# Cellular Respiration in Crickets

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```					                                                      Cellular Respiration in Crickets

Before reading this lab, go to www.biology.com. Once there select biology place  Lab Bench  Cellular Respiration.
Review each part of this lab activity including the lab quiz. Then review the procedure below.

Before doing this laboratory you should understand:
 how a respirometer works in terms of the gas laws
 the general processes of metabolism in living organisms.

After doing this laboratory you should be able to:
 calculate the rate of cell respiration from experimental data
 relate gas production to respiration rate
 test the effect of temperature on the rate of cell respiration in a living thing under different temperature conditions

Write the equation for cellular respiration in the space provided below. Circle the gas molecules in this equation.

In this experiment you will measure oxygen consumption in crickets at different temperatures. For every 6 molecules of
oxygen that are consumed, however, you will notice that there are 6 molecules of carbon dioxide that are produced.
Since you want to measure the change in the number of gas molecules in your respirometer due to cellular respiration,
you need to remove carbon dioxide gas from the system. In order to do this, you will add KOH to the cotton at the bottom
of each respirometer. KOH fixes carbon dioxide gas into K2CO3 molecules. This will allow you to measure oxygen
consumption in the respirometer.

Gas molecules follow specific laws called the gas laws. The ideal gas law equation is
PV = nRT
P = pressure of gas molecules
V = volume of gas molecules
n = number of molecules of gas
R = gas law constant
T = temperature

In this experiment Temperature and pressure will remain constant. The number of gas molecules should change as the
cricket consumes oxygen. When this happens the volume of gas particles will decrease and water will move into the
respirometer as space becomes available. The movement of water will directly measure mL of oxygen consumption.

Procedure:
1. Prepare a water bath at your assigned temperature
either 30 or 10 degrees Celsius.
2. Obtain two respirometers. Place a wad of absorbent
cotton in the bottom of each tube.
3. Add 2 mLs of 15% KOH to the cotton.
4. Place a piece of non-absorbent cotton over the top of
the soaked cotton so the crickets will not come in
contact with the basic KOH solution.
5. Obtain 2 crickets, and determine their mass, and place
them into one of the respirometers.
6. Place an equal mass of glass beads into the second
respirometer.
7. Place both respirometers in the water bath with the
pipette tip out of the water. Allow them to rest this way for 7 minutes.
8. After 7 minutes, drop your respirometers into the water baths and have your instructor add food coloring into the tip of
each respirometer. Allow them to calibrate for three more minutes.
9. After three minutes record the water level in each respirometer. This is your time 0 reading.
10. Continue to make recordings until 30 minutes have passed, and adjust the readings for the crickets with the glass
Before beginning the lab, Answer the following.

2. Predict measurable results based on your hypothesis.

3. Practice using the data table by completing the table below:

Title

(min)   Temp.
Initial (mL)    Final (mL)        Diff. (mL)*     Initial (mL)     Final (mL)         Diff (mL)   Adj. Diff. (mL)**
0                   .97                                               .92
5                                     .96                                              .85
10                                     .95                                              .81
15                                     .94                                              .75

*Volume difference = Initial Volume at Time 0 – Final Volume at Time X
**Adjusted Difference = Cricket Volume Difference at Time X – Glass bead Volume Difference at Time X (Keep your
algebraic sings, +, and -)
Note: The adjusted difference is the cumulative Oxygen consumption at Time

Title

(min)   Temp.
Initial       Final          Diff.     Initial      Final       Diff (mL)      Adj. Diff.
(mL)          (mL)          (mL)*      (mL)         (mL)                        (mL)**
0
2
4
6
8
10
12
*Volume difference = Initial Volume at Time 0 – Final Volume at Time X
**Adjusted Difference = Cricket Volume Difference at Time X – Glass bead Volume Difference at Time X (Keep your
algebraic sings, +, and -)
Note: The adjusted difference is the cumulative Oxygen consumption at Time x

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