Topic 4-bioenergetics

• Photosynthesis


  Process that uses energy to change carbon dioxide and water into glucose and oxygen
• Photosynthesis


  1. Takes place in chloroplasts in green plant cells

  2. Chloroplasts contain pigments like chlorophyll that absorb light

  3. Energy is transferred to the chloroplasts from the environment by light

  4. Photosynthesis is endothermic
• Endothermic


  Energy is transferred from the environment in the process
• Photosynthesis equation


  Carbon dioxide + water -> glucose + oxygen
• Ways plants use glucose


  • For respiration
  • Making cellulose
  • Making amino acids
  • Stored as oils or fats
  • Stored as starch
• Limiting factors


  Factors that affect the rate of photosynthesis (light intensity, CO2 concentration, temperature)
• Light intensity increases


  Rate of photosynthesis increases up to a point
• CO2 concentration increases


  Rate of photosynthesis increases up to a point
• Temperature increases


  Rate of photosynthesis increases up to a point, then enzymes are destroyed
• Chlorophyll can also be a limiting factor of photosynthesis
• Factors like disease or environmental stress can reduce chlorophyll and slow photosynthesis
• Inverse square law


  Light intensity decreases in proportion to the square of the distance
• Experiment to measure effect of light intensity on photosynthesis


  1. Use Canadian pondweed

  2. Measure oxygen production

  3. Vary light intensity by changing distance of light source
• Greenhouses help trap heat and control temperature, light, CO2 and pests to create ideal conditions for plant growth
• Farmers can use artificial lighting, heaters, ventilation and CO2 sources in greenhouses to optimise conditions for photosynthesis
• Greenhouse conditions


  • Ventilation to cool things down
  • Artificial light after the Sun goes down to give plants more quality photosynthesis time
• Increasing carbon dioxide in greenhouse


  • Using a paraffin heater to heat the greenhouse, as the paraffin burns it makes carbon dioxide as a by-product
• Keeping plants enclosed in a greenhouse


  • Easier to keep them free from pests and diseases
• Farmer adding fertilisers to the soil


  • Provide all the minerals needed for healthy growth
• Farmer keeps conditions just right for photosynthesis


  Plants will grow much faster and a decent crop can be harvested much more often
• It's important that a farmer supplies just the right amount of heat, light, etc. for the plants to grow well, but not more than the plants need, as this would just be wasting money
• Don't blame it on the sunshine, don't blame it on the CO₂...
• Inverse square law


  Relationship between the intensity of light and the distance from the light source
• Respiration


  The process of transferring energy from the breakdown of glucose (sugar)
• Respiration goes on in every cell in your body continuously
• Respiration happens in plants too. All living things respire. It's how they transfer energy from their food to their cells
• Respiration


  The process of TRANSFERRING ENERGY FROM GLUCOSE, which goes on IN EVERY CELL
• Respiration


  Exothermic - it transfers energy to the environment
• How organisms use the energy transferred by respiration


  • To build up larger molecules from smaller ones (like proteins from amino acids)
  • In animals it's used to allow the muscles to contract (so they can move about)
  • In mammals and birds the energy is used to keep their body temperature steady in colder surroundings
• Metabolism


  All the chemical reactions in an organism
• In a cell there are lots of chemical reactions happening all the time, which are controlled by enzymes
• Reactions to form larger molecules

  1. Lots of small glucose molecules are joined together in reactions to form starch (a storage molecule in plant cells), glycogen (a storage molecule in animal cells) and cellulose (a component of plant cell walls)

  2. Lipid molecules are each made from one molecule of glycerol and three fatty acids

  3. Glucose is combined with nitrate ions to make amino acids, which are then made into proteins
• Reactions to break down larger molecules


  1. Glucose is broken down in respiration

  2. Excess protein is broken down in a reaction to produce urea, which is then excreted in urine
• Metabolism


  The sum (total) of all of the reactions that happen in a cell or the body
• Aerobic respiration


  Respiration using oxygen, the most efficient way to transfer energy from glucose
• Aerobic respiration goes on all the time in plants and animals
• Aerobic respiration

  Glucose + oxygen -> carbon dioxide + water
• Anaerobic respiration

  Respiration without oxygen, the incomplete breakdown of glucose, making lactic acid
• Anaerobic respiration in muscle cells

  Glucose -> lactic acid
• Anaerobic respiration does not transfer nearly as much energy as aerobic respiration