Name: ___________________________________ Date:__________________________________ Pd:__________
Photosynthesis, Energy, Reading Homework
Annotate (20 pts) and read the following information. Complete the chart in Table A (20 pts) and the
diagram (10 pts).
Introduction
Through this series of activities you will explore the relationship and mechanisms of how the structure and
function of the chloroplast found in plants uses energy from the sun (light energy) and converts that energy
into chemical energy through the process of photosynthesis. The process of photosynthesis is represented by
the chemical equation:
6CO2 + 6H2O ------> C6H12O6 + 6O2
Sunlight energy
This equation is a simple representation of the complex process by which carbon dioxide and water are used
to form the nutrients necessary for maintaining life to nearly all living things on earth. The energy from the
sun is utilized by producers or autotrophs to form glucose which is the foundation for the energy pyramid
thereby driving the food web. Photosynthesis also plays an important role in the cycling of water, oxygen and
carbon.
Activity 1: Compare and Contrast PS2, PS1, and the Calvin Cycle
The process of photosynthesis converts light energy into energy storage molecules of ATP and NADPH by
splitting water. This energy is then used to fix carbon obtained from atmospheric CO2, to form glucose. This
is a two-step process. The first process is known as the light reaction. The light reaction produces energy
storing molecules through two pathways. Photosystem 2 and Photosystem 1. The systems were named in the
order that they were discovered, not in the order that they occur. Photosystem 2 is the first part of the light
reaction. The second process of photosynthesis is known as the Calvin Cycle or the dark reaction due to the
fact that it proceeds without receiving energy directly from light.
Photosystem 2 begins when particular wavelengths of light energy are collected in the thylakoid membrane of
the chloroplast by compounds called receptor molecules. These light harvesting molecules of chlorophyll pass
electrons through a series of enzymes; the energy becomes concentrated in an area known as the reaction
center. As the electrons flow through the Electron Transport Chain (ETC) they lose energy. The remaining
energy is concentrated in the reaction center and is used to split water. As a result of the decomposition of
water, elemental oxygen is formed and released into the atmosphere; the H+ ions remain in the thylakoid
membrane and electrons replace those that are lost to other electron acceptors. This process produces ATP.
Photosystem 1 also has a pigment complex that absorbs solar energy. The electrons that leave the reaction
center are captured by a different electron receptor molecule. The electrons move through an Electron
Transport Chain (ETC). When these electrons leave the reaction center they are captured by different electron
acceptors and produce ATP in addition to NADPH.
Essential Questions
1. What is the relationship between energy and wavelength that results the phenomenon of fluorescence?
2. Which wavelength(s) of light energy is absorbed by chlorophyll initiating the process of photosynthesis?
Name: ___________________________________ Date:__________________________________ Pd:__________
The Calvin Cycle or Dark Reaction occurs in the stroma of
the chloroplast. This step uses both ATP and NADPH
produced in Photosystem 2 and Photosystem 1 to produce
glucose by fixing carbon from carbon dioxide found in the
atmosphere. The products of photosynthesis, oxygen and
glucose, are the ultimate resources needed for life on
earth. Both autotrophs and heterotrophs contribute to
the carbon cycle; autotrophs, when they take CO2 from
the atmosphere and again, along with heterotrophs,
during cellular respiration.
1. COMPARE AND CONTRAST PS2, PS1 AND THE CALVIN CYCLE
Put an X in all of the boxes that make the following statements true
PS2
PS1
Calvin Cycle
2. Identify the flow of O2, CO2,
glucose, water, and energy
from sunlight in plants during
photosynthesis.
1st step in photosynthesis
also called the light reaction
also called the dark reaction
occurs in the chloroplast
reaction takes place in the
thylakoid membrane
water splits to form ATP
produces NADPH
reaction takes place in the
stroma
carbon dioxide is absorbed from
the atmosphere
involves electron transport
chain
Essential Questions
1. What is the relationship between energy and wavelength that results the phenomenon of fluorescence?
2. Which wavelength(s) of light energy is absorbed by chlorophyll initiating the process of photosynthesis?
Name: ___________________________________ Date:__________________________________ Pd:__________
Chlorophyll Lab
Fluorescence of Chlorophyll
PRELAB
Shine a fluorescent light on a spinach leaf and record your observations on the student data sheet.
BACKGROUND
When photosynthetic pigments absorb incoming light of various wavelengths the absorbed energy does not
disappear. When a pigment molecule absorbs a photon, one of the molecule’s electrons is elevated to an
orbital or energy level that gives it more potential energy (an orbital further away from the nucleus). When
the electron is in its normal energy level the pigment molecule is said to be in its ground state. After the
absorption of a photon, an electron is elevated to a higher energy level and the pigment molecule is said to be
in an excited state. The only photons absorbed are those whose energy is exactly equal to the energy
difference between the ground state and an excited state, and this energy difference varies from one kind of
atom or molecule to another. Subsequently, a particular compound absorbs only photons corresponding to
specific wavelengths, which is why each pigment has a unique absorption spectrum.
An electron in an excited state, as in all high-energy states, is unstable. Usually, the excited electrons of
accessory pigments drop back down to the ground state orbital in a billionth of a second, releasing their
excess energy as heat and photons. The afterglow (or photon release) is called fluorescence. The
fluorescence has a longer wavelength, and hence less energy than the light that excited the pigment.
Because the excited electrons of chlorophyll a are captured by primary electron acceptors located on the
membrane of the chloroplasts, fluorescence is not normally observed. The energy from these excited
electrons is converted to chemical energy as it passes through the electron transport chain (ETC) (via electron
acceptor molecules); the energy is used to break water molecules which releases O2 and H+ ions eventually
resulting in the formation of NADPH and ATP, which the cell uses to carry out its metabolic processes.
However, if the chloroplast’s thylakoid membrane is disrupted the excited electrons of chlorophyll a drop back
to ground state emitting photons and heat and fluorescence can then be observed.
SAFETY
Use goggles while grinding the leaves to extract the chlorophyll.
Avoid unventilated areas and open flames when using acetone.
MATERIALS
acetone (or isopropyl alcohol)
filter paper
flashlight or UV light
funnel
green leaves (spinach works well)
mortar & pestle
graduated cylinder
test tube & test tube rack
PROCEDURE
1. Remove any roots and stems from your plant; grind the green leaves using a mortar and pestle.
Essential Questions
1. What is the relationship between energy and wavelength that results the phenomenon of fluorescence?
2. Which wavelength(s) of light energy is absorbed by chlorophyll initiating the process of photosynthesis?
Name: ___________________________________ Date:__________________________________ Pd:__________
2. Add acetone (or isopropyl alcohol) to the ground leaves; use enough acetone and green leaves to get
about 10 – 15 ml of chlorophyll extract.
3. Fold a piece of filter paper in half and then in half again; open the paper funnel you have just made and
place it inside the funnel provided with your materials.
4. Filter the extract through the funnel into a test tube. Avoid tearing the filter paper.
5. Allow the extract to drip slowly through the filter paper until approximately 10 ml of the green
chlorophyll, extract solution accumulates in the bottom of the test tube.
6. In a very dark area of the room, shine the flashlight at a 90° angle onto the test tube containing the
chlorophyll extract solution.
7. Observe the fluorescence of the chlorophyll and answer question 2 under Prelab/Observations on your
student data sheet.
8. Answer analysis questions on Student Data Sheet
9. Perform Card sort activity and record arrangement on student data sheet.
ACTIVITY 2: FLUORESCENCE OF CHLOROPHYLL
PRELAB/OBSERVATIONAL DATA
1. What did you observe when the light was shined on the original spinach leaf?
2. What color does the chlorophyll fluoresce?
ANALYSIS
1. What normally happens when electrons in chlorophyll are excited by the sunlight and are collected by the
receptor molecules?
2. Discuss the effect that the destruction of the thylakoid membrane, which occurs when the green leaf is
ground up, has on the normal energy transfer between the accessory pigments and chlorophyll a. Be sure to
contrast what normally happens between the pigments and the effect of the thylakoid destruction.
3. Would you predict that the red fluorescence has more or less energy than the energy that was absorbed?
Explain your reasoning.
4. Using the card sort, arrange the colors in order from the highest energy level to the lowest energy level.
Record this arrangement
Essential Questions
1. What is the relationship between energy and wavelength that results the phenomenon of fluorescence?
2. Which wavelength(s) of light energy is absorbed by chlorophyll initiating the process of photosynthesis?
Name: ___________________________________ Date:__________________________________ Pd:__________
Activity 3: Absorbance of Chlorophyll
PRE-LAB
Answer the pre-lab questions on the Student Data Sheet.
INTRODUCTION
Light from the sun is used as fuel for photosynthesis. The light is absorbed by special molecules in plants
called pigments. Using a spectrophotometer, specific wavelengths (colors) of light will pass through a solution
containing pigments extracted from a plant.
SAFETY
1. Keep the pigment solution away from your mouth and eyes.
2. Do not consume any of the solution.
3. The solution will stain your clothing if spilled.
4. Keep the electrical cords away from water sources.
5. Do not spill any of the solution in the spectrophotometer.
MATERIALS
spectrophotometer
cuvettes
distilled water
pigment solution
spinach
funnels
test tubes w/stoppers
colored pencils
white paper strips
test tube holders
mortar and pestle
acetone
filter paper
black light
PROCEDURE
Using the Spectrophotometer to record color
1. Turn the power on.
2. Place a small piece of white paper in the cuvette holder.
3. Using the side arrows set the bottom indicator to %T (Transmittance).
4. Press the Calibration button on the bottom (CAL).
5. Adjust the wavelength to the values indicated on your data sheet using the top and bottom arrows.
6. Record on the data sheet each observation of color reflected onto the paper for each wavelength
indicated.
Using the Spectrophotometer to record absorbance
1. Pipette approximately 2 ml of chlorophyll solution (from the previous activity) into the cuvette.
2. Fill the rest of the cuvette with distilled water.
3. Using your pipette, gently mix the water and chlorophyll solution.
4. Place a cuvette of distilled water in the cuvette holder (clear sides towards the light source). Close the
lid.
5. With the setting still on %T, calibrate the distilled water to the wavelength indicated on the data table.
6. Remove the distilled water and place the cuvette with the chlorophyll solution in the cuvette holder
(clear sides towards the light source). Close the lid.
7. Using the side arrows change the bottom setting to absorbance.
8. Record the absorbance on the data table.
Essential Questions
1. What is the relationship between energy and wavelength that results the phenomenon of fluorescence?
2. Which wavelength(s) of light energy is absorbed by chlorophyll initiating the process of photosynthesis?
Name: ___________________________________ Date:__________________________________ Pd:__________
7. Repeat steps 7-11 for each wavelength given on the data table. You must calibrate using distilled
water every time the wavelength is changed.
8. Graph your results, color code the wavelengths.
ACTIVITY 2: FLUORESCENCE OF CHLOROPHYLL
PRELAB/OBSERVATIONAL DATA
1. What did you observe when the light was shined on the original spinach leaf?
2. What color does the chlorophyll fluoresce?
ANALYSIS
1. What normally happens when electrons in chlorophyll are excited by the sunlight and are collected by the
receptor molecules?
2. Discuss the effect that the destruction of the thylakoid membrane, which occurs when the green leaf is
ground up, has on the normal energy transfer between the accessory pigments and chlorophyll a. Be sure to
contrast what normally happens between the pigments and the effect of the thylakoid destruction.
3. Would you predict that the red fluorescence has more or less energy than the energy that was absorbed?
Explain your reasoning.
4. Using the card sort, arrange the colors in order from the highest energy level to the lowest energy level.
Record this arrangement
ACTIVITY 3: ABSORPTION OF CHLOROPHYLL
PRE-LAB QUESTIONS
1. What color is the chlorophyll solution?
2. Why is it this color?
Observe the chlorophyll solution under the UV light.
3. Is it still chlorophyll?
4. What is different? Why?
Essential Questions
1. What is the relationship between energy and wavelength that results the phenomenon of fluorescence?
2. Which wavelength(s) of light energy is absorbed by chlorophyll initiating the process of photosynthesis?
Name: ___________________________________ Date:__________________________________ Pd:__________
SPECTROPHOTOMETER DATA
WAVELENGTH
COLOR
ABSORBANCE
440
_______
_______
460
_______
_______
480
_______
_______
500
_______
_______
520
_______
_______
540
_______
_______
560
_______
_______
580
_______
_______
600
_______
_______
620
_______
_______
640
_______
_______
660
_______
_______
680
_______
_______
Graph Absorbance vs. Wavelength for the data that you collected.
Essential Questions
1. What is the relationship between energy and wavelength that results the phenomenon of fluorescence?
2. Which wavelength(s) of light energy is absorbed by chlorophyll initiating the process of photosynthesis?
Name: ___________________________________ Date:__________________________________ Pd:__________
ANALYSIS QUESTIONS
1. For which wavelengths is absorbance the greatest?
2. What colors are associated with these wavelengths?
3. What wavelength is not absorbed by the pigment solution?
4. What color is associated with this wavelength?
5. Predict which wavelengths would have a higher rate of photosynthesis. Explain your prediction.
6. The chlorophyll pigment converts light energy to food energy which is used by the plant for growth and
reproduction. Based on your data which wavelengths of light will be the most useful to the plant for this
purpose?
Essential Questions
1. What is the relationship between energy and wavelength that results the phenomenon of fluorescence?
2. Which wavelength(s) of light energy is absorbed by chlorophyll initiating the process of photosynthesis?