt