Biology Lab Respiration

Objectives:

1. How a respirometer works in terms of the gas laws.

2. The general processes of metabolism in living organisms.

3. To calculate the rate of cell respiration from experimental data.

4. To relate gas production to respiration rate.

5. To test the effect of temperature on the rate of cell respiration in germinating seeds in a controlled experiment.

Hypothesis:

1. The rate of aerobic respiration will be the fastest in room temperature water verses the ice water bath.

2. The pressure will change more in the vial with seeds than the vial with glass beads.

Materials:

Thermometer

Respirometer

Room Temperature Bath

Ice Bath

Silicone

Peas

Glass Beads

Water

Graduated Cylinder

Tweezers

(KOH) = Potassium Hydroxide

Non-Absorbent Cotton

Absorbent Cotton

Masking Tape

Weights

Plastic Gloves

Paper Towel

Dropper

Procedure:

1. Take room temperature bath, 25 degrees Celsius, and an ice bath, 10 degrees Celsius.

2. Respirometer 1:Obtain a 100-mL graduated cylinder and fill with 50-mL of water. Put 15 germinating peas into the cylinder, and determine the amount of water that was displaced which will amount to the volume of the peas. Record the volume of the 15 germinating peas. Remove the peas from the graduated cylinder and place them on a paper towel.

3. Respirometer 3: Fill the graduated cylinder with 50-mL of water. Place the glass beads in until the volume is equivalent to the germinating peas. Remove the beads and place them on a paper towel.

4. Repeat steps 2 and 3 to set up respirometers 4 and 6, one of germinating peas and the other of glass beads, to place in the other bath.

5. To assemble the four respirometers, obtain four vials, which are made by attaching a stopper to a pipette. Place 1 absorbent cotton in the bottom of each vial, and with a dropper filled with KOH, saturate the cotton with 15% KOH. Make sure the respirometer vials are dry inside. Try not to get the KOH on the sides, but wear latex gloves to prevent contact. Place a small amount of non-absorbent cotton on top of the KOH-soaked absorbent cotton. IMPORTANT: keep the amounts of cotton and KOH the same for every respirometer.

6. Place the first set of germinating peas and beads in vials one and three. Place the second set of peas and beads in vials four and six. Insert the stopper fitted with the pipette on top of each vial. Place a weight collar at the end of every vial

7. Make a sling of masking tape attaching it to each side of the water baths to keep the pipettes out of the water for the first seven minutes, this is the equilibration period. Vials one and three should go in the room temperature bath, and vials three and four should go in the ice water bath.

8. After the period of seven minutes, immerse all 4 of the respirometers entirely in the water with the weights. Water will enter the pipettes and then stop, if the water continues to move into a pipette, there might be leaks in the respirometer. Make sure you can read the pipettes from the side you are looking from. They should not be shifted throughout the experiment. Keep your hands out of the water to make sure the temperature remains constant.

9. Allow the respirometers to equilibrate for three minutes or more and then record, to the nearest 0.01 mL, the initial position of water in each pipette (time 0). Check the temperature in both baths and record them in the table. Every 5 minutes for 20 minutes take readings of the water's position in each pipette, recording the data in the table.

Discussion:

Aerobic respiration is the release of energy from organic compounds in the cell's mitochondria. This process requires oxygen. This respiration lab will show how there is an increase of aerobic, or cellular respiration. I hypothesized that aerobic respiration would happen quicker in the room temperature water.

In this experiment, the vial with only the glass beads was the control. In the two baths, the amount of oxygen taken in for the glass beads remained about the same throughout the experiment because there was no respiration taking place since the beads were lifeless. The consumption of oxygen for the peas in the room temperature water bath occurred faster than the peas in the ice water bath. If the conditions for germination are right then the peas in the warm bath will have aerobic respiration occur faster. This was proven because there was more oxygen consumption in the pea vial that was in room temperature water. Because there was more oxygen consumed, aerobic respiration accomplished quicker. KOH was used to take out carbon dioxide by turning it into a solid yellow material. Now that the CO2 is completely gone the reading will be accurate. If the carbon dioxide was not completely removed then it would have messed up the reading with oxygen. If the vials were not sealed, water could have leaked into them causing another misreading.

Conclusion:

This lab was a total disaster due to the poor planning of the students and the attitude taken into the lab. This lab could have worked out and been a descent lab to work with but since people were goofing off and not paying attention to the time and readings most didn't care if they didn't get them they would either get the reading from another class or make it up. The good thing about this lab was that it was over two days and had the easy stuff the first day and the hard stuff the next. The Respiration lab would have gone great if the class could have had some class and calmed down, but overall the lab itself was great.