Date: _________________________
Name: __________________
Lab Bench – Cell Respiration Internet Tutorial
Preparation for Respiration Lab
Go to the following website: http://www.phschool.com/science/biology_place/labbench/lab5/concepts.html
Introduction
What are some processes in plants that require ATP? ______________________________________________________
Design of the Experiment
How can the rate of cellular respiration be measured? When you study the equation for cellular respiration, you
will see that there are at least three ways:
1. Measure the amount of ________________ consumed.
2. Measure the amount of ________________ consumed.
3. Measure the amount of ________________ produced.
In this experiment, we are going to measure the amount of _______________ consumed.
Features and Functions of a Respirometer
This illustration shows you the basic features of a ___________________________. It will measure changes in
gas ____________________ related to the consumption of oxygen.
You can construct a respirometer by putting any small organism in a vial with a pipette attached. This example
uses a cricket; in the laboratory experiment, you will use ____________. Remember, cellular respiration occurs
in the cells of both animals and ________________!
How the Respirometer Works
As O2 is used up, the pressure of gases inside the respirometer ______________. This causes water to
______________ the pipette.
The CO2 that is produced combines with KOH to form a ________________ precipitate, K2CO3.
Notice that as the gas volume inside the vial ____________________, the pressure of water outside the vial
forces water ________________ the pipette. Because the amount of water that enters the pipette is directly
proportional to the amount of oxygen consumed by the cricket, measuring the water volume in the pipette
allows you to measure the rate of __________________________.
How to Read a Pipette
Water in a pipette adheres to the side of the tube and forms a curved surface called a _________________. By
common practice, all readings are made at the bottom of the meniscus. The units for this pipette are milliliters
(ml).
The reading for the pipette illustrated here is??? ____________________
Assembling the Respirometer
In this experiment you will compare the rate of respiration in peas that are germinating to the rate in peas that
are dormant (dry peas). You will make the comparison at two different temperatures: 10°C and 25°C. In
addition, you will compare these rates to a ____________________________ control.
KOH is ________________! You must wear ___________________________ when using it.
More Information on Germinating Peas
It is important to know that nongerminating seeds are not dead; they are _____________________. Do they
respire?
Measuring the Rate of Respiration
Gas volume is related to the temperature of the gas. According to the gas law (V=nRT/P) , a change in
temperature will cause a direct change in volume. Because the temperature in the respirometers may vary
during the course of the experiment, you must correct for differences in volume that are due to temperature
fluctuation rather than rate of respiration. To do this, ____________________ any difference in the movement
of water into the vial with glass beads from the experimental vials held at the same temperature. Record the
result as the corrected difference.
Analysis of Results I
What would be the rate of oxygen consumption if the respirometer readings were as shown here? ______________
Lab Quiz (write answers in here for multiple choice)
1. _______
2. _______
3. _______
4. _______
Lab Quiz
1. Which of the following is a true statement based on the data?
a.
The amount of oxygen consumed by germinating corn at 22°C is approximately twice the amount of
oxygen consumed by germinating corn at 12°C.
b.
The rate of oxygen consumption is the same in both germinating and nongerminating corn during the
initial time period from 0 to 5 minutes.
c.
d.
e.
The rate of oxygen consumption in the germinating corn at 12°C at 10 minutes is 0.4 ml O2/minute.
The rate of oxygen consumption is higher for nongerminating corn at 12°C than at 22°C.
If the experiment were run for 30 minutes, the rate of oxygen consumption would decrease.
Answer – a
Study the graph carefully to see that at 10 minutes the 22°C germinating corn consumed 0.8ml of oxygen, while the 12°C
germinating corn consumed 0.04 ml of oxygen.
2. What is the rate of oxygen consumption in germinating corn at 12°C?
a.
b.
c.
d.
e.
0.08 ml/min
0.04 ml/min
0.8 ml/min
0.8 ml/min
1.00 ml/min
Answer – b
To calculate this, it is easiest to find the change in y at 10 minutes (0.4 ml - 0 ml = 0.4) and divided by the change in x (10
minutes - 0 minutes = 10 minutes). 0.4 ml/10 minutes = 0.04 ml/min.
3. Which of the following conclusions is supported by the data?
a.
The rate of respiration is higher in nongerminating seeds than in germinating seeds.
b.
Nongerminating peas are not alive, and show no difference in rate of respiration at different
temperatures.
c.
The rate of respiration in the germinating seeds would have been higher if the experiment were
conducted in sunlight.
d.
The rate of respiration increases as the temperature increases in both germinating and nongerminating
seeds.
e.
The amount of oxygen consumed could be increased if pea seeds were substituted for corn seeds.
Answer – d
This is the only statement that is supported by information provided on the graph.
4. What is the role of KOH in this experiment?
a.
b.
c.
d.
e.
It serves as an electron donor to promote cellular respiration.
As KOH breaks down, the oxygen needed for cellular respiration is released.
It serves as a temporary energy source for the respiring organism.
It binds with carbon dioxide to form a solid, preventing CO2 production from affecting gas volume.
Its attraction for water will cause water to enter the respirometer.
Answer – d
As carbon dioxide is released, it is removed from the air in the vial by this precipitation. Since oxygen is being consumed
during cellular respiration, the total gas volume in the vial decreases. This causes pressure to decrease inside the vial,
and water begins to enter the pipette.