Bioenergetics

• Word equation for photosynthesis

  $carbon dioxide +$$water --> glucose +$$oxygen$
• Raw materials needed for photosynthesis

  • Carbon dioxide
  • Water
• Symbol equation for photosynthesis

  6CO2 + 6H2O --> C6H12O6 + 6O2
• What type of energy is needed for photosynthesis?

  • Light energy
  • Chloroplasts absorb light energy for photosynthesis
• What type of reaction is photosynthesis?

  Endothermic

  • Energy is transferred from the environment to the chloroplasts by light
• 4 factors that affect the rate of photosynthesis

  1. Carbon dioxide concentration
  2. Light Intensity
  3. Temperature
  4. Amount of chlorophyll
• Describe AND explain the graph of light intensity versus rate of photosynthesis

  • As the light intensity increases, the rate of photosynthesis steadily increases to a certain point. Beyond this point, either carbon dioxide concentration or temperature become the limiting factor. Light intensity is no longer the limiting factor. The rate of photosynthesis levels off, although the light intensity continues to increase.

  
• Describe and explain how increasing carbon dioxide concentration affects the rate of photosynthesis

  As the carbon dioxide concentration increases, the rate of photosynthesis steadily increases until either light intensity or temperature become the limiting factor. The rate of photosynthesis levels off even though the carbon dioxide concentration continues to increase.
• How does increasing temperature affect the rate of photosynthesis?

  • Temperature increases the rate of photosynthesis until the optimum temperature is reached.
  • But usually after 45 degrees, the enzymes that control photosynthesis denature and the rate of photosynthesis decreases until photosynthesis stops occurring, as enzymes lose their function.
• At night 


  • Light intensity is usually the limiting factor
  • Much brighter during the day
• In winter

  • Temperature is usually the limiting factor
• If it's warm enough and bright enough

  • Carbon dioxide level is usually the limiting factor
• Limiting factor

  • A factor which stops increasing the rate of photosynthesis
• When is chlorophyll a limiting factor of photosynthesis?

  • Variegated (non-green) leaves
• Greenhouses

  • Creates an environment by enhancing the conditions to maximise the rate of photosynthesis in order to maximise plant growth.
  • Whilst still maintaining a profit.
• Artificial ways to increase limiting factors in greenhouse

  • Carbon dioxide levels can be increased by installing paraffin heaters. When they burn in oxygen, they release carbon dioxide.
  • Temperature = Paraffin heaters, ventilation, greenhouses trap heat.
  • Light intensity = Artificial light during the night
• Maintaining general health of plants using greenhouses

  1. Makes it easier to keep plants away from pests and pathogenic diseases.
  2. The father can add fertilisers to provide mineral ions, nutrients essential for growth, insecticides in the soil.
• Greenhouse costs and profits

  • If the farmers can keep the conditions just right for photosynthesis, the plants will grow much faster and a decent crop can be harvested so more can be sold.
  • Increases the conditions just enough because if its more than the plant needs, that would be a waste of money.
• Investigating the rate of photosynthesis : Pondweed experiment

  • The rate at which the pondeed produces oxygen corresponds to the rate at which the pondweed is photosynthesising.
• Pondweed experiment : Independent variable

  Light intensity

  • controlled by the distance from the plant to the lamp
• Pondweed experiment : Dependent variable

  Volume of oxygen produced

  • measured by the length of the bubble
• Pondweed experiment : Control variable

  • Temperature of the water bath
  • Type of pondweed
  • Cutting of pondweed
• Pondweed experiment : Improving accuracy

  • Repeat twice more with the light source at the same distance, identify anomalies and calculate mean volume of oxygen produced.
• Whole Pondweed experiment is repeated

  • At different distances from the light source to the pondweed
• Rate of photosynthesis calculation

  • Length of oxygen bubble / minutes it was produced
  • cm/min
• Problems / limitations with pondweed experiment

  • Hard to count all bubbles / of different sizes.
  • Experiment assumes that all oxygen from photosynthesis is given off - ignores use of oxygen in respiration.
• Improvements in pondweed experiment

  • Collect oxygen gas in a gas syringe
  • Then rate of photosynthesis would be calculated by volume/min, c m^3/ min
• 5 uses of glucose produced by photosynthesis :

  1. Respiration
  2. Converted into insoluble starch for storage / later use
  3. Storage of lipids and oils
  4. Produce cellulose which supports and strengthen cell walls
  5. Produce amino acids by protein synthesis
• What do plants use in addition to glucose to produce proteins?

  • Nitrate ions that are absorbed from the soil by active transport
• As the distance from the light source to the pondweed increases...

  • Light intensity decreases.
  • Therefore, distance and light intensity are inversely proportional to eachother.
• Law that links light intensity and distance

  $Light intensity =$$1/(distance)^2$
• Understanding the Inverse Square Law

  • If the distance from the light source to the pondweed is halved, the light intensity will be 4x greater.
  • If the distance from the light source is doubled, the light intensity will be 4x times smaller.
• What is Respiration?

  • An exothermic reaction which is continuously occurring in living cells.
  • The energy transferred supplies all the energy needed for living processes.
• Why is respiration exothermic?

  • Because it transfers energy to the environment
• What do organisms need respiration for?

  • muscle contraction for movement
  • maintain body temperature
  • Building large molecules : Make proteins from amino acids for growth
  • For active transport (plants, small intestine)
• Aerobic respiration

  • Respiration using glucose + OXYGEN
• Word equation for aerobic respiration

  • glucose + oxygen ---> carbon dioxide + water
  • Energy is released
• Symbol equation for aerobic respiration

  • C6H12O6 + 6O2 --> 6CO2 + H2O
• Site of aerobic respiration

  • mitochondria
• Site of anaerobic respiration

  • Cytoplasm