Cellular Respiration Lab

Purpose: 

The main objective of this lab was to find out the rate of respiration in dormant seeds, seeds which were germinated, and seeds which were germinated and added to cold water. The temperature was the dependent variable as it was changed from room temperature to ice cold water. The environment, sensor and type of seed used remained the same, making it the independent variable. The main focus was to see the difference temperature makes in the respiration of germinated and non-germinated seeds.

Introduction:

Cellular respiration is a form of aerobic respiration in which glucose is broken down in in order to produce ATP. The general formula for cellular respiration is C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy. This process takes place in the mitochondria. Cellular respiration has 3 stages: glycolysis, citric acid cycle, and oxidative phosphorylation. At each of these stages, ATP is produced. During glycolysis, glucose is broken down into 2 pyruvate molecules. 2 ATP is required to phosphorylase glucose but 4 ATP are produced and 2 NADH. The pyruvate is then oxidized to acetly CoA and then goes on to the citric acid cycle. The citric acid cycle then produces 4 CO2  , 6NADH, 2FADH2 ,and 2 ATP. Finally, in oxidative phosphorylation, the electron transport chain and chemiosmosis are combined together. The total yield for a single molecule of glucose is 30-32 ATP.  Temperature affects the rate of respiration.

Methods:

25 similar pea seeds which were germinated had been counted and picked out along with 25 dormant seeds and 25 glass beads. The glass beads were used as a control group. We first tested the germinated seeds by simply putting them in a container covered with the respiration sensor. Then we had the germinated seeds sit in ice cold water and once again put them in the container covered with the sensor. The same thing was done with the dormant seeds to use as comparison. The glass beads were a control group to act against the dormant and germinated seeds. 

We used the Lab Quest to take all the CO2 measurements

The germinated seeds at room temperature

The cup of cold water that the seeds were to be put into

The seeds soaking in the Ice Water

Data:

The rate of respiration for all seeds

Graphs:

The CO2 Graph of the germinated seeds at room temperature

The CO2 Graph of the non-germinated seeds at room temperature

The CO2 Graph of the Germinated seeds after submerged in Ice water

 Combonation of all graphs 

Blue= Germinated at room temp

Purple= Germinated after submerged in ice-water

Green= non-germinated seeds

Red= Glass beads that served as constant

Discussion:

The rate of respiration for the peas at room temperature was .32 ppm/s. The rate of respiration for the peas at the cold temperature was .97 ppm/s. The rate of respiration for the non germinating peas was .05 ppm/s. The average rate of respiration for the peas was .446 ppm/s. The average rate of respiration for the glass beads was .015 ppm/s. The respiration rate was higher for the germinating peas when compared to the respiration rate for the non germinating peas. The temperature of the water also had an effect on the respiration rate of the peas. The peas that were in then cold water had a higher rate of respiration than the peas that were in the water at room temperature

Conclusion:

As shown in the graphs above it is obvious that the germinated seeds produce the most co2, but their co2 production rate decreases after they have been submerged in water. Also it should be noted that the non-germinated seeds barely produced more co2 than the glass beads. So it can be determined that the non-germinated seeds produce little or if not any co2.

 Reasources:

Campbell Biology Ninth Edition

Enzyme Catalysis Lab

Purpose: An enzyme is a protein which speeds up the reaction of a certain biological process. During this lab, the function of an enzyme was tested. Inhibition was also tested. An inhibitor slows down or stops a reaction completely.

Introduction: An enzyme is used to speed up a chemical reaction. This is called a catalyst. a catalyst is needed to raise the activation energy of a material. this material is called the substrate. the substrate will bind to the enzyme in order to activate the reaction and produce the final product. After the product is made the enzyme is not just thrown away or used up, it can be used over and over again, as long as there is substrate for it to act upon. But there are ways that the enzyme can break and fall apart, this is called Denaturing. Once an enzyme becomes denatured it cannot do its job and is therefore useless.  Two very common ways that enzymes become denatured is by a change in ph or a change in temperature. Enzymes like to live in very specific zones. they don't like it too hot or to cold. and if they are out of their comfort zone they will not work as well. and if they get too far out of their comfort zone they will not work at all. This is how enzymes get denatured. Enzymes can only work on a set number of substrates at a time. So if we were to say that one enzyme can only process one substrate every 3 minutes, then after 9 minutes 3 substrates would be made into products. And even if we have 100 substrates to choose from, after 9 minutes only 3 will be made into products. But if we were to add more enzymes into the mix more products can be made. So if there were 2 enzymes after 9 minutes they would have made 6 products, and so on and so forth. I think you get the idea.  Enzymes can only go so fast, and they can only continue  to work as long as there is substrate for them to work with.

Methods: In order to test the ability of an enzyme and an inhibitor, 7 cups were filled with H2O2. Each of these cups had a certain time range the catalase had to be left in there for, ranging from 10 seconds to 360. Catalase in the form of yeast was added in order to start the reaction, and sulfuric acid was added in order to stop the reaction. The solution was then titrated with potassium permanganate until the solution had turned a purple-brown. We knew the solution had ran out of H2O2 once the solution remained a solid purple-brown color.  

Data:

Graphs:

Discussion:

when we titrated for the baseline we found that there was consistently a 3mL reading for the baseline. Then when we found the percent that was spontaneously decomposed in 24 hours of sitting out, we found that there was a  43% difference in the amount that was decomposed. Then when we  titrated the solutions we noticed some interesting things. For instance, the amount of KMno4 that was consumed declined until the time before reaction was 90 sec; then once the tione hit 90 sec the amount consumed stayed the same for the rest of the experiment. this shows that after a min and a half there was no other effect on the amount of KMno4  that would be consumed. Then when we looked at the amount of H2O2 that was used it increased until 90 seconds and then it also leveled off. So It would seem that after 90 seconds the total production of the enzymes will level off.

Conclusion: The rate at which a 1.5% of H2O2 solution decomposes is .22ml of H2O2 per second. After 10 seconds, 2.2ml of the H2O2 was used. A maximum of 2.5 ml of H202 was used during the reaction. After 90 seconds, the H2O2 was no longer used up in the reaction.