bioenergetics

• photosynthesis is the process where plants make glucose from sunlight
• photosynthesis is an endothermic reaction as energy is transferred from the environment to the chloroplasts by light
• carbon dioxide + water $\rightarrow$ glucose + oxygen
• factors affecting rate of photosynthesis - temperature

  • increase in temperature means rate of photosynthesis increases
  • reaction is controlled by enzymes, if temperature keeps increasing the enzymes denature so rate of reaction decreases
• factors affecting the rate of photosynthesis - light intensity

  • the higher the light intensity, the faster the rate of photosynthesis
• factors affecting rate of photosynthesis - carbon dioxide concentration

  • needed to make glucose
  • as concentration increases, rate of reaction increases too
• factors affecting the rate of photosynthesis - amount of chlorophyll

  • chlorophyll is a pigment that converts light energy into plant food
  • if chlorophyll levels are reduced by magnesium deficiency then rate of photosynthesis decreases
• rate of photosynthesis via oxygen production practical

  • pondweed placed in test tube of water, sealed with bung
  • capillary tubes containing water leads in test tube, syringe attatched
  • lamp placed at measured distance from test tube
  • oxygen produced by photosynthesis, gas in capillary tube
  • observe oxygen given off at different light distances
• light intensity = 1 $\div$ distance$^2$
• uses of glucose from photosynthesis

  • respiration
  • converted into insoluble starch for storage
  • fat or oil for storage in seeds
  • cellulose to strengthen cell walls
  • combine with nitrates to form amino acids making proteins
• respiration is an exothermic reaction
• respiration takes place both aerobically with oxygen and anaerobically without oxygen
• during aerobic respiration

  • uses oxygen
  • yields most the energy
  • reactions making up aerobic respiration found in mitochondria
• during anaerobic respiration

  • occurs when there is not enough oxygen
  • does not yield as much energy
  • incomplete oxidation of glucose
  • releases lactic acid
• in animals anaerobic respiration is

  • glucose $\rightarrow$ lactic acid
• anaerobic respiration in plant and leaf cells (fermentation)

  • glucose $\rightarrow$ ethanol + carbon dioxide
• process of fermentation is used to make bread and alcohol
• response to exercise

  • heart rate increases
  • breathing rate increases
  • breath volume increases
• what happens if there is not enough oxygen

  • anaerobic respiration occurs
  • oxygen debt is created
  • muscles tire and cannot contract properly
  • blood flowing through muscles transport lactic acid to liver where it is converted back into glucose
• metabolism is the sum of all chemical reactions in the cell or body controlled by enzymes to maintain optimum cell function
• energy transferred in cells by respiration is used in process of metabolism to make new molecules