- Living things need energy to carry on most of their processes. The cells of germinating seeds oxidize carbohydrates, in the process known as cellular respiration, to provide energy for growth. The balanced equation for cellular respiration (oxidation of glucose) is as follows:
C6H12O6 + 6 H2O + 6 O2 ---> energy + 6 CO2 + 12 H2O
- In this lab, you will observe the release of heat energy and the formation of carbon dioxide by germinating seeds.
MATERIALS:Gas collecting bottle
Three-holed rubber stopper (to fit bottle)
Thermometer
Thistle tube
Bent glass tube
Silicone grease or Vaseline
Rubber tubing
Pinch clamp
Can to hold bottle
Sawdust
Water (room temperature)
Pea seeds for sprouting
80-mL beaker
*Limewater* Here are instructions for making limewater if you do not have any.
PROCEDURE:
Setting-up the apparatus for observing heat energy of germinating seeds (see Figure 1 above).
1. Put some sawdust in the bottom of the can and place the bottle, centered in the can, on the sawdust. Add sawdust around the bottle and pack it down, adding more sawdust as necessary. The sawdust is your insolation for the apparatus, which is more accurately called a calorimeter.
2. Add the pea seeds to the bottle so that they fill about 1/4 to 1/3 of the bottle. Add room-temperature water to just cover the seeds.
3. Securely stopper the bottle and insert the Thermometer, Thistle tube, and glass tube as shown. Be careful not to break them. Using a small amount of silicone grease or Vaseline to lubricate them will help. The thistle tube must be inserted to just above the bottom so the water will seal out the outside air. The thermometer tip needs to be in the center of the seeds. It must seal with the hole in the stopper, but be able to be removed and replaced to check the temperature.
4. Attach the rubber tubbing and secure the pinch clamp at the end to seal the air inside. The tubing needs to be long enough to go into the 80-mL beaker with limewater later on in the experiment.
Observations.
5. Pull the thermometer up and read the temperature. Remember, always put your finger over the hole if you completely remove the thermometer, to keep the air inside the container from mixing with the outside air. Record your temperature.
Temperature at start of observation. ________ deg. C
6. Check the temperature as before at the end of the day. Record the temperature and the number of hours from the start.
Temperature ____ hours after start. ________ deg. C
7. After 24 hours, check and record the temperature as before.
Temperature after 24 hours. ________ deg. C
8. After 48 hours, check and record the temperature as before.
Temperature after 48 hours. ________ deg. C
Checking for carbon dioxide.- At the beginning of the lab, there was only a trace of carbon dioxide in the air trapped in your apparatus. As the cells of the seeds "burned" glucose to produce energy, they used-up the oxygen in the container, and gave off carbon dioxide as a byproduct. Limewater will react with carbon dioxide and turn milky.
9. Add some limewater to the 80-mL beaker and place it next to the can. Remove the pinch clamp from the rubber tubing and stick the tubing into the limewater as shown in figure 2.
10. Force the gas in the jar through the limewater by slowly pouring water into the thistle tube until the jar is filled. If the limewater turns milky, carbon dioxide is present.
What did you observe as the gas from the jar bubbled through the limewater?________________________________________________________________________
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From the data collected in your observations, what evidence was there that germinating peas are releasing energy?
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What gas was produced during the reaction? _________________
What are the products of the oxidation of carbohydrates?
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Why was the jar packed in sawdust?
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Back to Lab Dad's Laboratory
- In this lab, you will observe the release of heat energy and the formation of carbon dioxide by germinating seeds.
ENERGY RELEASE
AND
CELLULAR METABOLISM
INTRODUCTION: