BIO 360: Vertebrate Physiology Lab 4: Oxygen and Aerobic Metabolism Lab 4: Oxygen and Aerobic Metabolism Lab Report KEY Lab report (5 pts each; 15 pts total) 1. Compare the tidal volumes of the 4 breaths you analyzed both at rest and post-­‐exercise. Is it important for this experiment that resting and post-­‐exercise tidal volumes be similar? Answers will vary. You were asked to take deep breaths, but these were not standardized. Overall, however, the differences in volumes will not affect the outcome of the experiment because O2 uptake and use is dependent on tissue metabolism (rate that tissues consume O2), not on the frequency/deepness of breath. (i.e we can only use a certain amount of inhaled O2, regardless of how much of it we breath in.) Since we are calculating the O2 consumed, we will be factoring in both O2 concentration in the air and total volume of inhaled air (tidal volume.) 2. Inhaled oxygen should have the same concentration at rest and post-­‐exercise (approximately 21%), yet the peak oxygen concentration values in the post-­‐exercise run never achieve this value. What aspect of the experimental design accounts for this finding? Inhaled O2 is based on the concentration of O2 available in the air – 20.95%, which will not change before or after exercise. The entire curve is shifted downward in the post-­‐exercise graph because CO2 remains in the apparatus. Some of the air in the apparatus is then re-­‐breathed, leading to lower O2 concentrations overall. However, this does not affect the % of O2 extracted and used by our cells, which is the aspect of the experimental design that is important. 4. CO2 was not measured. What would you expect the volume of exhaled CO2 to be in this experiment at rest and after exercise? The volume of CO2 exhaled should be approximately equal to the volume of O2 inhaled, based on the balanced equation for cellular respiration. This question was unintentionally left off the lab report, but it is important to your understanding of these concepts and might help clarify the questions above. Use the average values for Tidal Volume and ∆O2 Concentration (%) from Table 1 to calculate the average O2 consumed pre-­‐ and post-­‐exercise per breath and over the combined 4 breaths: ∆O2 Concentration (%) × Tidal Volume (L) = O2 consumed per breath O2 consumed per breath × 4 breaths = O2 consumed over that time interval Answers will vary based on measurements taken and recorded in Table 1, but should be (much) larger post-­‐exercise for both per breath and over the 30 second time interval.