[BIO 11.1] E5 - Respiration

• Respiration is a process done by all cells where organic compounds (ex. glucose) are broken down to release energy, mostly in the form of adenosine triphosphate (ATP).
• Cellular respiration can be aerobic or anaerobic; with or without oxygen.
• Aerobic respiration:

  C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy

  Considered more efficient as it generates more energy for the amount of glucose inputted
• Anaerobic respiration:

  C6H12O6 -> energy + (ethanol + CO2) or lactic acid
• Consumption of Oxygen

  In the laboratory, mung beans were used to observe the effects of oxygen presence on anaerobic respiration.

  The flask with water caused greater growth, while the one with alkaline pyrogallol stunted the growth of the seed’s roots.
• The alkaline pyrogallol sequesters the water in the flask, preventing aerobic respiration.
• Anaerobic Respiration

  Fermentation is a process undergone by yeast to extract energy from glucose. Yeast was examined in the laboratory to observe trends in anaerobic respiration.
• Production of Carbon Dioxide

  Carbon dioxide in the form of carbonic acid can react with barium hydroxide to form a white precipitate, barium carbonate:

  H2CO3 + Ba(OH)2 -> BaCO3 + 2H2O.
• A setup consisted of two flasks, sealed by rubber stoppers, and connected by glass tubing.

  a.) 10% glucose and Ba(OH)2 setup - Some white precipitate forms in the Ba(OH)2 flask. This is caused by existing atmospheric CO2 that was sealed with the flask

  b.) yeast-glucose solution and Ba(OH)2 setup - More white precipitate formed in the Ba(OH)2 flask. This is evidence that yeast produces CO2 as a product of fermentation.
• Effects of Substrate and Temperature

  Glucose is a monosaccharide, which is very easy to break down. Sucrose is a disaccharide of glucose and fructose, and it must be broken down into its components to be used.
• The complexity of the substrate has an inverse relationship with the rate of fermentation. The rate of fermentation also has a direct relationship with the concentration of substrate, until a certain point where the rate won’t increase anymore.
• Yeast fermentation is also affected by temperature. The rate of fermentation increases up to a certain temperature (according to the experiment, its optimal temperature is 40°C). This is caused by the activation of yeast due to temperature.

  However, yeast cells are also a living organism. Beyond this optimal temperature, the rate of fermentation decreases, as the yeast begins to lose activity, or even dies. This looks like a bell curve.