Students must be able to interpret specific examples of situations observed in lab and be able to answer questions demonstrating an understanding of the following concepts.
Respiration: the cellular process in which reduced organic compounds are broken down into more oxydized, less energetic, compounds. Some of this liberated energy is used to form of ATP. Aerobic respiration includes glycolysis, the Krebs cycle and the electron transport chain. Students should know where in the cell each occurs.
Aerobic respiration - As observed in germinating seeds, results in the formation of CO2, and the consumption of O2. Triphenyl Tetrazollium Chloride stains germinating grains red as it becomes reduced by the electron transport chain to form a red precipitate. The energy not converted to chemical bond energy of ATP is lost as heat as observed in lab.
View image of set up for measuring carbon dioxide generation by living grains.
View image of jar monitored for oxygen levels
View image of living grain tested positive for respiration using triphenyl tetrazollium chloride.
Efficiency of Respiration.
View image of demonstration of heat loss from lab
Alcoholic fermentation - This is a form of anaerobic respiration. In the absence of O2, there is no receptor for the electrons passed down the electron transport chain, and the Krebs cycle cannot continue. ATP can still produced by glycolysis through the breakdown of glucose into two pyruvates, generating a net return of two ATPs and two NADH+'s. Glycolisis requres NAD. NAD is regenerated from NADH+ in a reaction converting pyruvate into ethanol and CO2, and NADH+ into NAD.
View image of fermenting grape juice
Microcosm Experiment: To better integrate an understanding of the complementary nature of respiration and photosynthesis, an ecology activity to explore the concept of stability is initiated this lab. Students should understand the role of the snails and the plants in this mini ecosystem.
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See answers to questions in the lab manual.
Download completed respiration worksheet