Cell Respiration Lab

PURPOSE 

This lab is based on Cellular Respiration and how temperature of germinating and dominant seeds affect the temperature. We are going to be able to relate gas production with the rate of respiration. 

INTRODUCTION

The germinating seeds are the seeds that are in the process of growing. Cellular Respiration is a catabolic process that produces ATP.  The general formula is 

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

There are three steps to Cellular Respiration Glycolosis, Krebs Cycle, and Electron Transport Chain. Glycolosis occurs in the cytosol and oxideses glucose partially into two pyruvates. Glycolosis unlike Krebs Cycle (Citric Acid Cycle) does not require oxygen.  The Krebs Cycle takes place in the Mitochondria. This process starts with the pyruvates from glycolosis and the pyruvate is now Acetyl-CoA. It is broken down into carbon dioxide. Both Glycolosis and Krebs Cycle produce ATP, but small amounts via Substrate Level Phosphorylization. The Electron Transport Chain is in the inner membrane of the mitochondria. This couples the transfer of electrons between the donor and acceptors of electrons. Consumption and production of carbon dioxide is used to measure Cellular Respiration. 

Method

The first batch that we tested were 25 germinated radish seeds kept at room temperature (which using a thermometer we measured to be 22 degrees Celsius). We placed them into a plastic chamber which got sealed by the CO2 sensor we had connected to our Lab Quest. We let the sensor run for 10 min throughout which we had the Labquest collecting data. Once we had sufficient amount of data, we took the seeds out and placed them into a glass beaker of ice cold water (15 degrees Celsius). After giving them some time to cool off, we took them out, blotted them dry, and repeated the CO2 measurements we had done previously. We then repeated the original process (meaning not including the ice water) with non-germinated radish seeds kept at room temperature and then separately glass beads for the purpose of having a control group.

Data

Graphs Germinated radish seeds, room temperature

 

Germinated radish seeds, ice water

 

Non-germinated radish seeds, room temperature

 

Glass Beads

 

Combined Graph

Discussion

  When the rate of respiration of the germinated radish seeds at 22 degrees Celsius was tested, approximately 0.61 ppm of CO2 per second was found to be produced through the seeds' cellular respiration. The rate of respiration of those same seeds after being soaked in water at 15 degrees Celsius was 0.70 ppm per second. Although most other germinated seeds started to become dormant at lower temperatures, with a reduction in respiration, the radish seeds became more active, suggesting that their optimal temperature for germination is relatively cold. The dormant, non-germinated radish seeds respirated less, with only 0.20 ppm per second, evincing their decreased metabolic activity. The change in CO2 per second with glass beads instead of seeds was -.02 ppm, a very minor change that may have been due to a small inaccuracy of the CO2 sensor or the movement of the CO2 molecules within the bottle, as the amount of CO2 would not expect to change without an organism present. The experiment did not seem to have any other glaring errors. However, if done again, a better method for removing the seeds from the cold water might save time and prevent any possible damage or stress to the seeds during handling. It also may have been prudent to use objects more similar to the radish seeds in size than the glass beads to prevent the differences in pressure from affecting the CO2 reading. The radish seeds were originally expected to respirate less at low temperatures, as most seeds become dormant when the temperature cools during the winter, but some types of seeds do grow better in the cooler months. The rest of the results followed the predictions.

Conclusion

 In this lab, it was found that germinated seeds respirate and produce CO2 at a greater rate than ungerminated seeds, and that germinated radish seeds respirate more at cool temperatures. From this, we can conclude that radish seeds have an optimal temperature for growth of less than 22 degrees Celsius.

References

Our wonderful Pearson AP Biology book :)