AP Biology
Name _________________________________
Date START________ FINISH ________
Period _____
Score _____ Sign-Off _______
Lab Partner __________________ Table ___
Investigation 5: Photosynthesis
Big Idea 2: Cellular Processes: Energy and Communication
PRELAB: Be ready to answer the following questions: (any could be found on the written portion of
your exams)
1. What environmental variables might affect the net rate of photosynthesis? Why would they and how
would you predict they would effect it?
2. What feature or variables of the plant leaves might affect the net rate of photosynthesis? How and why?
3. Could the way you perform a procedure affect the outcome?
4. What other life processes affect the amount of product formed from photosynthesis?
BACKGROUND:
1. What are two ways to measure the rate of photosynthesis?
2. What will you be measuring in this investigation?
3. What cellular activity will counteract the affects of photosynthesis?
4. As a result, what will you ultimately measure in this investigation?
PROCEDURE: Floating Leaf Disk Technique, Introduction p. 63
Follow instructions, pay attention to special notations/questions below…
Step 1: A 2% solution would be: .6g of Baking Soda in 300ml of distilled water.
Step 5: Caution (d.) Pulling more than three times on the plunger will definitely damage the disks.
Step 7:
1. Could the intensity or distance from the light source impact your results? Why or why not?
2. Data tables/graphs: # of Floating Disks per Time: Label each axis before you start
With CO2
Time (mins)
Without CO2
Time (mins)
Steps 8-9: See below for explanation of 1/ET50 or Lab Book p. 68
1. What was the ET50 for “Cup with C02” ________ What is the 1/ET50? _____
2. What was the ET50 for “Cup without C02” ________ What is the 1/ET50? _____
3. Which cup had the highest rate of photosynthesis? __________________
Designing and Conducting Your Investigation:
Now it is your turn to design your own investigations. What are some factors you might consider?
~Light intensity: distance from light source
~Light color/covering on cups
~Temperature
~Bicarbonate (Baking Soda) Concentration
~Direction of incoming light
~pH of the solution
~Type of Leaf: Physical Characteristics
~Type of Leaf: # or Location of Stomata
~Type of Leaf: Color
Choose one variable (above or your own idea) and conduct your experiment as an assay. For example, one cup
10 cm from light source, another 20 cm from light source, 30 cm etc… With this data you will be able to create a
graph of the Rate of Photosynthesis using: your chosen variable (x-axis) vs 1/ET50 (y-axis, see p. 69). [You would
plot the inverse of the ET50 in order to create a more traditional direct relationship graph since a high ET50 means that photosynthesis took a long
time and a low ET50 indicates a more productive condition for photosynthesis.] I have some variables on the lab table but feel free
to bring in your own.
Again, you will do a lab write-up and you may do this write-up with a partner. It will be a one page typed paper that
will include the following:
1. Hypothesis
2. Procedures (you can include your materials with your procedures)
3. Data Tables/Graphs (as above) including the ET50 for each variable as well as the control.
4. Conclusions including and explaining any experimental error.
PLANNING:
1. Our team will investigate the variable of:
2. We predict that:
3. Rough Draft of Data Table: (Use this to record your data initially and use as resource when you type up
your paper. You will graph the rate of photosynthesis as well.)
Independent
Variable:
(x-axis)
Total
# of
Disks
# of Floating Disks per Minute
1
2
3
4
5
Estimated Time
6
7
8
9
10
11
12
13
14
15
ET50
1/ET50
(y-axis)