30
as Producers
C6H12O6
C6H12O6
Name _____________
Teacher ______________ Hour ____
31
Unit 3 – Plants
By the end of this unit, you should:
KNOW:

















Vocabulary words for Quiz #1
Root (21.3)
Root Hairs (21.3)
Stem (21.3)
Blade (21.4)
Petiole (21.4)
*Chloroplast (4.2)
*Chlorophyll (4.2)
Pigment (in packet)
Absorbance (in packet)
Transmittance (in packet)
*Photosynthesis (4.2)
Reactant
Product
Glucose (sugar) C6H12O6
O2
CO2
H2O (water)












Vocabulary words for Quiz #2
Electron
Ion
Enzyme
Electron Transport Chain (4.3)
ATP Synthase (4.3)
Calvin Cycle (4.3)
ATP
NADPH
Photosystem I
Photosystem II
Thylakoid
Stroma
Words that are underlined and have a star* are key vocabulary words. These are the most important vocabulary words to know!
After the vocab quiz, circle what you didn‘t get correct on the vocab quiz
UNDERSTAND:
1. Understand the relationship between pigments and light absorption/transmittance.
2. Understand the importance of plants and photosynthesis to the structure of an ecosystem (the plants‘ role as the base
for all other life on earth).
DO:
Goal
1) Contrast the cellular structures of plant and animal cells.
2) Construct the equation for photosynthesis
3) Classify reactants and products in the photosynthesis
equation.
4) Describe the two main steps of photosynthesis:
a) Light Dependent Reaction
1. Step 1: Capture light energy
2. Step 2: Convert light energy into chemical energy
b) Light Independent Reaction
3. Step 3: Convert chemical energy into glucose
(food)
5) Explain the importance of photosynthesis in an ecosystem.
6) Write and perform an experiment that includes a hypothesis,
procedure, data, and conclusion.
7) Identify which wavelengths of light are absorbed/transmitted
by looking at a graph.
8) Identify which colors of light are absorbed/transmitted by
looking at a graph.
9) Translate information to and from double y-axis line graph
using 3 variables.
10) Identify a control in an experiment
Progress on Goal
What do I still need to study?
32
11) Identify similarities and differences between experiments
(S.20.4)
12) Predict the results of an additional trial or measurement in
an experiment (S.24.3)
13) Identify key issues or assumptions in a model (E.20.2)
14) Interpolate between data points in a table or graph (I.24.3)
15) Compare or combine data from two or more simple
presentations. (I.24.2)
16) Analyze given information when presented with new, simple
information (I.24.6)
17) Identify strengths and weaknesses in one or more models
(E.24.3)
33
Pin the Structure on the Plant!
Okay, you‘re not really going to ‗pin‘ anything, but do you know the main structures of a plant? Your task is to place
all of the plant structures in the correct place! Refer to your book on pages 648-652.
Step 1:
All of the words listed in ‗Bank #1‘ need to be drawn onto the bare stem below.
Step 2:
Once you have drawn all of the structures onto the plant, match each structure with its function from Bank #2.
*Use the ‗stem‘ as an example of how your labels should look.
Bank #1
Bank #2
Root Hairs
Blade
Petiole
Stem (shoot)
Root
A. Connects the stem to the blade.
B. Greatly increases the surface area of the root, allowing for more absorption
of water and minerals.
C. The broad, flat part of the leaf, used for collecting sunlight.
D. Anchor plants in the soil while absorbing, transporting, and storing
nutrients.
E. Supports the plant and transports materials throughout.
Stem
(E)
34
How do Plants use the Sun’s Energy?
Part I
Previously you have learned about how light from the sun carries energy in the form of waves, but how does a plant
use this sunlight to make it‘s own food? What type of food does a plant make? Is there anything else that a plant
produces while making food? What else do plants need besides sunlight in order to make food? Use the space
below to answer these questions to the best of your ability:
1) What does a plant need in order to survive? List as many things you can think of:
a. _______________________
b. _______________________
c. _______________________
d. _______________________
2) What type of food does a plant make? ______________________________
3) Does the plant make any other products besides food? If so, what? _________________________
4) What is this process called? _______________________________
STOP
Part II
Now that you have figured out what is used and what is made during this process, perhaps you can arrange these
components in a way that can be accurate, but easy to read. Scientists use a convention called a chemical
equation to do exactly this. Just like in mathematical equations, two or more things are added together to make a
product. Whenever a chemical reaction occurs (like in photosynthesis) there are:
1. Things that are used up in the reaction, called reactants
2. Things that are made, called products
Scientists use an arrow to represent that a chemical change has taken place. Look at the example below that shows
the production of table salt from the elements sodium and chloride:
Sodium +
Chlorine  Sodium Chloride
Reactants
=
Product
Your Turn:
In groups, use the cards provided to you by your teacher to create a chemical equation that best represents
photosynthesis. Record your results below:
After class discussion, write the discussed PHOTOSYNTHESIS equation below:
35
A History of Photosynthesis
How do we know so much about this process?
Before we can look at the history of our understanding of this process, we need to really understand what its name
means. As with so many words in biology, Photosynthesis is a word that has two smaller root words.
PHOTO – SYNTHESIS
Definition:
_____________________________________________________________________________________________
_____________________________________________________________________________________________
Two scientists discuss their theories on the source of a plant‘s food.
Scientist 1 - Aristotle
Plants obtain all necessary food from the soil. Matter must be conserved (cannot be destroyed or lost), and the
matter added to a plant when it grows must come from somewhere. The only matter into which the plant‘s roots come
in contact is soil. Thus, all the plant‘s food must come from the soil.
Scientist 2 - Jean Baptiste van Helmont
Plants do not obtain their food from the soil. An experiment has been performed in which a plant grew for five years in
soil. The soil was covered to prevent loss of material, and the only thing added to the container was water. During
these five years, the plant‘s weight increased by 164 pounds, while the weight of the soil remained constant. This
shows that a plant‘s food does not come solely from the soil.
1) Which of the following is a weakness of Scientist 1‘s argument? (E.24.3)*
A) Scientist 1 does not address the source of a plant‘s food.
B) Scientist 1 does not use data to support his argument.
C) Scientist 1 does not address the source of water for the plant.
D) Scientist 1 does not describe how the soil is converted into plant matter.
2) Which of the following assumptions is essential to Scientist 2‘s argument? (E.20.2)
A) The matter added to a plant must come directly through the plant‘s roots.
B) If the weight of the soil in which the plant grows remains constant, the plant must not be obtaining its
food from the soil.
C) Despite the cover, soil might be lost from the container.
D) A material other than water must be converted into plant matter.
36
Read the following passages about the major contributors to the study and understanding of photosynthesis
PART 1 – Food for Plants
Aristotle
Aristotle and his followers (back in 500 BC) were perhaps the first to make and record any
observations about plant growth. They made the observation that the life processes of animals
were dependent on plants. But the question remained…where do plants get their food? Based on
their observations, Aristotle and his followers came to the conclusion that plants got all of their
necessary food directly from the soil. Somehow, the plants just sucked up all of their food from the
dirt! Aristotle‘s theory was accepted up until 400 years ago.
1. What is the main idea of this passage? (I.16.3) Write it here:
______________________________________________________________________________________
______________________________________________________________________________________
Jean Baptiste van Helmont
In 1620, a Belgian scientist named Jean Baptiste van Helmont decided to
do an experiment to test Aristotle‘s theory. Van Helmont‘s experiment
was the first quantitative plant growth experiment to be done that resulted
in using precise measurements of mass, volume, etc to reach a
conclusion about photosynthesis. Van Helmont wrote:
“I took an earthenware pot, placed in it 200 pounds of earth dried in an oven, soaked this with water,
and planted in it a willow shoot weighing 5 pounds. After five years had passed, the tree that had grown
weighed 169 pounds and 3 ounces. The earthenware pot was constantly wet only with rain or (when
necessary) distilled water (distilled water is purified water that contains no particles or other chemicals)
To prevent dust from flying around from mixing with the earth, the rim of the pot was kept covered with
an iron plate coated with tin and pierced with many holes. Finally, I again dried the earth of the pot,
and it was found to be the same 200 pounds minus about 2 ounces.”
2. Why did van Helmont decide to do an experiment on plants?
______________________________________________________________________
3. Fill in the table below with the information from van Helmont‘s experiment.
Results
Tree
Soil
Initial weight
Final Weight
after 5 years
Difference in
weight
Loss or gain?
37
4. What do you think happened to the lost ounces of soil from Van Helmont‘s experiment?
_____________________________________________________________________________________
5. Why do you think it was important for van Helmont to use only dry soil in his measurements? (S.16.1)
______________________________________________________________________________________
6. Which statement below describes what van Helmont would conclude about the soil‘s role in providing food
for a plant? (E.20.1)
A. Soil is the only thing that provides food for the plant.
B. Water does not provide food to the plant.
C. If the soil lost no mass, but the tree gained mass, then something other than soil must provided food
to the plant. Water must be the thing that provides food to the plant.
D. Plant pots with rims inhibit the loss of soil, therefore, soil must be the main source of a plant‘s food.
7. Does this conclusion support or refute Aristotle‘s original conclusion? (E.24.4)_________________________
Part 2 – More than just water
Van Helmont‘s experiment was fairly elegant (simple) and provided a conclusive result—that water alone made
plants grow. He did not, however, consider what role the air had in plant growth.
Joseph Priestly
Near the end of the eighteenth century (1772) another scientist named Joseph Priestly began
making observations about plant growth. Priestly‘s experiment consisted of placing a lit
candle under a bell jar so that it was air-tight. Once the candle went out, it could not be lit
again. Without lifting the bell jar, Priestly tried to relight the candle by directing the sun‘s
beams through a magnifying glass. Priestly then tried the experiment again, but this time, he
placed a sprig of a green plant under the bell jar with the candle. Again, the candle burned out, and could not be lit
again. However, he noticed that after a few days, the candle could once again be lit.
He noted, ―I have accidentally hit upon a method of restoring air that had been injured by the burning of candles…at
least one of the restoratives that nature employs…is vegetation.‖ Priestly concluded that plants recycled the air to
keep it clean and pure. His proposed idea for that process worked like this:
“bad” air
(candle won’t light)
plants
“good” air
(candle will light)
38
8. Use your prior knowledge! Why did the candle in Priestly‘s first bell jar go out? What is necessary for all
flames to stay lit?
______________________________________________________________________________________
Jan Ingenhousz
Unfortunately for Priestly, neither he nor others could repeat the experiment and get the
same results. Therefore his theory had lost the impact that it first had. A few years later
though, in 1779, a Dutch physician name Jan Ingenhousz tried to repeat Priestly‘s
experiment. For the first time in many years, he was able to show results that supported
Priestly‘s work. Ingenhousz made one very important discovery in his experimentation:
The process of ―purifying‖ the air could only occur when there was light in the room. So
by adding to Priestly‘s original idea, the equation for this process would look like this:
“bad” air
(candle won’t light)
plants
LIGHT
“good” air
(candle will light)
With help from the growing field of chemistry, it was learned that the ―bad‖ air was carbon dioxide (CO 2). The ―pure‖
air was oxygen (O2). By applying this new information to the equation above, the new equation becomes:
plants
CO2
light
O2
9. Although Priestly and Ingenhousz‘s experiments were essentially the same, there was one essential
difference. What is the main difference between these experiments? (I.24.6)*
______________________________________________________________________________________
______________________________________________________________________________________
10. Based on this information, why do you think that other scientists could not replicate (copy) Priestly‘s
experiment?
______________________________________________________________________________________
______________________________________________________________________________________
From this, Ingenhousz went one step further in his quest to explain and understand photosynthesis. In 1796, he had
an idea that plants were doing something other than just ‗purifying‘ the air we breathe. Ingenhousz wondered if
plants could somehow also be getting the food that they needed through this process as well. He thought that
sunlight was used to split the CO2 into carbon and oxygen. He believed that the plant somehow then used the
carbon to make their food and then got rid of the O2. If we put these ideas into the equation of photosynthesis, it
becomes:
plants
CO2
FOOD +
light
O2 (oxygen)
39
11. According to Ingenhousz‘s hypothesis, what is the role of sunlight in photosynthesis?
______________________________________________________________________________________
Nicholas Theodor de Sassure
In 1804, a Swiss scientist names Nicholas Theodore de Sassure showed through careful
experimentation that water (H2O) was an essential part of the process of photosynthesis. He
remembered Von Helmont‘s experiment that showed plant growth with the addition of only water to
a potted willow tree. He knew that as a plant photosynthesized, it grew and increased in mass. De
Sassure concluded that the increase in mass was more than would amount from the intake of CO2
alone. He believed that once the CO2 was split, the carbon combined with the H2O to form the
plant‘s food. Therefore the new and improved equation for photosynthesis looked like:
plants
CO2 + H2O
FOOD (CH2O)
light
(containing C and H)
O2
+
(released into the atmosphere)
12. How is de Sassure‘s view of water different than Van Helmont‘s view of water? (S.20.4)
______________________________________________________________________________________
______________________________________________________________________________________
C.B. van Niel
The above equation for photosynthesis looks like it may be complete, but C.B. van Niel
(a graduate student at Stanford) discovered that it was not quite finished. In his studies,
he found that the O2 that plants released into the atmosphere did not come from the
CO2 being broken into carbon and oxygen. Instead the CO2 stayed together and the O2
came from the splitting of H2O into hydrogen (H2) and oxygen (O2).
13. C.B. van Niel helped to show that the oxygen that plants release come from the breakdown of water into
hydrogen and oxygen. Where did people originally think this oxygen came from? (S.20.4)
______________________________________________________________________________________
______________________________________________________________________________________
Please answer the following reading question:
14. Describe how the ideas of Aristotle are different from how we think of photosynthesis today. (E.24.4)
40
Germination, the initial growth of a seed, affects the yields
(amount of product) farmers can obtain from their crops.
Several factors are known to affect germination. The
following experiments were conducted to determine the
factors that influence the rate and amount of germination in
corn.
1. Which of the following factors did the researcher vary in
Experiment 1? (S.20.2)
A. Sample size
B. Type of seeds
C. Hormone treatment
D. Incubation temperature
Experiment 1
2. Based on these experiments, which of the following
practices would one most likely recommend to farmers
who want to increase the germination of their corn?
(I.24.2)*
A. Planting germinated seeds only
B. Planting when the soil temperature is
between 5° and 20°C
C. Planting when the soil temperature is
between 20° and 35° C
D. Planting when the soil temperature is
between 35° and 50°C
Four samples of 100 corn seeds each were placed on
moist filter paper in separate petri dishes. The petri dishes
were covered and the edges taped to prevent evaporation.
Each sample was incubated at a different temperature. The
germinated seeds were counted at 7, 14, and 21 days. The
results are presented in Table 1.
Sample
1
2
3
4
Temperature
(°C)
5
20
35
50
Table 1
Total Seeds Germinated
7 days
14 days
21 days
0
0
0
25
37
44
50
70
80
2
3
3
Experiment 2
One sample of 100 corn seeds was placed in a moist
petri dish, as described in Experiment 1. Another sample of
100 corn seeds was treated with a plant hormone prior to
being placed in a moist petri dish. Both samples were
incubated at 35° C. The germinated seeds were counted
over 7-day intervals as in Experiment 1. The results are
given in Table 2.
Untreated
Treated
Table 2
Total Seeds Germinated
7 days
14 days
21 days
48
65
79
65
75
82
Experiment 3
Samples of hormone-treated (HT) and untreated (U)
corn seeds were prepared as in Experiment 2. Four samples
of 100 seeds each were treated with hormones and
incubated at 5°, 20°, 35°, and 50° C, respectively. Four
more 100-seed samples were left untreated and incubated
at the same temperatures as the treated samples. The germinated seeds were counted over 7-day intervals. The
results are given in Table 3.
Temperature
(°C)
5
20
35
50
Table 3
Total Seeds Germinated
7 days
14 days
21 days
U
HT
U
HT
U
HT
0
28
52
2
0
35
67
3
0
39
65
3
0
43
76
3
0
44
80
3
0
45
82
3
3. Which of the following conclusions concerning the
germination of corn at 20°C and 35°C is consistent
with the results of Experiment 1? (E.20.1)
A. No seeds are able to germinate at
20°C or 35°C
B. About half as many seeds germinate
at 20°C as at 35°C
C. Twice as many seeds germinate at 20°C
as at 35°C
D. All the seeds germinate at 20°C and
35°C at the end of 21 days of incubation
4. On the basis of the experimental results, one could
generalize that as the germination period increases to
21 days, germination: (I.20.2)
A. decreases at temperatures below
5°C
B. increases at temperatures between
20° and 35°C
C. increases at all temperatures
D. decreases at all temperatures
5. Which of the following assumptions did the researchers
most likely make when selecting 35°C as the incubation
temperature for Experiment 2? (E.20.2)
A. Hormone activity would be inhibited at
35°C
B. The greatest number of corn seeds
would germinate at 35°C
C. The lowest number of corn seeds would
germinate at 35°C
D. Corn seed germination would not be
affected by temperature
41
6. Based on the information in Table 3, approximately how many seeds would one would expect to have
germinated at 10 days, with a temperature of 20°C? (I.24.3)*
A. 22
B. 37
C. 60
D. 90
7. If the researcher extended the observation
period to 28 days for seeds incubated at 5°
C in Experiment 3, the most likely outcome
would be that: (S.24.3)*
A. all of the treated and none of the
untreated seeds would germinate.
B. all of the untreated and treated
seeds would germinate.
C. approximately 50 of the untreated and
50 of the treated seeds would
germinate.
D. none of the treated and untreated
seeds would germinate.
E. Hormone-treated seeds germinate
faster
42
Photosynthesis, O2 and CO2
To start out our unit on photosynthesis, we will look at what plants are doing both in the light and in the dark. Today
you will see a set-up that includes a plant in an enclosed area and two sensors that measure O2 and CO2. Your
teacher will give you data that was gathered by the O2 and CO2 sensors throughout one day. Some of the data was
gathered when the plant was in the dark, and some while the plant was in the light under a box.
Use the space below to make a sketch of the set-up of the plant in both the light and in the dark. Then make
predictions about what trends you think you will see for the O2 and CO2 amounts measured from the plant.
Prediction for change in
CO2 levels in the dark
Plant in LIGHT
Plant in DARK
Prediction for change in
O2 levels in the dark
Prediction for change in
CO2 levels in the light
Prediction for change in
O2 levels in the light
Time of day
Plant data measured while in the dark under box
% O2
Parts per million (ppm) CO2
11:10
11:15
12:01
1:25
2:08
Time of day (pm)
2:12
2:30
3:15
4:13
4:30
5:50
6:20
Plant data measured while in the sunlight
% O2
Parts per million (ppm) CO2
43
Questions:
1. Refer to the data for the plant that was in the dark. Describe the trends that you observed in both CO2 and O2
levels for that plant.
Trend for actual CO2 data
Trend for actual O2 data
2. Refer to the data for the plant that was in the light. Describe the trends that you observed in both CO2 and O2
levels for that plant.
Trend for actual CO2 data
Trend for actual O2 data
3.
Based on these observations, explain what you think you could do to enhance the growth of plants and
explain why you think so.
Questions:
Below is a graph that displays CO2 and O2 levels while the plant was in the dark. Answer the questions for each
graph.
21
5000
2 0 .9
4900
2 0 .8
4800
2 0 .7
4700
2 0 .6
4600
2 0 .5
4500
2 0 .4
C a rb o n D io x id e ( p p m )
% o f O xyg en
O x y g e n a n d C a r b o n D io x id e le v e ls in t h e d a r k
% O2
P a r ts p e r m illio n
(p p m ) C O 2
4400
1 1 :1 0 1 1 :1 5 1 2 :0 1
1 :2 5
2 :0 8
T im e
4.
Describe the relationship between CO2 and O2 levels while the plant was in the dark. (I.24.4)
__________________________________________________________________________________
5.
What is the independent variable? (S.20.2) ________________________________________________
44
6.
Refer to the data for the plant that was in the light. Describe the trends that you observed in CO2 levels
for the plant while it was in the light. (I.16.4)
7.
Describe the trends that you observed in O2 levels for the plant while it was in the light. (I.16.4)
Graph the data for CO2 and O2 levels while the plant is in the light. Do this by following the directions for graphing a
double y-axis graph by following the instructions from your teacher. Answer the questions that follow.
8.
Compare your graph of CO2 levels in the light, to the graph of CO2 levels in the dark. What can you say
about them?
___________________________________________________________________________________
___________________________________________________________________________________
9.
Compare your graph of O2 levels in the light, to the graph of O2 levels in the dark. What can you say
about them?
___________________________________________________________________________________
___________________________________________________________________________________
45
Plant Cell Structures:
Why can plants do photosynthesis….but other things cannot?
Remember from our first unit that all living things are made of cells. Although this is a similarity amongst all living things, there
are many differences between these structures. Look at the lists below that compare plant and animal cells, and answer the
following questions.
Cellular Structure (organelle)
CYTOPLASM
MITOCHONDRIA
VACUOLE
GOLGI APPARATUS
CELL WALL
CELL MEMBRANE
LYSOSOME
NUCLEUS
CHLOROPLAST
ENDOPLASMIC RETICULUM
RIBOSOMES
Present in Plant Cell?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Present in Animal Cell?
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
No
Yes
Yes
Cell Membrane
Cell Membrane
Vacuoles
1. What cellular structures (organelles) do plant cells have that animal cells do not?
______________________________________________________________________________________________
______________________________________________________________________________
2. Read pages 103-104 in your book, and answer the following questions:
a. Which structure (organelle) is essential to a plant‘s ability to do photosynthesis? _______________
b. In a plant, where are these structures located?
c. What is chlorophyll, and what does it do?
d. Where can you find chlorophyll in the cell?
46
Light and Pigments
As you just learned, plant cells have
structures that animal cells do not.
These structures are called
chloroplasts. Chloroplasts are located
in the cytoplasm of the plant cell (see
diagram to the right). This structure, as
you also learned, contains a molecule (a
group of atoms) called chlorophyll.
Chlorophyll is a molecule that absorbs
light. We call light-absorbing molecules
pigments. Although the most common
plant pigment is chlorophyll, plants may
also contain other pigments that absorb
the sun‘s rays.
As we discussed earlier, energy from
the sun travels to the earth in the form of
waves. This energy varies in its
strength, from the warming rays of infrared to the damaging rays of ultraviolet (UV). Visible light is only a small fraction of the
total energy that comes from the sun. Visible light consists of a spectrum of colors. Each color has a different wavelength and
energy content (see the diagram below).
Sunlight, which is what our eyes perceive as
―white light‖, is actually a mixture of different
wavelengths of light. Many of these
wavelengths are visible to our eyes and
make up what is known as the visible
spectrum. Our brain interprets the different
wavelengths that travel through our eyes
and optic nerves as different colors.
Photosynthesis uses only certain
wavelengths, or colors, of visible light. The
green color of plants emphasizes that fact.
Not only does photosynthesis depend on
particular wavelengths of light, it also works
more or less efficiently depending on the
intensity of the light. The ideal intensity of
light varies for different plants. Of course, many factors, such as the availability of water and nutrients in the soil also affect
photosynthesis.
Answer the Questions on the following page:
47
1. What is a pigment?
2. What is the name of the main pigment found in plants?
3. In which cellular organelle is this pigment found?
4. Why do you think that chloroplasts are essential to a plant‘s ability to do photosynthesis?
48
Light and Pigments—How do they interact?
As you read earlier, pigments are compounds that absorb specific wavelengths of light. We also know that
photosynthesis depends upon the pigments that plants and algae contain. Today‘s demonstration will allow you to
see how various wavelengths of light are both
absorbed by and transmitted through
chlorophyll. To gather data today, we will be
using a device called a spectrophotometer. If
you break this word into smaller parts, you will
see that a spectrophotometer is a device that
measures information about a spectrum of light
waves.
http://www.gmi-inc.com/Genlab/spec_fig2%20diode%20array.gif
Procedure:
1.
Your teacher will show and explain to you how the spectrophotometer works.

Using a tube of white paper, start at 400 nanometers (nm) and increase by increments
of 30 nm up to 700 nm.

Block the passage of light through the cuvette well and adjust the spectrophotometer
to 0% transmittance.

Set the first wavelength to 400 nm.

Put the ―blank‖—a test tube of acetone— into the spectrophotometer and adjust to 0%
absorbance.

Place the sample tube containing chlorophyll dissolved in acetone into the cuvette well
and record both the absorbance and transmittance values.
Data Analysis:
Use the data in the table on the next page to answer the following questions and to create a graph in
Excel. The wavelength in nm should be placed on the x-axis. The absorbance and
transmittance should both be plotted on the y-axis. Remember to include a title and labels for
each axis!
49
Data Table:
Wavelength in
nanometers (nm)
Absorbance
Value
(Range 0-2)
Percent of wavelength
transmitted
(Range 0-100)
400
2
1
430
1.95
.75
460
1.95
1.5
490
1.6
8.5
520
1
35
550
.99
32.5
580
1.3
19.5
610
1.9
10.5
640
1.7
7
670
1.3
17
700
1.5
4
Questions:
Use your graph to answer these questions about the spectrophotometer data:
1. Using the table below, label the appropriate wavelengths on your Excel graph with their corresponding
colors. Please use colored pencil to do this.
Red
780 to 622 nm
Orange
622 to 597 nm
Yellow
597 to 577 nm
Green
577 to 492 nm
Blue
492 to 455 nm
Violet
455 to 390 nm
2. Which colors of light are absorbed the most by chlorophyll? (I.24.1)
3. Which colors of light are mostly transmitted by/through chlorophyll? (I.24.1)
4. According to the chart in question #1, which color(s) have the largest wavelength for visible light? (I.20.1)
5. According to the chart in question #1, which color(s) have the smallest wavelength for visible light? (I.20.1)
50
6. Look at the graph that you made. What appears to be the relationship between absorbance and
transmittance? (I.24.4)
A. There is no relationship between absorbance and transmittance
B. Absorbance and transmittance are opposite of one another. As absorbance of one color of light
increases, its transmittance decreases.
C. As transmittance of a color of light increases, so does its absorbance.
D. As transmittance of a color of light decreases, so does its absorbance.
7. What do you think is happening to light that is being transmitted—in other words, where is it going?
8. If you were going to grow plants and wanted to use the optimum wavelengths that their pigments absorb,
which wavelengths would you use? Refer to data from the data table to support your answer. (S.24.4)
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46
Absorbance and Transmittance of Light
Experiment I
Four identical cups and their covers were painted
white, red, yellow, and black, respectively. Each cup was
filled with the same amount of water and covered. The cups
were then placed in direct sun-light. The temperature of the
water, in degrees Celsius (°C) was recorded at the start of
the experiment and then every 5 minutes (min) for 40 min.
The data are shown in Table 1.
Table 1
Figure 3
Temperature (C)
Solar energy is energy that comes directly from
sunlight. The following experiments were performed to
study how solar energy is absorbed by different materials.
0
White
Cup
Red
Cup
Yellow
Cup
Black
Cup
0
25.5
25.5
25.5
25.5
5
26.0
26.0
25.8
26.5
10
26.5
26.5
26.5
27.5
15
27.0
27.0
27.0
29.0
20
27.2
28.0
27.5
30.0
25
27.5
28.2
28.0
31.0
30
28.0
29.0
28.5
32.0
35
28.5
29.5
29.0
33.0
40
29.0
30.0
29.5
34.0
Experiment 2
A clear glass tank was filled with water while in the
shade. A thermometer was placed in the water through a
small hole in the cover of the tank and the temperature was
recorded. Then the tank was placed in direct sunlight
(Figure 2) and the temperature was recorded every 5 min.
The data are shown in Figure 3.
Figure 2
221
10
0
15
0
Time (min)
20
0
25
0
30
0
1.
According to the information in Experiment 1,
in which of the following cups was the
temperature of the water highest after 20 min?
(I.13.1)
A. White
B. Red
C. Yellow
D. Black
2.
Which of the following best describes how
Experiment 1 differed from Experiment 2?
*(S.20.4)
A. In Experiment 1, colored water was
used; in Experiment 2, clear water
was used.
B. In Experiment 1, the color of the cups
was varied; in Experiment 2, a clear
tank was used.
C. In Experiment 1, the amount of water
in each cup was varied; in
Experiment 2, the same amount of
water was used in each step.
D. In Experiment 1, the cups were
placed in the sunlight; in Experiment
2, the cups were placed in the shade.
3.
Which of the following statements best
explains why the temperature of the water
increased in Experiment 2? (E.24.4)
A. The cup and the cover are both
painted white, which helps the water
to absorb solar energy.
B. Solar energy heats the water in the
glass tank as it is exposed to
sunlight.
C. The water in the tank cools as the air
around the tank gets hotter.
D. The tank absorbs solar energy from
the air around the tank.
Temperature (°C)
Time
(min)
5
51
47
4.
If, in Experiment 1, the temperature had been
measured in the red cup at 18 min, the most
likely value would have been: (I.24.3)
A. 26.5°C
B. 27.0°C
C. 27.5°C
D. 28.0°C
5.
Which of the following statements best
explains why the results of Experiment 1
support the conclusion that differently colored
cups absorb varying amounts of sunlight?
(E.20.1)
A. The water temperature did not
change in the white cup.
B. It took 40 min for the water in the
different cups to reach 29° C.
C. After 40 min, the water in each of the
cups was at a different temperature.
D. The longer the cup was in the
sunlight the warmer the water
became inside the cup.
47
52
Photosynthesis Concept Map
Word Bank
some may be used more
than once
CO2
chemical energy (ATP)
chlorophyll
chloroplasts
glucose (C6H12O6)
H2O
H2
light
light dependent stage
light independent stage
light energy
O2
into
contain
converts
takes
place
in
Photosynthes
is
is divided into
which
requires
and
forms
combined
with
chlorophyll
which
traps
and
splits
into
as a
is released as a
by-product
48
53
How are plants used by humans?
This may seem like a simple question with a simple answer. However, plants and their by-products are found in
more aspects of our life than we can even imagine! Below, please brainstorm and write down all of the ways in which
humans depend on, or use plants. Be specific in your answers.
Write your answers down under the column labeled ―Think‖. When you have written down as many answers as you
can, sit quietly until your teacher instructs you to discuss your answers with a partner. Write down any answers from
your partner that you did not have in your original list under the column titled ―Pair‖. We will then discuss these
answers as a class. Write any remaining answers (that you and your partner did not discuss under the column
labeled ―Share‖.
Think
Pair
Share
CATEGORIES of plant uses by/for humans  With the class, group your individual ideas into larger categories. Write them here:
Using complete sentences, answer questions 1-3 below.
10.
Of all the categories listed above, which do you think is the most important or essential use of plants by humans?
____________________________________________________________________________________________
11.
Why did you choose this as the most essential use of plants by humans? (ie: If humans were not able to have or
use plants in this manner, what would be the result for humans)?
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
12.
Do you think that plants ever depend on humans? __________ If so, how?
_____________________________________________________________________________________________________
_____________________________________________________________________________________________________
Look at your list of the ways in which humans use plants. List a few plant structures (parts of a plant) that are used for these
purposes.