Monday, November 18, 2013

Cellular Respiration Lab

Purpose- The purpose of this experiment is to determine whether germinated or non-germinated seeds had a higher respiration.  We did this by determining the rate of respiration for the non-germinated seeds and then with the germinated seeds before and after having sat in cold water. We used temperature as variable to see if the results would differ.  We also tested glass beads to determine a control between the two.  This lab helped us to understand the process of respiration and what can potentially slow down this process.

Introduction- Cellular respiration is a multi- step metabolic process that produces energy by the oxidation of organic molecules. Humans and animals go though this process. This process is aerobic and anaerobic. Aerobic means it has oxygen and anaerobic means without oxygen. The reason it is anaerobic and aerobic is because one step is anaerobic and the other steps are aerobic.  The process starts with an organic molecule and oxygen and ends with carbon dioxide, water, and energy. An example of this is glucose going through cellular respiration C6H12O2 + 6O2 -> 6 CO2 + 6 H2O + Energy. This is also called a redox reaction. Redox reactions are the transferring of electrons. The name redox comes from a mixture of the 2 things happening in a redox reaction.  One substance in being reduced (gains electrons) and oxidation (losing an electron). The electrons are transferred with coenzymes. NAD+ is the oxidized state and NADH is the reduced state.  Cellular respiration  goes through 3 steps. The first step is glycolysis which is an anaerobic process. Glycolysis end products are 2 ATP and 2 NADH and 2 pyruvate. The 2 pyruvate are oxidized to become 2 acetyl CoA . The next step is called the Krebs or Citric Acid cycle. The Krebs cycle is named after the scientist who discovered it Hans Krebs. This cycle uses the 2 acetyl CoA. This means that this cycle is repeated. After the 2 times the end products are 6 NADH and 2 FAD2.The last step is oxidation phosphorylation it consists of the electron transport chain and chemiosmosis. The electron transport chamber helps gradually decreases the free energy. During this time H+ are being pumped across the membrane and it creates a H+ gradient. In chemiosmosis the flow of H+ helps power  ATP synthesis.Oxidation phosphorylation   creates 26- 28 ATP. After all the steps are complete  it should result in about 30-32 ATPs. In this experiment we will use these concepts to help us understand the CO2 release.

                                                        Glass beads 

                                                 Germinating barley seeds 
                                           Non germinating barley seeds 
                                               Cold germinating barley seeds 
             Germinating barley seeds 
                      Barley seeds

   CO2 chamber- calculated amount of CO2 being produced by seeds and glass beads. 

Methods- We picked out 25 glass beads and 25 barley seeds that were germinated and 25 seeds that were not germinated. The 25 glass beads were used for a control group. We then put 25 glass beads in the respiration chamber. We let the beads the glass beads sit for 10 minutes. After the ten minutes was up we started to take measurements of CO2, with a device that measures CO2 contents.  We recorded the data on our Vernier Lab quest . Next we performed the same steps from the glass beads to the germinating Barley seeds, non germinating barley seeds. Except the  germinating barley seeds that have been placed in a cold ice bath for ten minutes. 

Discussion- Germination causes a higher rate of respiration than the non-germinating peas. This is because a seed needs to have optimal conditions in order for it to germinate. These conditions are met through cellular respiration which provide the correct amount of energy for these reactions to occur. Non-germinating seeds are "dormant" and their energy is stored (this is why nuts and seeds have so many calories); therefore, they don't need as much energy to perform vital processes. The beads served as a control group because no cell respiration occurred. This allowed for certain factors such as pressure to be accounted for without having to directly control it.

Lower temperature slows down the respiration process. The rate at which a reaction occurs, increases with higher temperatures. The higher the temperature of a solution, the faster the molecules are moving in solution. There are more collisions between reacting molecules, and more of those collisions have the necessary kinetic energy required to break bonds and perform necessary function. Respiration is a chemical reaction that breaks down glucose into carbon dioxide and water, so it works in the same way. The higher the temperature, the more kinetic energy because of the molecules moving around, the more cellular respiration can occur.

Not maintaining a constant temperature in the water bath could have caused inaccurate results. Keeping the cold, germinating seeds at a constant temperature would've made the experiment more accurate. Putting the respiration chamber in an ice bath would be a good idea. 

Conclusion- We concluded from the lab that germinating peas that have been at room temperature or in a cold ice bath have a higher rate of cellular respiration. This is because when plants germinate, they are coming out of the seeds as sprouts and beginning to grow, thus needing to use up more oxygen. Seeds that are not germinating do not need as much oxygen because they are not beginning to grow. The germinating seeds that were placed in the cold ice bath had a slightly slower rate of cellular respiration than the germinating seeds at room temperature because the cold temperature slowed it down. The rate of respiration is faster in warmer temperatures. 

References- References-

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