Today, we'll be studying cellular respiration by performing Lab 11
from Biology with Vernier, 4th Edition, part of our complete solution for Biology.
We'll be using germinated peas that were prepared yesterday by soaking a handful
of peas in some water in a beaker and being allowed to sit overnight.
They'll start to germinate and then begin going through cellular respiration and
produce CO2 as they use up oxygen. To measure that, we're going to use our
Go Direct CO2 Gas Sensor. And then once we have graphical
analysis launched, we need to power on our Go Direct sensor.
So, we're going to push the power button and then you'll see a light begin
to flash red. Flashing red means that the sensor is on but it's not connected yet
to the software via Bluetooth. So, in Graphical Analysis,
we're going to click or tap on Sensor Data Collection to bring up the menu of sensors
that are available. If you check the backside of your sensor,
you'll see a little serial number. That number will tell you which sensor is
yours in the menu. We're going to find our sensor in the list and click or tap
Connect for that sensor. And then you should notice that the light
changes from red to a flashing green when it's connected to Bluetooth.
We can click or tap Done to close out that menu. And now, we're ready to prepare
our peas. So, that sensor can wait while we get our respiration chamber ready.
Our chamber is a 250 milliliter Nalgene bottle that we're going to use.
I've counted out already 25 germinated peas. We're going to gently pour those
into the neck of the bottle. And then, we're going to insert the sensor into the
neck of the bottle, just firmly enough to make a solid connection. And then,
the lab manual shows that the normal position is upright for this preparation
but you could also use the CO2 Gas Sensor laying down. CO2 is a fairly heavy
molecule so it has a tendency to sink to the bottom of the bottle. So, sometimes,
you get a little bit faster of a response if you reposition it in a
sideways position. The one thing that we need to do to get ready is change the
duration of time for our data collection. The default for this sensor is
600 seconds. We don't need quite that much time. So, we're going to click or tap
on Mode to bring up the time menu. And then, we're going to change the
duration from 600 seconds to 300 seconds. Click or tap Done.
Now, we're ready to begin data collection. Click or tap the Collect button and we'll
start measuring CO2 levels. All right. Data collection has completed.
And you'll notice that after data collection finishes,
the graph will autoscale for you. For some data analysis,
we'll go down and click or tap Graph Tools, and then select Apply Curve Fit
from the menu. This will select all of the data in our graph. We're going to apply a
linear fit which will give us an equation that includes slope.
The slope of our line is the respiration rate of our peas. That's important
once you've completed a run of data to properly clean out your chamber and also
to air out your sensor. The CO2 sensor can collect CO2 gas
within the barrel of the sensor. So, it should be fanned for at least a full
minute with a notebook or a stiff piece of paper in-between runs.
To prepare for another run, it's important to clean out the
respiration chamber. After dumping out the peas,
we recommend filling the bottle with water, dumping it out,
and then drying it completely with the paper towel in order to be ready for the
next run. For more information about this lab and others, and our complete solution
for Biology, please see our website.