Biology Schedule - Photosynthesis Unit
Wednesday Oct. 271: The Chemistry of Autumn Colors A reading and Study Guide
2. Why Study Photosynthesis?Assignment- Answer the following questions while reading the article
1. What is Photosynthesis?
2. Why is photosynthesis important in food production, energy production, as fiber and
other materials and the environment?
3. Why study photosynthesis?
4. What is the role of photosynthesis in agriculture, energy production, the environment,
electronics and medicine.- Due Thursday, Oct. 28
Friday -Oct. 29 - Notes on Photosynthesis /Photosynthesis video
Monday November 1 The Worldng Ce!l: Energy From Sunlight Internet Activity in
Library
Tuesday- November 2- Paper Chromatography Lab (Due Wednesday, Nov. 3)
Wednesday - November 3- Leaf diagram / photosynthesis drawings
Monday Nov 8- Electron Movement Lab Demonstration / prepare for leaf stomata lab
Tuesday - Nov. 9 -Leaf Stomata lab Due Thursday, Nov. 11
Wednesday - Nov. 10 Review
Thursday - Nov. 11 Test Photosynthesis Unit
Biology Study Guide - Photosynthesis
Test Date
Text Chapter 8
Online textbook activities and multiple choice questions
Labs Paper Chrom,atography
Leaf Stomata
WorksheetsReading the Chemistry of Autumn Colors and Why Study Photosynthesis?
Video on Photosynthesis
The Worldng Cell: Energy From Sunlight
Internet activity
leaf diagram
Photosynthesis reading
Lab demonstrations on electron movement
Lab demonstration: Energy Flow: Photosynthesis
1. Write out the simple chemical reaction for photosynthesis.
2. What are the reactants of the light dependent reaction? The products?
3, What are the reactants of the Calvin Cycle? The products?
4. What is the other name for the Calvin Cycle?
5. What is the role of NADPH in photosynthesis?
6. What is the role of ATP in photosynthesis?
7. Describe a photosystem.
8. Draw and label a chloroplast.
9. What happens in the thylakoids?
10. What happens in the stroma?
11. What happens when water splits?
12. Describe how a stomata works in a leaf.
14. Be able to label a leaf diagram.
15. Be able to calculate an Rf value.
16. What does paper chromatography do and why is this process useIul.
¯
Ternls:
¯
chloroplast
¯
chlorophyll
¯
stroma
¯
thylakoid
¯
light reactions
"
THE _HEM!b
- OF AUTUMN COLORS
Every autumn across the Northern Hemisphere: diminishing daylight hours and falling
temperatures induce trees to prepare for winter. In these preparations, they shed billions of tons of
leaves. In certain regions, such as our own, the shedding of leaves is preceded by a spectacular
color show. Formerly green leaves turn to brilliant shades of yellow, orange, and red. These color
changes are the result of transformations in leaf pigments.
The green pigment in leaves is chlorophyll. Chlorophyll absorbs rdd and bluelight from the
sunlight that falls on leaves. Therefore. the light reflected by the leaves is diminished in red and
blue and appears green. The molecules of chlorophyll are large (C55H70MgN406). They are not
soluble in the aqueous s’)lution that fills plant cells. Instead, they are attached to the membranes of
disc-like structures, called chloroplasts, inside the cells. Chloroplasts are the site of
photosynthesis, the process in which light energy is converted to chemical energy. In chloroplasts,
the light absorbed by chlorophyll supplies the energy ’used by plants to transform carbon dioxide
and water into oxygen and carbohydrates, which have a general formula of Cx(H20)y.
Eight
x Oa +
x CO2 +), H20
r
chlorophyll
In this endothennic transformation, the energy of the light absorbed by chlorophyll is converted
into chemical energy stored ir~ carbohydrates (sugars and starches). This chemical energy drives
the biochemical reactions that cause plants to grow, flower, and produce seed.
Chlorophyll is ~6t a very stable compound; bright sunlight causes it to decompose. To maintain
the amount of chlorophyll in their leaves, plants continuously synthesize it. The synthesis of
chlorophyll in plants requires sunlight and warm temperatures. Therefore, during summer
chlorophyll is continuously broken down and regenerated in the leaves of trees.
Another pigment found in the leaves of many plants is
carotene. Carotene absorbs blue-green and blue light. The
light reflected from carotene appears yellow. Carotene is also
a large molecule (C40H36) contained in the chloroplasts of
many plants. When carotene and chlorophyll occur in the
same leaf, together they remove red, blue-green, and blue
light from sunlight that falls on the leaf. The light reflected by
the leaf appears green. Carotene functions as an accessory
http://scifun.chem.wisc.eduichemweek/fallcolr/fallcolr.html
I 1/16/04
absorber. The energy, of the light absorbed by carotene is
transferred to chlorophyll, which uses the energy in
photosynthesis. Carotene is a much morn stable compound
than chlorophyll. Carotene persists in leaves even when
chlorophyll has disappeared. When chlorophyll disappears
from a leaf, the remaining carotene causes the leaf to appear
yellow.
A third pigment, or class of pigments, that occur in leaves are
the anthocyanins. Anthoeyanins absorb blue, blue-green, and
green light. Therefore, the light reflected by leaves containing
anthocyanins appears red. Unlike chlorophyll and carotene.
anthocyanins are not attached to cell membranes, but are
dissolved in the cell sap. The color produced by these
pigments is sensitive to the pH of the cell sap. lfthe sap is
quite acidic, the pigments impart a bright red color, if the sap
is less acidic, its color is more purple. Anthoeyanin pigments
are responsible for the red skin of ripe apples and the purple
of ripe grapes. Anthocyanins are formed by a reaction
between sugars and certain proteins in cell sap. This reaction
does not occur until the concentration of sugar in the sap is
quite high. The reaction also requires light. This is why
apples often appear red on one side and green on the other:
the red side was in the sun and the gt?een side was in shade.
Paper birch
During summer, the leaves of trees are factories
producing sugar from carbon~tioxide and water by
the action of light on chlorophyll. Chlorophyll causes
the leaves to appear green. (.The leaves of some trees.
such a~ birches and cottonwoods, also contain
carotene: these leaves appear brighter ~reen. because
carotene ~bsorbs blue-green light.) Wa~er and
nutrients flow from the roots, through the branches.
and into the leaves. The sugars produced by
photosynthesis flow from the leaves to other parts of
the tree. where some of the chemical energy is used
for growth and some is stored: The shortening days
and cool nights of autumn trigger changes in the tree.
One of these changes is the growth of a corky
Red Maple .
membrane between the branch and the leaf stem. This
membrane interferes with the" flow of nutriants into the leaf. Because the nutrient flow is
interrupted, the production of chlorophyll in the leaf declines, and the green color of the leaf fades.
If the leaf contaifis carotene, as do the leaves of birch and hickory, it will change from green to
bright yellow as the chlorophyll disappears. In some trees, as the concentration of sugar in the leaf’
increases, the sugar reacts to form anthoeyanins. These pigments cagse the yellowing leaves to
turn red. Red maples, red oaks, and sumac produce anthocyanins in abandanee and display the
brightest reds and purples in the autumn landscape.
The range and intensity of autumn colors is greatly
influenced by the weather. Low temperatures destroy
chlorophyll, and if they stay above freezing, promote
the formation of anthocyanins. Bright sunshine also
destroys ehlorophylI and enhances anthocyanin
production. Dry weather, by increasing sugar
concentration in sap, also increases ~e amount of
anthocyanin. So the brightest autumn colors are
produced when dry, sunny days are followed by cool,
dry niahts.
11116/04
THE CHEMISTRY OF AUTUMN COLORS
1. Name two environmental factors that stimulate trees to prepare for winter.
2. Explain why chlorophyll appears green.
3. What conditions cause chlorophyll to decompose? What type of temperatures promote the
synthesis of chlorophyll?
What is carotene AND what colors does it reflect? Are carotenes present all the time?
5. What function does carotene perform AND what happens to carotene when chlorophyll breaks do~?
6. What are anthocyanins AND what colors do they reflect?
7. Where are anthocyanins found in the cell AND what happens to them if the pH is raised (less acidic)?
8. Name two factors that affect the formation of amhoyanins.
9. What forms between the branch and the leaf stem (petiole)?
10. Describe three ways that this corky, membrane influences events in the leaf.
1 I. Explain how temperature, sunshine, and moisture levels SPECIFICALLY affect autumn leaf colors.
12. What conditions are best for the brightest autumn colors.
WHY STUDY PHOTOSYNTHESIS?
By Devens Gust, Ph:D:
Pro fessor of Chemistry,:,and Biochemistry
Center for the Study of Early Events in Photosynthesis
What is photosynthesis?
Photosynthesis is arguably the most important biological process on earth. By liberating oxygen and
consuming carbon dioxide, it has transformed the world into the hospitable environment we know today.
Directly or indirectly, photosynthesis fills all of our food requirements and many of our needs for fiber and
building materials. The energy stored in petroleum, natural gas and coal all came from the sun via
photosynthesis, as does the energy in firewood, which is a major fuel in many parts of the world, This being
the case, scientific research into photosynthesis is vitally important. If we can understand and control the
intricacies of the photosynthetic process, we can learn how to increase crop yields of food, fiber, wood,
and fuel, and how to better use our lands. The energy-harvesting secrets of plants can be adapted to
man-made systems which, provide new, efficient ways t’o collect and use solar energy. These same natural
’"technologies" can help point the way to the design of new, faster, and more compact computers~ and
even to new medicql breakthroughs. Because photosynthesis helps control the makeup of our
atmosphere, understanding photosynthesis is crucial to understanding how carbon dioxide and other
"greenhouse gases" affect the global climate. In this document, we Will briefly explore each of the areas
mentioned above, and illustrate how photosynthesis research is critical to maintaining and improving our
quality of life.
Photosynthesis and food. All of our biological energy needs are met by the plant kingdom, either directly or
through herbivorous animals. Plants in turn obtain the energy to synthesize foods’tufts via photosynthesis.
Although plants draw necessary materials fromthe soil and water and carbon dioxide from the air, the
energy needs of the plant are filled by sunlight. Sunlight is pure energy. However, sunlight itself is not a very
useful form of energy; it cannot be eaten, it cannot turn dynamos, and it cannot be stored. To be
beneficial, the energy in sunlight must be converted to other forms. This is what photosynthesis is all about.
If is the process by which plants change the energy in sunlight to kinds of energy that can be stored for
later use. Plants cam/out this process in photosynthetic reaction centers. These tiny units are found in
leaves, and convert light energy to chemical energy, which is the form used by all living organisms. One of
the major energy-harvesting processes in plants involves usiog the energy of sunlight to convert carbon
dioxide from the air into sugars, starches, and other high-energy carbohydrates. Oxygen is released in the
process. Later, when the plant needs food, it draws upon the energy stored in these carbohydrates. We do
the same. When we eat a plate of spaghetti, our bodies oxidize or "burn" the starch by allowing if to
combine with oxygen from the air. This produces carbon dioxide, which we exhale, and the energy we
need to survive. Thus, if there is no photosynthesis, there is no food. Indeed, one widely accepted theory
explaining the extinction of the dinosaurs suggests that a comet, meteor, or volcano ejected so much
material into the atmosphere that the amount of sunlight reaching the earth was severely reduced. This in .
turn caused the death of many plants and the creatures that depended upon them for energy.
Photosynthesis and energy. One of the Carbohydrates resul;ring from photosynthesis is cellulose, which
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~(~,~
dn
lant
p matenal
makes up the bulk of drywoo
a other
d
" .When webum wood, we cony
eft the ce IIulose
back to carbon dioxide and release the stored energy as heat. Burning fuel is basically the same oxidation
process that occurs in our bodies; it liberates the energy of "stored sunlight" in a useful form, and returns
carbon dioxide to the atmosphere. Energy from bumir~g "biomass" is important in many parts of the world.
in developing countries, firewood continues to be critical to survival EthanoF{grain alcohol) produced
from sugars and starches by fermentation is a major automobile fuel in Brazil, and is added to gasoline in
some parts of the United States to help reduce emissions of harmful pollutants. Ethanol is also readily
converted to ethylene, which serves as a feedstock fo a large part of the petrochemical industry. If is
possible fo convert cellulose to sugar, and then into ethanol; various microorganisms carry out this process.
It could be commercially important one day.
Our major sources of energy, of course, are coal, oil and natural gas. These materials are all derived from
ancient plants and animals, and the energy stored within them is chemical energy that originally came
from sunlight through photosynthesis. Thus, most of the energy we use today was originally solar energy!
Photosynthesis, fiber, and materials. Wood, of course, is not only burned, but is an important material for
building and many other purposes. Paper, for example, is nearly pure photosynthetically produced
cellulose, as is cotton and many other natural fibers. Even wool production depends on
photosynthetically-derived energy. In fact, all plant and animal products including many medicines and
drugs require energy to produce, and that energy comes ultimately from sunlight via photosynthesis. Many
of our other materials needs are filled by plastics and synthetic fibers which are produced from petroleum,
and 6re thus also photosynthetic in origin. Even much of our metal refining depends ultimately on coal or
other photosynthetic products. Indeed, it is difficult fo name an economically important mafedal or
substance whose existence and usefulness is not in some way tied to photosynthesis,
Photosynthesis and the environment. Currently, there is a lot of discussion concerning the possible effects of
carbon dioxide and other "greenhouse gases" on the environment. As mentioned above, photosynthesis
converts carbon dioxide from the air to carbohydrates and other kinds of "fixed" carbon and releases
oxygen to the atmosphere. When we.burn firewood, ethanol, or coal, oil and other fossil fuels, oxygen is
consumed, and carbon dioxide is released back to the atmosphere. Thus, carbon dioxide which was
removed from the atmosphere over millions of years is being replaced very quickly through our
consumption of these fuels. The increase in carbon dioxide and related gases is bound to affect our
atmosphere. Will this change be large or small, and will it be harmful or beneficial? These questions are
being actively studied by many scientists today. The answers will depend strongly on the effect of
photosynthesis carried out by land and sea organisms. As photosynthesis consumes carbon dioxide and
releases oxygen, it helps counteract the effect of combustion of fossil fuels. The burning of fossil fuels
releases not only carbon dioxide, but also hydrocarbons, nitrogen oxides, and other trace materials that
pollute the atmosphere and contribute to long-term health and environmental problems. These problems
are a consequence of the fact that nature has chosen to implement photosynthesis through conversion of
carbon dioxide to energy-rich materials such as carbohydrates. Can the principles of photosynthetic solar
energy harvesting be used in some way to produce non-polluting fuels or energy sources? The answer, as
we shall see, is yes.
Why study photosynthesis?
Because our quality of life, and indeed our very existence, depends on photosynthesis, it is essential that
we understand it. Through understanding, we can avoid adversely affecting the process and precipitating
environmental or ecological disasters. Through understanding, we can also learn to control photosynthesis,
and thus enhance production of food, fiber and energy. Understanding the natural process, which has
been developed by plants over several billion years, will also allow us to use the basi~; chemistry and
physics of photosynthesis for other purposes, such as solar energy conversion, the design of electronic
circuits, and the development of medicines and drugs. Some examples follow.
Photosynthesis and agriculture. Although photosynthesis has interested mankind for eons, rapid progress in
understanding the process has come in-the last few years. One of the things we have learned is that
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overall, photosynthesis is relatively inefficient. For example, based on the amount of carbon fixed by a field
of cam during a typical growing season, only about ] - 2% of the solar energy falling on the field is
recovered as new photosynthetic products. The efficiency of uncultivated plant life is only about 0.2%. In
sugar cane, which is one of the most efficient plants, about 8% of the light absorbed by the plant s
preserved as chemical energy. Many plants, especially those that originate in the temperate zones such
as most of the Unffed States, undergo a process called photorespirafion. This is a kind of "short circuit" of
photosynthesis that wastes much of the plants’ photosynthetic energy. The phenomenon of
phoforespirafion including its function, if any, is only one of many riddles facing the photosynthesis
researcher.
If we can fully understand processes like photorespiration, we will have the ability to alter them. Thus, more
efficient plants can be designed. Although new varieties of plants have been developed for centuries
through selective breeding, the techniques of modern molecular biology have speeded up the process
tremendously. Photosynthesis research can show us how to produce new crop strains that will make much
better use of the sunlight they absorb. Research along these lines is critical, as recent studies show that
agricultural production is leveling off at a time when demand for food and other agricultural products is
increasing rapidly.
Because plants depend upon photosynthesis for their survival, interfering with photosynthesis can kill the
plant. This is the basis of several important herbicides, which act by preventing certain important steps of
photosynthesis. Understanding the details of photosynthesis can lead to the design of new, extremely
selective herbicides and plant growth regulators that have the potential of being environmentally safe
(especially to animal life, which does not carry out photosynthesis). Indeed, it is possible to develop new
crop plants that are immune to specific herbicides, and to thus achieve weed control specific to one crop
species.
Photosynthesis and energy production. As described above, most of our current energy needs are met by
photosynthesis, ancient or modem, increasing the efficiency of natural photosynthesis can also increase
production of ethanol an’d of her fuels derived from agriculture. However, knowledge gained from
photosynthesis research can also be used to enhance energy production in a much more direct way.
Although the overall photosynthesis process is relatively wasteful, the early steps in the conversion of
sunlight to chemical energy are quite efficient. Why not learn to understand the basic chemistry and
physics of photosynthesis, and use these same principles to build man-made solar energy harvesting
devices? This has been a dream of chemists for years, but is now close to becoming a reality. In the
laboratory, scientists can now synthesize artificial photosynthetic reaction centers which rival the natural
ones in terms of the amount of sunlight stored as chemical or electrical energy. More research will lead to
the development of new, efficient solar energy harvesting technologies based on the natural process.
The role of photosynthesis in control of the environment. How does photosynthesis in temperate and
tropical forests and in the sea affect the quantity of greenhouse gases in the atmosphere? This is an
important and controversial issue today. As mentioned above, photosynthesis by plants removes carbon
dioxide from the atmosphere and replaces it with oxygen. Thus, if would tend to ameliorate the effects of
carbon dioxide relec~;ed by the burning of fossil fuels. However, the question is complicated by the fact
that plants themselves react fo the amount of carbon dioxide in the atmosphere. Some plants, appear to
grow more rapidly in an atmosphere rich in carbon dioxide, but this may not be true of all species.
Understanding the effect of greenhouse gases requires a much better knowledge of the interaction of the
plant kingdom with carbon dioxide than we have today. Burning plants and plant products such as
petroleum releases carbon dioxide and other byproducts such as hydrocarbons and nitrogen oxides.
However, the pollution caused by such materials is not a necessary product of solar energy utilization. The
artificial photosynthetic reaction centers discussed above produce energy without releasing any
byproducts other than heat. They hold the promise of producing clean energy in the form of electricity or
hydrogen fuel without pollution. Implementation of such solar energy harvesting devices would prevent
pollution at the source, which is certainly the most efficient approach to control.
Photosynthesis and electronics. At first glance, photosynthesis would seem to hage no association with th~
design of computers and other electronic devices. However, there is potentially a very strong connectic
A"goal of modem electronics research is to make transistors and other circuit campanent s as small as ..
possible. Small devices and short connections between them make computers faster and more compact.
The smallest possible unit at a material is a molecule (made up cxf Otoms of various types). Thus, the smallest
conceivable transistor is a single molecule (or atom). Many researchers today are investigating the
intriguing possibility of making electronic components from single molecules or small groups of molecules.
Another very active area at research is computers that use light, rather than electrons, as the medium for
carrying information. In principle, light-based computers have several advantages over traditional designs,
and indeed many of our telephone transmission and switching networks already operate through fiber
optics. What does this have to do with photosynthesis? It turns out that photosynthetic reaction centers are
natural photochemical switches of molecular dimensions. Learning how plants absorb light, control the
movement of the resulting energy to reaction centers, and convert the light energy to electrical, and
finally chemical energy can help us understand how to ma~e molecular-scale computers. In fact, several
molecular electronic logic elements based on artificial photosynthetic reaction centers have already
been reported in the scientific literature.
Phofosynthesis and medicine. Light has a very high energy content, and when it is absorbed by a
substance this energy is converted to other forms. When the energy ends up in the wrong place, it can
cause serious damage to living organisms. Aging of the skin and skin cancer are only two of many
deleterious effects of light on humans and animals. Because plants and other photosynthetic species have
been dealing with light for eons, they have had to develop photoprotective mechanisms to limit light
damage. Learning about the causes of light- induced tissue damage and the details of the natural
photo’protective mechanisms can help us can find ways to adapt these processes for the benefit of
humanity in areas far removed from photosynthesis itself. For example, the mechanism by which sunlight
absorbed by photosynthetic chlorophyll causes tissue damage in plants has been harnessed for medical
purposes. Substances related to chlorophyll localize naturally in cancerous tumor tissue, illumination of the
tumors with light then leads to photochemical damage which can kill the tumor while leaving surrounding
tissue unharmed. Another medical application involves using similar chlorophyll relatives to localize in
tumor tissue, and thus act as dyes which clearly delineate the boundary between cancerous and healthy
tissue. This diagnostic aid ~does not cause photochemical damage to normal tissue because the principles
of photosynthesis have been used to endow it with protective agents that harmlessly convert the
absorbed light to heat.
Conclusions
The above examples illustrate the importance of photosynthesis as a natural process and the impact that it
has on all of our lives. Research into the nature of photosynthesis is crucial because only by understanding
photosynthesis can we control it, and harness its principles for the betterment of mankind. Science has only
recently developed the basic tools and techniques needed to investigate the intricate details of
photosynthesis. It is now time to apply these tools and techniques to the problem, and to begin to reap the
benefits of this research.
--Written by and C0py~’ight (C) 1996 Devens Gust, Professor of Chemistry and Biochemistry, Arizona State
University
Professor Devens Gust’s Home Pa£e
Read another article by Dr. Gust, Research Trends: Emulating Photosynthesis
Visit the ASU Photosynthesis Center
revised Friday, Avgust 14, 1998
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[] Photosystem !i ,
[] Hydrogen
Ion Movement
Chloroplast
ATP synthase
Inner
Thylakoid
Space
4 + 02
Thylakoid
Membrane
2 NADP+
ADP
Stroma
f [] Electron
~ransport Chain
Photosystem I
ATP Formation
Summary of the Light dependent reaction in photosynthesis
1. Pigments in photosystem II absorb light.
2. Energy from that light is absorbed by electrons increasing their energy level.
3. So now these electrons are high energy and can be (they are) passed onto the electron
transport chain.
4. There are enzymes on the irmer surface of the thylakoid that break up two water
molecules into 2 H+ ions, 1 oxygen atom and 2 electrons
H O H+H +O
5. The oxygen is released as a gas and the H+ ions are released inside the thylakoid
memebrane.
6. So now high energy electrons move from Photosystem II to Phootsystem I. The
energy is used by the molecules in the electron transport chain to transport H+ ions from
the stroma into the inner thylakoid.
7. Pigments in Photosystem I use light energy to reenergize the electron.
NADP+ picks up these eiectrons plus a H+ ion ---) NADPH
8. Now the inside of the thylakoid membrane is positively charged. (Which is a result oft
H+ ion released during water splitting and electron transport. The outside becomes
negatively charged.
This difference in charges across the membrane provides the energy to make ATP.
9. ATP synthase is a protein in the membrane that allows H+ ions to pass through.
Class
Flowchart
The tCollowing.flowchart represents th~ reactions qf photosynthesis. Fill in the
mis~ing information u~ing the formulas listed below.
NADP÷
H20
ATP
C02
ADP + P
NADPH
Light
LightDependent
Reactions
Calvin
Cycle
Teaching Resources / Chapter
Biology Intemet Assigrunent on Photosynthesis-
Log on to the intemet
go to google.com type in biology I Interactive animations
Go to the section on Photosynthesis and Plants
Choose the last entry which is Photosynthesis Forest Biology Virginia Tech
First a leaf will appear and then you will see a close up of a leaf, label the diagram
in this packet from the diagram
push the CONTINUE BUTTON
Draw a picture of the cell labeling the cell wall, vacuole, nucleus, chloroplasts and
cytoplasm
push the CONTINUE BUTTON
Draw a picture of the enlarged chloroplast labeling: the outer and inner
membranes, thylakoids, stroma
push the CONTINUE BUTTON
You will see 5 points of interest on the inner membrane space.
Push number 1 - which is at PS 11 (photosystem II) Listen and watch the clip and
fill in the blanks below.
When light hits the P680 molecule of PS II, electrons are
and become
New electrons are reduced by splitting water which produces
and
~ Go back to the main menu and choose the second point ofinterest~
Point #2 - When electrons are passed from PSI1 to PS~ what happens to the hydrogen
ions?
Go back to the main menu and choose the third point of interest.
Point #3 - More light strikes the PS 700 molecule of PSI and eiectrons are
and become
Go back to the main menu and choose the fourth point of interest.
Point #4 - Electrons pass to an electron acceptor to NADP+ which is
becomes NADPH which is
and
Go back to the main menu and choose the fifth point of interest.
Pointe #5 - When the H+ ions concentrated on the inside diffuse through ATPase what is.
produced.
Where did the H+ ions come from (look back at your answers)
What are the final products that go onto the dark reaction of photosynthesis? there are 2.
Chloroplast
Pigment Analysis
EXPLORATION
~When you look at a leaf, the green pigment chlorophyll is usually
the only pigment that appears to be present. Actually, chlorophyll
is only one of many types of pigments present in the leaf and one of
several that are involved in the process of photosynthesis. Once
removed from the leaf, the photosynthetic pigments can be
separated from one another and identified using a process called
chromatography.
Chromatography is a physical process in which several
compounds are separated from a solution and from each other. In
thin layer chromatography, the solvent is absorbed by a thin layer
of silica gel. As the solvent moves upward in the gel, it carries with
it the compounds that have been placed on the gel. These
compounds each move upward at a specific rate in relation to the
moving solvent and can be identified by the dlstances they move.
OBJECTIVES
¯ Extract a mixture of plant photosynthetic
pigments. "
¯ Separate pigments of spinach leaves by thin layer
chromatography.
baby food jar with lid
spinach leaves, dried
chromatography solvent
thin layer chromatography slide
funnel
cheesecloth
dark-colored bottle or vial
goggles
PROCEDURE
Part A. Preparing For Chromatography
2o
¯ Prepare and analyze a silica gel chromatogram.
¯ Calculate the R~ values for various photosynthetic
pigments.
Obtain a small amount (approximately 5 mL) of
the chromatography solvent from your teacher.
Pour enough of this solvent into the baby-food
iar so that it just covers the bottom of the jar,
but is less than 1 mm deep. Screw the cap onto
the jar and set aside for later use.
Place a pea-sized amount of dried spinach in a
mortar. Using the pestle, grind up the spinach
for 2 minutes. Add 2 mL ot ethyl alcohol to the
ground spinach and continue to grind for
another 2 minutes as shown in Figure 1. The
product should be a deep green fluid. Filter this
fluid through a double layer of cheesecloth into
a dark-colored bottle or vial. Stopper the bottle
tightly until needed.
capillary tube
metric ruler
pencil
ethyl alcohol
mortar and pestle
laboratory apron
Part B. Making and Analyzing th~
Chromatogram
I. Select a chromatog~’aphy slide¯ Handle it only
by its edges. Make a small pencil dot 5 mm
from the bottom of the slide. DO NOT use a pen
to make the dot.
2. Dip a capillary tube into the pigment-containing
fluid in the dark bottle.
3, Lightly touch the filled end of the capillai~ tube
to the dot on the .coated slide as shown in
Figure 2. Allow a small amount of the fluid to be
deposited on the slide, forming a spot I mm in
diameter. Do not disturb the silica film above
the spot. Allow the spot to dry l~about 30
seconds).
4. Repeat step 3, applying leaf pigments to the
same spot four or five times, being sure to
allow the spot to dry each time. This will
produce a concentrated spot of pigments.
5, Hold the slide along the outside of the jar to
verify that the spot will not be below the level
of the solvent. If the solvent is too deep pour a
little of it out of the jar into a specially labeled
container. Place the slide into the baby food iar
on a level surface as shown in Figure 3. Do not
allow the spot to contact the solvent at any
time. Quickly screw the cap on the jar. Do not
move the jar once the slide is placed in the
solvent.
6. Watch the slide closely and note the movement
of solvent up the film of silica gel. Remove the
slide from the baby food jar when the solvent
front nearly reaches the top of the slide.
7. Mark the top of the solvent front with a pencil
as shown in Figure 4.
8. Make a drawing of your slide in the space
provided in Data and Observations. Be sure to
indicate the position of the original spot of
pigments as well as the locations of pigments
anywhere else on the slide. Indicate the relative
amounts of pigments in each spot by drawing
the spots the same size and darkness as those
on your slide.
Carotenes, which are yellow or orange pigmentsl
usually appear near the top of the slide. Lutein is a
gray pigment iust below the carotenes. Chlorophyll
a will appear next as a blue-green pigment.
Xanthbphylls are yellow pigments, and chlorophyll b
is a yellow-green pigment. They are found together
lust below chlorophyll a. Your chromatogram may
or may not have all of these pigments.
9. Measure with a metric ruler the distance in mm
from the original spot to the solvent front you
marked in step 7. Record this measurement in
Table I.
4O
Figure 4.
I
compounds, an unknown substance ca~ be
10. Measure the dist~ce each pigr~ent traveled
from the original spot to its final location.
identified.
Record these data in Table 1.
distance pigment traveled
11. Calculate the R~ value for each pigment spot.
distance solvent traveled
The Ph value is the ratio of the distance traveled
by the pigmen~ to the distance traveled by the 12. Record your R, values in Table l.
solvent. By comparing Ph values of unknown
13. Clean your equipment and dispose of your
solvents in the designated container.
compounds with the P~ v~ues of known
DATA AND OBSERVATIONS
Table 1.
Chromatography Data
Substance
Distance from
original spot (mm)
Solvent front
Carotends
Lutein
Chlorophyll a
Xanthophylis
Chlorophyll b
Your thin layer slide
ANALYSIS
1. Which pigments were you able to identify?
2. Judging from the darkness of the pigment spots on your chromatogram, which pigment would you say is
most abundant in spinach leaves?
3. Which pigment appeared to travel the fastest?
slowest?
4. Which pigment had the highest R, value?
5. How do R~ values compare with the rate of trave’, o! the pigment?
6. Why do the pigments travel in the solvent at different speeds? Remember that each pigment is a different
molecule with its own characteristic size and mass.
41
~ "L Do you think you would get simila~ result~ if.you used a diflerent k~nd of leaf?. Explaln.
8. Why do leaves appear green even though there are other pigments present? ,
9. Many leaves change color in the autumn. How is It possible for this color change to occur? Base your
answer on your new knowledge of pigments present In leaves. (HINT: Chlorophyll a and chlorophyll b
are broken down in autumn when day length begins to shorten and temperatures decrease.)
FURTHER EXPLORATIONS
1. Conduct this Exploration using several different plants with
differently colored leaves to see how their leaf pigments compare
with’those of spinach.
2. Separate pigments in spinach leaves by paper chromatography and
compare the results with those obtained by thin layer "
chromatography.
42
Photosystem Model = hands on activity see page T165- Biology Exploring Life
Objective-To model the result of light striking a photosystem
Time 20 min
Skills Focus using models
Materials (per group of 6)
Markers
paper(index cards)
string for signs
a flashligh
4 tennis balls to represent electrons
Procedure
1. Have students write "e-" on each of the tennis balls, then create signs with the
following labels:
chlorophyli 1
chlorophyll 2
chlorophyll 3(reaction-center chlorophyll)
Primary electron carrier
water molecule
light source
punch holes in cards and attach string so students can wear around their neck,
2. To act out the process, have students choose roles axad put the signs on. The three
chlorophyll molecules sit down, each holding a tennis-ball electron. The Primary
Electron Carrier and the Water Molecule stand near Chlorophyll 3 the water molecule
hiding a tennis-ball electron behind its back.
3. The light Source shines the flashlight on the chlorophyll molecules. As the light shines
on chlorophylll, chlorophyll 1 gets up "excited"-standing up quickly and waving its
electron then "wakes up " chlorophyll 2. Chlorophyll 2 stands up excitedly and wakes
up Chlorophyll 3 while Chlorophyll 1 sinks back down, "exhausted". Chlorophyll 2 sits
down next. Then Chlorophyll 3 gets up and waves its electron, the Primary Electron
Acceptor grabs it. Chlorophyll 3 then sits back down acting startled to have "lost " its
electron. The Water Molecule comes over, waves it electron, and hands it to chlorophyll
3.
Follow-up
Have students draw diagrams representing the process they just modeled and add
captions to explain each step
Investigation
26
Leaf Stomata
Learning Objectives
To determine the locations and
density of stomata on a leaf.
To describe the effect of an environmental change on stomata.
Where are stomata located on a leaf,
and how do they work?
Process Objectives
To observe the effect of sail on
stomata and guard cells.
To hypothesize about the response of guard cells to a
stimulus.
¯ - To predict how a change in stomata influences photosynthesis.
If asked which plant organ is essential in absorbing compounds for a plant,
most people would say it is the root. But roots are not the only plant organs
involved in absorbing important compounds_. "Leaves absorb and release
gases, such as oxygen, carbon dioxide, and water vapor. As you might guess,
gas exchange in a leaf affects the process of photosynthesis.
Materials
For Group of 4
Distilled water in a small beaker
with a dropper
5% NaCI solution in a small
beaker with a dropper
For Each Student
¯ 1-3 Microscope slide(s)
¯ Leaves from a watered, nonwilted
plant exposed to light
Razor blade or pair of forceps
1-3 Coverslip(s)
¯ Compound microscope
¯ Paper towel
Introduction
Prelab Preparation
Think about the functions of gas exchange between a leaf and the atmosphere.
Consider the roles of oxygen, carbon dioxide, and water in photosymhesis
and in aerobic respiration within the cells of the leaf.
1. During what part of the 24-hour day would maxim~Jm exchange of gases be most likely to occur? Why?
2. Under what environmental conditions would a plant benefit
from reducing loss of water vapor through the leaves? Why?
3. What mechanism would you design to allow gas exchange
between a leaf and the atmosphere?
4. How could your mechanism control the flow of gases into and
out of the leaf, opening to increase the rate of gas exchange,
and closing to reduce water loss?
Structures, perhaps similar to the one you would design, are present in the
epidermis (outer cell layer) of the leaves of many plants. These structures
consist of openings called stomata (singular, stoma), that allow water.vapor
and gases to enter and exit the leaf. Two guard cells surrounding each stoma
regulate its opening and closing. Review the functioning of stomata and
guard cells in Section 26.4 of your textbook. In this investigation, you will
examine the epidermis of a leaf under a microscope to observe leaf stomata.
Procedure
A. Place a drop of water on a microscope slide. Obtain a healthy, nonwihed
leaf from one of the available plants. Holding the bottom surface of the
leaf toward you, fold the leaf in half toward you so that the bottom surfaces are together. (See the illustration on page 158.) Unfold the leaf and
tear it along the crease by holding the left section of the leaf and pulling
the right section down at an angle. A clear, colorless outer layer should
be visible along the tprn edge. This layer is the lower epidermis.
B. Carefully cut off a small fragment of the transparent epidermal layer with
a razor blade or pull it off carefully with forceps. Immediately place the
fragment in the drop of water on your microscope slide and position a
coverslip over it. Do not allow the fragment to dry out.
Investigation 26
157
C. F_,xandne the ~pidvrmis through the low-power objective of your micro.
scope. Observ~ the sizes and shapes of the living ceils in the epidermis.
The small bean-shaped cells occurring in pairs arc guaxd cells.
5. Make an outline drawing of a pair of guard cells and the surStrategy for Observing
rounding epidermal ceils.
Draw the guard c~lls as soon as you
make yo~g obs~wadons of the epi- D. Examin~hhepairofguardcellsund~rthchlgh.pow~robjecfive. The
dermis.
opening or pore visible between the guard cells is the stoma.
6. How does the wall of a guard cell vary in thickness? Add this
detail to Your drawing.
£. Return the microscope objective to low power.
7. HOW many stornata are visible in one low power field?
8. Compare your data with those of other students. What conclusions can you draw about the density of stomata?
F. Repeat Steps A through E with another ]eaf from the plant you have been
using, but this time examine the upper epidermis. Holding the top surface of the leaf toward you, fold the leaf in half toward you so that the top
surfaces are together. Theu, tear the leaf along the crease, as you did in
Step A, to obtain a fragment of the upper epidermis.
9. How many stomata are visible in your 1ragment of upper epi3
dermis under low power?
10. What conclusion can you draw about the ~ocati0ns and densities of stomata on leaves from your species of plant? What
advantage wou~d this have for the p~ant?
11. Where would you expect to find stomata on a water lily leaf?
Why would you expect to find them there?
Guard
cells conu’ol the movement of water raper and gases beween the
G,
leaf and the aUnospbere by opening and closing the stomata.
12. State a hypothesis describing guard cell response to water
loss and the effect of this response on a stoma.
Make a flesh wet mount of the lower epidermis of a leaf. Observe a
Strategy for Hypothesizing
stoma under high power. Place a drop of 5% NaCI solution at the edge of
Your h~pothesis should be testable.
the coverslip. Take a piece of paper towel and touch it to the opposite
As you generate hypotheses, think of
edge of the coverslip. The paper towel should draw out the water that
experiments you could design to test
bathes the epidermis, and the NaCt solution should replace the water.
This will create a concenla’ation gradient between the cells and their environment. Water will move out of the guard cells by osmosis until the salt
concentration inside the cells is the same as it is outside. Allow 5 minutes for osmosis to be completed, then observe the guard cells and stoma
again.
13. What has happened to the guard cells and to the s~oma?
14. What property of guard cells permits such a change?
15. Do your experimental results support your hypothesis?
Postlab Analysis
Strategy for Predicting
List several predictions. Select the
prediction most likely to be accurate
based on your hypothesis (see Question 12).
158
lnvesdgation 26
16. In what way would the normal pattern of gas exchange between a leaf and the atmosphere be altered by coating both
sides of the leaf with petroleum jetty or wax?
17. Predict what would happen to guard ceils and stomata on a
hot, dry day. How might this affect photosynthesis? Why?
Further Investigation
1. Compare stomata on leaves from well-watered plants kept in dark with
stomata on leaves from well-watered plants kept in light.
¯ Prepare a wet mount of the onion epidermis
using a law drops of water.
¯ View the wet motmt under low, then high power
magnification.
If the epidermis is not clearly visible, there is
probably still part of the soft celluL~ materi~ o~
the leaf present. If so, repe~t the scraping of the leaf
with a new g~een onion section. It may ta~ke several
tries to obtain only the epidermis.
¯ Under high power magnification, identify structures using Figure 52-3 and the following descrip-
In) epidermis cells--long, diamond-shaped
cells
[b) guard cells--half circle-shaped cells
leaf epidermis
(cJ stomata--small spaces or openings between
two guard cells
¯ Use the space provided to diagram what you see
{dJ clzloroplasts--green dotlike parts within the
under high power. Label guard cell, stomata,
guard cells"
chloroplasts, epidermal cell.
Analysis
1. What is the major function of leaves?
2. [a] What pigment is present m certain leaf tissues that allows a lea~ to carry on its major ~unction?
(b) What color is this pigment? _~_
3. List all tissues or cells obscrved or described in this investigation that allow a leaf to carry on its major
fu ,notion.
What is the Ktnction of each of the following tissues or structures? [See Part A.)
(a} epidermis"
(c] guard ceils
(d~ stomate_
ie) palisade lnyer _
"
FiGUR~ 52-1
Observing Stomata
¯ place a .~~ion ~f g~een onion lsaf on a
microscope slide,
¯ Scraping in one d~reetion only, use a single edge
razor blade to gently scrape away the soft cellular
m~tenal ~rom the in~de of the leaf. Use Figure
51-2 as a ~aide.
¯ Continue scraping the le~E until o~ly the outer,
transparent epidermis remams,
¯ With a razor blade, slice the lea~ section so it lies
flat on the slide as shown in Fi~zre 52-2.
CAUTION: Blade is shaw. Cu: away from
lingers, Make sure the ori~ns!, outside smface of
the lea~ xs d~wn.
FIGURE 52-2
onion leaf
~ 1-6-./---- s’~
Page 6 of 8
fhe in and out of stomata
Suggested Photoperiod Procedure:
Three sample slides were made every hour, over a 24-hour period, using the same tree. Each sample
was taken from three different areas of the tree. Humidity, light intensity, and temperature were
recorded with each sample.
To analyze the data, images were captured using a flex-cam attached to a compound microscope (400x).
A "Snappy-cam" (video capturing device) was used to photograph the imprints on the slide. These
images were then transferred to "_S_C_ IONI.M_A_ GE" for total area measurement of stomatal pore openings
(at 400x, the entire stomata has a length of 20microns). Scionlmage can be downloaded free from the
intemet!
This procedure can be altered to fit any student-generated hypotheses mentioned in the summary section
above.
If you do not have access to a flex-cam, snappy-cam and scionlmage, an alternative way to assess the
area of the open pores is to compare them to the following images, photographed using a compound
microscope (400x).
100%
open
75%
50%
15%
0-5%
open
25%
open
open
For sample results of this photoperiod lab~ click here - RESULTS.
Return to the
EVALUATION / ASSESSMENT:
Students demonstrate mastery of science concepts by completing the imprinting, data collection,
ht~p ://www.woodrow.org/teachers/bi/1998/stomataJ
12/19/2005
Leaf Stomata ( 75. points)
Scientific approach (13 points)
Prelab questions: 1-4 - Answer in complete sentences(8 points)
I. During what part of the 24 -hour day would maximum exchange of
gases be most likely to occur? Why?
Procedure: Write out what you did? (5 points)
Materials: List materials used(5 points)
Questions page 158 5-17 (26 points)
Relabel figure 52-1 (4 points)
Diagram of leaf epidermis
(5 points)
Analysis
#I 1 ptso
#2 a and b 1 point each
#3 ! points
#4 a-f (6 points)
SAFARI Montage: Quiz
Page 1 ofl
SAFARI
Quiz Questions For Photosynthesis
Use your browser’s Print page function to print this quiz.
1, Chloroplasts are found in the
A,
6.
C.
D.
of a leaf.
epidermis
chlorophyll
palisade layer
guard cells
2. What role does chlorophyll play in photosynthesis?
A.
B.
C.
D.
It produces starch from sugar molecules.
It releases energy that plants use for growth.
It absorbs light and transforms it into chemical energy.
It controls the amount of oxygen that is released by the plant into the
atmosphere.
3. During the Calvin Cycle, carbon is linked with hydrogen and oxygen to
make:
A.
B.
C.
D.
pigment.
sugars.
ATP.
starch.
4. Respiration is:
A. the opposite of photosynthesis.
B. the process a plant goes through to release water vapor through the
stomata.
C. the evolution of plants over 3.5 billion years.
D. how plants produce their own food out of carbon dioxide and water.
5. According to this show, how could artificial photosynthesis help in
future space flights?
A. Plants would be able to grow on Mars.
B. Plants would keep the air breaLhable on-board space ships.
C. Plants would produce enough food for space crews to survive over a long
period of time.
D. All of the above,
Back to Search Results
View Answers to Quiz
http ://sa~ari/S AFA£J/montage/displayquiz.php?S earchPage=tme&keyindex= 1014&locati... 10/23/2009
NAME
Photosynthesis
4.2
Section Review
The Big Idea!
All organisms get energy by breaking down the chemical compounds in food and making ATP
and other molecules, 4,
Concepts
¯ During photosynthesis, sunlight is converted into chemical energy, which is stored in
food.
¯ Photosynthetic pigments such as chlorophyll are contained in chloroplasts.
¯ The first stage of photosynthesis consists of light-dependent reactions in which light
energy is used to split water into oxygen, hydrogen ions, and electrons.
¯ In the second stage of photosynthesis, called the Calvin cycle, carbon d~oxide is converted
into glucose.
Words
photosynthesis
pigment
chlorophyll
chloroplast
Calvin cycle
PART A Match each term in the Data Bank with its description below. Write the letter of the correct
term on the line provided.
Data Bank
a. grana
e. photosynthesis
b. chlorophyll
c. stroma
f. pigment
g. photosystems
d. chloroplasts
1. process by which autotrophs convert sunlight to a usable form of energy
2. molecule that absorbs certain wavelengths of light and reflects or transmits others
3. most common and most important photosynthetic pigment in plants and algae
4. organelles that contain chlorophyll
$. gel-like matetial that surrounds the thylakoids ’
a. stacks of disk-shaped si:cUcrures that contain chlorophyll
7, light-coLlecting units of the chloroplast
PART B
1. What wavelengths of light are absorbed by chlorophyll? What wavelengths are reflected?
2, Why is light energy Important to the photosynthetic process?
Copyright © Addison Wesley Longman, Inc. All rights reserved.
Unit 1 Review Module
NAME
CLASS ,
In which stage of the photosynthetic process is oxygen produced? What happens to
this oxygen?
4. What chemicals are necessary for the Calvin cycle to occur? Where do these chemicals
come from?
$. What compound is formed from carbon dioxide in the Calvin cycle?
6. How do plants store energy they do not need immediately?
PART C Complete the following sentences by choosing the correct term from the Data Bank and
writing it on the line provided. Some terms may be used more than once.
Data ~ank
glucose
carbon dioxide
hydrogen ions
concentration gradient
starches
water
ATP
Calvin cycle
stroma
ADP
r,
electrons
1. Plants use energy from sunlight to split molecules of
, releasing
oxygen,
, and
in the light dependent reactions
of photosynthesis.
Using the energy of electrons produced in Photosystem II,
transported ~rom the stroma to the thylakoid space.
are actively
3. This movement of hydrogen ions into the thylakoid space creates a(n)
which provides energy for the conversion of
__ into
4. The process in which carbohydrates are formed from carbondioxide is called the
, which takes place in the
$. For every six molecules of
is produced.
that enter the Calvin cycle, one molecule of
Both autotrophs and heterotrophs convert the
photosynthesis into
of the chloroplast.
produced by
to power life functions.
Most piants store energy in the form of
, which are long strings of
molecules.
Unit 1 Review Module
Copyright © Addison Wesley Longman, inc. All right~ reserved.
NAM£ __
CLASS
DATE
Photosynthesis
PART A Answer the Following questions on the lines laro~ded.
1. W’nat is photos.~mthesis?
¯ 2. Vv2aa~ molecules, pzoduced b.v photosy~I.hesis, are used to store energy from the stm?
PART 8 Use ".he diagram of photosymthesis below to answer the following;
A ~
Ug~t
Light-Dependent
Reactions
~l C and D
E _I
Carbon fixation
(Calvin cycle)
¯F
I. Iden~i~ ~e compound each letter represents.
b.
d.
f.
How do plants obtain the carbon cLiox~de they need for photos.~rt~thesis?
DATE
CLASS
NAME
Work~heet 10
Hg~t-D, ependent
Light-Dependent Reactions
Uses light ene.z~" to split
¢. electron ca2Tier protein
Uses light ener~" to re-energi_ze
elec-~ons.
d. ATP sy~thase
Transfers elecl:rons between Lightcollecting molecules.
e. thylakoid space (2umen)
"
P|av
$. __i__ Re,on where hydrogen ions
accumulate when water is split
PART B Answer the following questions on the lines provided.
1. Explain the role o~f hght ener~" m t_he hght-dep, endent rea~-Xions.
,
P.~-~.,~..~- ~ -~ _,~ ~_ ~ ....
:2. Describe the location of photosystems I and II inside the chloroplast.
B. lVhat two high-ener~~ compounds are created by the light-dependent reaCtions?
Copyright © Acid son Vves ey Longrnan, Inc. All rlgnts reserved,
Anirnared .Biological Concepzs I $
Online Activity 8.2( closer look) and Activity 8.3
1 .Water (H20) is split in photosystem II to form two protons(H+), two electrons(E-) and
oxygen (O). What role do each of these products play in photosynthesis?
2. How man 3 - PGA molecules are produced from each reaction RuBP and CO2?
3. What type of molecule is mbisco?
4. Name the high-energy molecule that is required for the regeneration of RuBP/
5. What is the primary function of the Calvin cycle?
6. A plant used 18 ATP molecules in the formation of two G3P molecules that combine
to form glucose. When you eat a marshmallow containing sugar, how many ATP
molecules ~vill you make from one molecule of glucose?