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Investigation 6 - cellular respiration

AP Bio

AP Bio

on 19 November 2012

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Transcript of Investigation 6 - cellular respiration

Conclusion Errors and Improvements 1. Obtain a black tub and fill with water, either at 10 degrees C or room temperature(22C).
2. Open the three microrespirometers and put a cotton ball covered in KOH at the bottom of each using tweezers. Put non absorbent cotton on top of the KOH soaked one.
3. Fill a graduated cylinder with 50 Ml of water, and drop 25 germinating peas inside and measure the water displacement. the water displacement will be the volume of solid to use, which must be held constant. Do the same for the solid peas and glass beads ensuring that they all have the same volume. For the crickets make sure that the total of them weigh 2 grams.
4. Once the solids are added to the three respirometers seal it with the rubber stopper/ pippette. Put a metal washer areound the pipette to help keep it submerged in the water.
5. Put a piece of masking tape on the black bin filled with water to act as a sling for the three respirometers. Place the respirometers in the bath with the pipettes lying on the masking tape, open to the air. Let them sit for 7 minutes to acclimate.
6. Once the 7 minutes are finished put a little drop of food coloring at the end of the pipette. Place a piece of white paper in the bottom of the bin, and then submerge the pipettes and let them sit on the bottom of the bath with the numbers visible.
7. Let the pipettes be for 3 minutes and then take the first reading.
8. Take readings every 3 minutes for 12 minutes.
9. Calculate the cumulative volume of o2 gas taken in over the 12 minutes by subtracting from the initial time zero volume.
10. Subtract living organisms from the glass beads to calculate cumulative volume difference. The corrected difference is calculated by subtracting the glass bead change (Ml O2 consumed) from the change in the dry, or non-germinating, peas. The purpose of the corrected difference is to factor out the factors that do not include respiration AKA the glass beads and just observe the steady and even rate of O2 consumption in the different organisms (peas and crickets). The average slope for all the seeds is 0.011 which means that for each minute, 0.011 mL of O2 are consumed by the seeds. For the student-designed cricket experiment in room temperature the slope is 0.0243 meaning that each minute, 0.0243 mL of O2 are consumed. Many errors could have occurred throughout the lab. In the student designed portion, if the crickets were excited they may have had an increase in respiration rates. The temperature of the baths may have fluctuated, the volume of peas, beads, KOH, and cotton may have varied from respirameter to respirameter which would throw off the results. It was somewhat difficult to read the measurements on the pipettes and there may have been errors due to incorrect data readings. Possibly a 10 C difference in water wasn't large enough. Methods The chemical formula for cellular respiration is

C6H12O6 + 6CO2(g) 6CO2(g) + 6H20 + energy.

A more specific formula for cellular respiration is:

C6H12O6 + 6CO2(g) 6CO2(g) + 6H20 + 686 kilocalories of energy
mole of glucose oxidized

The most important product in this formula is the energy that is created for the cells but carbon dioxide and water are also created. This free energy is used primarily to drive cellular processes. In the formula PV=nRT, 'P' stands for pressure of the gas, 'V' stands for the volume of the gas, 'n' stands for the number of molecules of the gas, 'R' is the gas constant, and 'T' stands for the temperature of the gas.

In this lab, the volume of oxygen gas consumed was measured to determine the rate of respiration. Besides respiration, two variables that could affect the respirameter measurements were temperature of the gas and air pressure.

Germinated seeds will have different respiration rates than dormant seeds because they have different metabolic rates. Germinating seeds require more energy because they are growing as opposed to dormant seeds which use a minimal amount of energy due to their inactivity. This is an adaptive value of dormancy in seeds. Seeds can remain dormant until conditions are suitable for the embryo to begin growing. The seed contains food for the embryo to start to grow until it is big enough to make its own food. Background The purpose of the potassium hydroxide, or KOH, in the respiration chambers is to absorb the CO2 emitted. This helps ensure that only the O2 consumption is measured and not O2 and CO2. It helps keep our data more accurate.

The purpose of having a respiration chamber that is filled with glass beads is to collect data for a control group. It is necessary to have a control group because we need to have data that we can compare. We need to be able to compare the data from the glass beads to the data from the germinating and non-germinating peas.
The purpose of equilibrium in the water baths is to make sure our data is accurate. The respiration chamber must soak in the water bath before data is collected to make sure that the contents of the respiration chamber are the same temperature as the water. This will ensure that the data we collect is accurate. Investigation 6 - Cellular Respiration PEAS!!! SEED EXPERIMENT

The effects of temperature on the Respiration Rates of Germinating Peas vs. Non-germinating peas

Purpose: To test whether germinating peas or non-germinating peas have a higher rate of respiration and to test how temperature affects this. Student Designed Experiment:

The Effects of temperature on the Respiration Rates of Crickets.

Purpose: To observe how temperature affects the respiration rates of crickets. . Slope Null Hypothesis
T-test The null hypothesis for the student- designed experiment was: If we vary the change in temperature, then there will be no change in consumption of oxygen and respiration rates. The t-test value for the student-designed cricket experiment in room temperature is 2.905 and the p-value is 0.0622. Because the p-value is not lower than .05, we cannot reject the null hypothesis nor prove our hypothesis. Germinating
Non-germinating Glass beads were used as the control because they are non-living and therefore, would not perform respiration ; this is also why the glass beads had little to no O2 consumption. The Germinating seeds had the greatest consumption of oxygen which also indicates that they had the highest rate of cellular respiration. This can be explained because germinating seeds are rapidly growing and developing which requires alot of energy. Although non-germinating seeds are in a state of dormancy, they still require energy to stay alive. This is why little observable Oxygen consumption was recorded for the non-germinating seeds. Varying temperatures of the water bath were tested to observe the rate of respiration in different environments. The peas in the cold water bath the greatest amount of oxygen consumption and respiration rates. In colder temperatures, the peas must work harder to maintain homeostasis. They need more energy and must increase the rate of cellular respiration in order to maintain a favorable temperature for survival. Student Designed Experiment Results Similar to the peas, the crickets in the cold water baths had a higher rate of respiration. Again, possibly the crickets in colder temperatures must work harder to maintain homeostasis. They need more energy and must increase the rate of cellular respiration in order to maintain a favorable temperature for survival. Enzymes are also believed to be a factor. All enzymes have a specific temperature in which they work most efficiently. Any temperature to high and they will denature and any temperature to low and the enzyme will function slowly. Possibly the enzymes that aid in respiration for the crickets function most efficiently at 10 C. Data
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