BIOENERGETICS

• Photosynthesis


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


  1. Uses energy

  2. Changes carbon dioxide and water

  3. Into glucose and oxygen
• Photosynthesis


  • Takes place in chloroplasts in green plant cells
  • Chloroplasts contain pigments like chlorophyll that absorb light
  • Energy is transferred to the chloroplasts from the environment by light
  • Photosynthesis is endothermic - this means energy is transferred from the environment in the process
• Word equation for photosynthesis

  carbon dioxide + water -> glucose + oxygen
• Symbol equation for photosynthesis

  6CO2 + 6H2O -> CH2O + 6O2
• Ways plants use glucose

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


  • Intensity of light
  • Concentration of CO2
  • Temperature
• Limiting factors


  Affect the rate of photosynthesis
• Relationship between light intensity and rate of photosynthesis

  • Rate increases with light intensity up to a point
  • Beyond that, rate no longer increases as either temperature or CO2 level becomes the limiting factor
• Relationship between CO2 level and rate of photosynthesis

  • Rate increases with CO2 level up to a point
  • Beyond that, rate no longer increases as either light or temperature becomes the limiting factor
• Relationship between temperature and rate of photosynthesis

  • Enzymes work more slowly at low temperatures
  • Enzymes are damaged at high temperatures (around 45°C)
• Chlorophyll can also be a limiting factor of photosynthesis
• The Rate of Photosynthesis

  1. One Graph May Show the Effect of Many Limiting Factors

  2. The graph shows how the rate of photosynthesis is affected by light intensity and temperature

  3. The graph shows how the rate of photosynthesis is affected by light intensity and CO2 concentration
• As the light intensity increases


  The rate of photosynthesis increases steadily
• When light is no longer the limiting factor

  The lines level off
• The line at 25 °C levels off at a higher point than the one at 15 °C


  Temperature must have been a limiting factor at 15 °C
• The line at the higher CO2 concentration of 0.4% levels off at a higher point than the one at 0.04%


  CO2 concentration must have been a limiting factor at 0.04% CO2
• Inverse Square Law


  Light intensity decreases in proportion to the square of the distance
• If you halve the distance, the light intensity will be four times greater and if you third the distance, the light intensity will be nine times greater
• Respiration


  The process of transferring energy from the breakdown of glucose (sugar), which goes on in every cell in the body continuously
• If you double the distance, the light intensity will be four times smaller and if you treble the distance, the light intensity will be nine times smaller
• Respiration is not "Breathing In and Out"
• Respiration involves many reactions that are really important as they transfer the energy the cell needs for all living processes
• Oxygen Production Shows the Rate of Photosynthesis

  1. A source of white light is placed at a specific distance from the pondweed

  2. The pondweed is left to photosynthesise for a set amount of time

  3. The length of the gas bubble is measured, which is proportional to the volume of O2 produced

  4. The experiment is repeated with the light source at different distances from the pondweed
• Respiration


  • It is the process of transferring energy from glucose
  • It goes on in every cell in the body continuously
  • It happens in plants too, all living things respire
• The apparatus can be altered to measure the effect of temperature or CO2 on photosynthesis
• Respiration is exothermic


  It transfers energy to the environment
• Greenhouses


  • Trap the Sun's heat
  • Ensure temperature doesn't become limiting
  • Use heaters, shades and ventilation to control temperature
  • Provide artificial light after the Sun goes down
  • Increase the level of carbon dioxide
  • Keep plants free from pests and diseases
  • Allow addition of fertilisers to provide minerals
• Sorting all this out costs money, but if the farmer can keep the conditions just right for photosynthesis, the plants will grow much faster and a decent crop can be harvested much more often
• How organisms use the energy transferred by respiration


  • To build up larger molecules from smaller ones
  • In animals to allow muscles to contract
  • In mammals and birds to keep their body temperature steady in colder surroundings
• It's important that a farmer supplies just the right amount of heat, light, etc. enough to make the plants grow well, but not more than the plants need, as this would just be wasting money
• Metabolism


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


  When you exercise, your body responds in different ways to get enough energy to your cells
• Metabolism


  • There are lots of chemical reactions happening all the time in a cell, controlled by enzymes
  • Many of these reactions are linked together to form bigger reactions
  • Some reactions make larger molecules from smaller ones, others break down larger molecules into smaller ones
• Respiration transfers energy but this page has worn me out
• Each individual living cell in the body is respiring every second of every day, transferring energy from the food you eat, which is used to make molecules the cells need
• What happens when you exercise

  1. Muscles need energy from respiration to contract

  2. Increased respiration to get more oxygen into cells

  3. Breathing rate and breath volume increase to get more oxygen into blood

  4. Heart rate increases to get oxygenated blood around body faster

  5. Anaerobic respiration when oxygen supply can't keep up

  6. Lactic acid builds up causing muscle fatigue
• Aerobic respiration


  Respiration using oxygen, the most efficient way to transfer energy from glucose
• Anaerobic respiration


  Respiration without oxygen, leads to lactic acid buildup
• Aerobic respiration


  • It goes on all the time in plants and animals
  • Most of the reactions happen inside mitochondria
  • Word equation: glucose + oxygen -> carbon dioxide + water