Cellular Respiration Lab

Purpose: 

In this lab, we wanted to test the whether germinated seeds and non-germinated seeds would respire, and if so, the rate at which they do so.  Also, we wanted to see how temperature impacted rate of respiration as well.  

Introduction: 

Cellular respiration is the process in which organic molecules are broken down in order to create energy for an organism.  Cell respiration occurs aerobically, which mean that oxygen is necessary for the process to occur.  Cell respiration also occurs in the mitochondria.  Before respiration begins  glucose is broken down into two molecules of pyruvate in a process called glycolosis.  If oxygen is present, then respiration will occur next.  But if oxygen isn't present, fermentation will occur.  When oxygen is present, the two pyruvate molecules are converted to AcetylCoA, which is a coenzyme.  One molecule of CO2 is released in this stage.  Next, the citric acid cycle (or Kreb's cycle) occurs.  In this stage of respiration,  2 molecules of CO2 are released as a byproduct of the breakdown of pyruvate. Two pyruvates are present, so each molecule creates one ATP and 2 molecules of CO2.  Next, the pyruvates undergo oxidative phosphorylation.  In this stage, the electrons carried by NADH (NADH collects extra electrons from molecules throughout respiration) we released onto the electron transport chain, and are subsequently carried down to increasingly more electronegative molecules.  The spillover of extra electrons in this stage fuels the transport of H+ ions across the membrane of the mitochondria, creating a large difference in energy.  When the H+ ions travel across the membrane to once again, Chemiosmosis happens.  The movement of H+ ions across the membrane to a lower concentration create energy for the synthesis of ATP.  32 to 34 ATP are created in this stage.  Overall, 2 ATP are created during glycolosis, 2 ATP are created during the citric acid cycle, and 32 to 34 ATP are created during oxidative phosphorylation.  A way to see if respiration occurs is to monitor the output of CO2 in organisms, because CO2 is emitted in both the conversion of pyruvate to AcetylCoA and the citric acid cycle.

Germination of seeds is the process in which seeds become active and able to grow.  This happens because seeds that are dehydrated intake water, and therefore, enzymes that need water to function are able to do so once again.  A germinated seed can have shoots coming off of it, and a non- germinated seed looks shriveled and water-less.

                                                 

                                                        Non-germinated seeds

                                               

                                                            Germinated seeds

Methods:
First, we collected germinated and non-germinated pea seeds.  In order to germinate the peas, we soaked them in water overnight.  Then weproceeded to test the level of CO2 emitted from several different seed types.  Here's how we did it:

Next, we separated 25 germinated, 25 non-germinated, and 25 glass beads (this was used for a control) into separate containers.

Second, we tested each of those materials for the presence of CO2 over a ten minute time span.

Third, we put the 25 germinated peas into ice-cold water for approximately ten minutes, in order of I test the affect of tempurature of germinated peas on levels of CO2 output.  We then tested the cold peas for presence of CO2 as well.

Lastly, we created graphs showing the CO2 output over ten minutes.

Data:

       

Graphs and Charts:

                                                          CO2 Release vs. Time Graph

    

Discussion: 

In this lab, we tested cellular respiration in different types of seeds. We did this by calculating the amount of CO2 emitted by the seeds, since CO2 is a product of cellular respiration. Our group tested peas that were germinated at room temperature, peas that were germinated in ice water, and dormant seeds. We also used glass balls as a control group. Our results showed that at 0.80 ppm/s, peas germinated at room temperature emitted the most carbon dioxide, showing that they have the highest rate of cellular respiration. The germinated peas in ice water had a lower rate, at 0.71 ppm/s, showing that cellular respirations is still occurring in lower temperatures, just at a lower rate. The dormant peas were drastically lower, with a rate of 0.15 ppm/s. Our control group of glass beads had a rate of 0.10 ppm/s, showing that a small amount of carbon dioxide could have been coming from other places, such as the water trapped in the bottle, it could've been leaking into the bottle, or it could have been trapped in the bottle from the previous test. Overall, our results showed that a germinated cell has a higher rate of cellular respiration than a non-germinated seed, as well as there is a direct relationship between temperature and respiration: as temperate goes up, so does respiration; as temperature goes down, so does respiration. 

Conclusion: From this experiment we can conclude that the non-germinated seeds do not respire, as shown by the very little amount of CO2 that was being given off by the non-germinated seeds. As for the germinated seeds we found that when the seeds were at room temperature that they respired at the highest rate.  The cold seeds had a lower amount of CO2 then the room temperature seeds. In summary when the temperature is higher the respiration of CO2 is higher than those of seeds in colder environments and that non-germinated seeds do not respire.

References: 

http://plantsinmotion.bio.indiana.edu/plantmotion/earlygrowth/germination/germ.html

Campbell Biology, 9th edition