Photosynthesis Review Worksheet
Part A
Match the terms below with the correct description
Chlorophyll = C
Chloroplast = E
Electromagnetic spectrum
Electron transport chain = G
Grana
Light-dependent reactions = B
Light-independent reactions = I, J
Photosynthesis = H
Photosystem = F
Photon =A
Stroma = D
Thylakoid
a. __________________ packet of solar energy
b. __________________energy-capturing portion of photosynthesis that takes place
in thylakoid membranes of chloroplasts and cannot proceed without solar energy,
it produces ATP and NADPH
c. __________________green pigment that absorbs solar energy and is important in
photosynthesis
d. __________________ large, central compartment in a chloroplast that is fluid
filled and contains enzymes used in photosynthesis
e. __________________ membrane-bounded organelle with chlorophyll –
containing membranous thylakoids; where photosynthesis takes place
f. __________________Photosynthetic unit where solar energy is absorbed and
high-energy electrons are generated; contains a pigment complex and an electron
acceptor
g. __________________Passage of electrons along a series of carrier molecules
form a higher to a lower energy level; the energy released is used for the synthesis
of ATP.
h. __________________Process usually occurring within chloroplasts whereby
chlorophyll traps solar energy and carbon dioxide is reduced to a carbohydrate.
i. __________________ Series of photosynthetic reactions in which carbon dioxide
is fixed and reduced in the chloroplast.
j. __________________Synthesis portion of photosynthesis that takes place in the
stroma of chloroplasts and does not directly require solar energy; it uses the
products of the light dependant reactions to reduce carbon dioxide to a
carbohydrate
Part B
Answer the following questions
1. Explain the difference between autotrophs and heterotrophs. Give two examples of
each.
AUTOTROPH = make their own food, trees, flowers
HETEROTROPH = CAN NOT make their own food, humans, lemurs
2. What is ATP? How does it work?
ATP,adenosine triphosphate, is how cells store energy. It stores energy in the bonds
between phosphates. ATP is a short-lived molecule. When a phosphate group is
removed, energy is released. The molecule now contains two phosphates and is called
ADP.
3. Below draw a diagram of chloroplast and label the following: chloroplast membrane,
thylakoid, granum (grana), stroma, thylakoid membrane, thylakoid innerspace.
4. Explain why chloroplasts are green. (use the correct information from the
electromagnetic spectrum)
Chloroplasts contain chlorophyll and they absorb red and blue light, but reflect green
5. What is NADPH? What is the difference between NADP+ and NADPH? How does
NADP+ turn into NADPH?
NADPH = ELECTRON CARRIER
NADP+ IS THE REDUCED FORM OF NADPH AND TURNS INTO NADPH WHEN
IT RECEIVES HIGH ENERGY ELECTRONS
6. Write the chemical equation for the process of photosynthesis.
7. What are the reactants and products of Light Dependant Reactions? Where in the
chloroplast do they occur?
Reactants: WATER, LIGHT (ADP, NADP+)
Products: OXYGEN (ATP, NADPH, H+)
Location: THYLAKOID MEMBRANE
8. What are the reactants and products of Light-Independent Reactions? Where in the
chloroplast do they occur?
Reactants: CARBON DIOXIDE (ATP, NADPH)
Products: GLUCOSE (ADP, NADP+)
Location: STROMA
Part C
The Light Dependent Reactions of photosynthesis occur on the thylakoid membranes of
the chloroplast. Below is a diagram that describes the path of the electrons throughout the
L-D reactions. Use it to answer the next set of questions.
1. What is the ultimate source of energy in the L-D reactions? How is this energy
harnessed and transferred from one form to another?
The ultimate source of energy is photons (light energy) from the sun. This is captured by
chlorophyll in structures called photosystems. This energy is then transferred into high
energy electrons. These electrons are passed along the thylakoid membrane powering
reactions that create ATP and NADPH. ATP and NADPH are molecules that can store
energy for a longer period of time than electrons.
2. What is Cytochrome b6f? Why is it important? What do you think would happen
if Cytochrome b6f did not work?
Cytochrome b6f is a protein pump (active transport). It pumps H+ ions into the lumen
from the stroma against the H+ concentration gradient to create an area of very high
concentration of H+ ions in the lumen. These ions will then diffuse out of the lumen
through ATP synthase. The kinetic energy from this diffusion powers ATP synthase to
create ATP from ADP and Pi (single phosphate). If cytochrome b6f did not work, it
would take much longer to build up the concentration gradient of H+ ions.
3. When a water molecule is split, what is it split into? Where do all the resulting
components end up?
2 H+ stay in the lumen to build up a concentration gradient. ½ O2 (or 1 O which joins to
another O to form O2) Oxygen diffuses out of the chloroplast as a byproduct; 2e- go to
the PSII to replace the electrons that left after being excited by sunlight.
Part D
1. What are Light-Independent Reactions often called?
Calvin cycle
2. Why is there a need to go on with Light – Independent reactions? Why not stop
with the Light –Dependant Reactions since ATP and NADPH are energy carrying
molecules?
LID makes glucose, which has much more energy than ATP. Glucose can be broken
down by the mitochondria for WAY more energy. Glucose also is much more stable and
can store energy for much longer than ATP or NADPH.
3. Where does the Carbon Dioxide come from? What will happen to it and what will
it eventually become?
From humans, cars, etc and will enter through the stomata. It is converted into glucose
through the calvin cycle
4. How many molecules of carbon dioxide enter one Calvin Cycle? How many
molecules of high-energy sugars are produced as a result of one Calvin Cycle?
6 CO2 have entered and created 1 glucose
5. Look at the diagram below and complete it by filling in the products, reactants or
descriptions of what happens at each step.
See notes
6. Explain how temperature, intensity of light, and CO2 affect the rates of
photosynthesis?
See graphs from class
Part E
1. What is Chemosynthesis? Where do you find chemosynthesis?
Chemosynthesis is a system developed to harness the energy from chemicals such as
Hydrogen Sulfide (H2S) to create carbohydrates. These carbohydrates can then be
broken down to power the organisms’ functions. Chemosynthesis can be found at the
bottom of the ocean around hydrothermal vents.
2. Where do you find C4 plants?
C4 plants are found in hot, dry, arid environments like the desert.
3. What is the major problem that C4 plants have to address? How do they do so?
The major problem is that RuBP is capable of binding to Oxygen just as easily as Carbon
Dioxide. When Oxygen binds to RuBP, this is called photorespiration. Photorespiration
makes the RuBP useless and the cell can’t turn it into glucose. C4 plants have a special
anatomy to prevent Oxygen from coming into contact with RuBP. In C4 plants, CO2
initially binds to a 3-carbon molecule called PEP in the Mesophyll cell. This forms a 4carbon molecule called oxaloacetate. This molecule then leaves the mesophyll cell and
moves into a bundle sheath cell. Here, the CO2 can detach from oxaloacetate and attach
to RuBP to begin the Calvin Cycle normally.
4. How do CAM plants address this same problem that C4 plants have?
CAM plants only open up their stomata at night. This means that this is the only time
that they can take in CO2. They will convert this CO2 into Malic Acid which they store
in vacuoles. Then, during the day, they can remove the CO2 from the Malic acid and
attach it to RuBP, beginning the Calvin Cycle normally.