Name ____________________________________ Date ____________ Period _____
Photosynthesis and Cellular Respiration
Chapter 5 - 2: Photosynthesis
Objectives
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Summarize how energy is captured from sunlight in the first stage of photosynthesis.
Analyze the function of electron transport chains in the second stage of photosynthesis.
Relate the Calvin cycle to carbon dioxide fixation in the third stage of photosynthesis.
Identify three environmental factors that affect the rate of photosynthesis.
Using the Energy in Sunlight
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The Stages of Photosynthesis
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Stage 1: Energy is captured from ___________________.
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Stage 2: Light energy is converted to __________________ energy, which is
temporarily stored in _______ and the energy carrier molecule _____________.
o Stage 3: The chemical energy stored in ATP and NADPH powers the formation
of __________________________________, using carbon dioxide, CO2.
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Photosynthesis can be summarized by the following equation:
6CO2 + 6H2O
Carbon dioxide water
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Photosynthesis
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Photosynthesis (Video Clip)
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C6H12O6 + 6O2
sugars
oxygen gas
Many organisms, such as plants, use sunlight to produce food in a process called
______________________________.
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In plant cells, photosynthesis takes place in structures called _______________.
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The chloroplasts _________ carbon dioxide, water and light energy to ________
sugar and oxygen.
Stage One: Absorption of Light Energy
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Sunlight contains a mixture of all the wavelengths
(colors) of visible light. When sunlight passes
through a prism, the prism separates the light into
different ________________ (ROY G BIV).
Pigments
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How does a human ______ or a leaf absorb light?
These structures contain light-absorbing
substances called ___________________.
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______________________ is the primary pigment
involved in photosynthesis
Chlorophyll a and b (Video clip)
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Chloroplasts contain pigments in flattened sacs
called _______________________.
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Why do plants appear green? ____________________________________________
____________________________________________________________________
Pigments
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The pigments that produce yellow and orange fall leaf colors, as well as the colors of
many fruits, vegetables, and flowers, are called __________________________.
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Carotenoids absorb wavelengths of light _________________ from those absorbed by
chlorophyll, so having both pigments enables plants to absorb more light energy during
photosynthesis.
Carotenoid (Video clip)
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Why do leaves appear red and yellow in the fall? _______________________________
______________________________________________________________________
______________________________________________________________________
Look at the diagram on the right or refer to
page 98 in your textbook for a color version
of the chart.
What colors of light does chlorophyll a absorb
best? ________________________________
Chlorophyll b? _________________________
Carotenoids? __________________________
Violet
Blue
Green
Yellow
Orange
Red
Production of Oxygen
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Clusters of pigments are embedded in the membranes of disk-shaped structures called
____________________________.
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When light strikes a thylakoid in a chloroplast, energy is transferred to ______________
in chlorophyll.
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This energy transfer causes the electrons to __________________________________
____________________. This is how plants first capture energy from sunlight.
Production of Oxygen
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The excited electrons that leave chlorophyll molecules must be ________________ by
other electrons.
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Plants get these replacement electrons from __________________ molecules, which
are split by an enzyme in the thylakoid.
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The oxygen atoms, O, from the disassembled water molecules combine to form oxygen
gas, O2.
Chloroplast
Parts of a Chloroplast
(Label)
Stage Two: Conversion of Light Energy
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Excited electrons that leave chlorophyll molecules are used to produce new molecules
that temporarily ____________________________________________.
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First an excited electron jumps to a nearby molecule in the thylakoid membrane. Then
the electron is passed through a series of molecules along the thylakoid membrane.
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The series of molecules through which excited electrons are passed along a thylakoid
membrane are called _________________ ________________ _______________.
Electron Transport Chains
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While one electron transport chain provides energy used to make ________, a second
electron transport chain provides energy used to make _______________.
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NADPH is an electron carrier that provides the high-energy electrons needed to make
carbon-hydrogen bonds in the third stage of photosynthesis.
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In this second chain, __________________________ combine with ________________
as well as an electron acceptor called NADP+, forming NADPH.
Electron Transport Chains of Photosynthesis
Electron Transport Chain
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When ___________________ is present, electrons pass from one molecule to the next
in an electron transport chain (ETC).
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As electrons flow through the ETC, hydrogen ions (H+) build up in the outer
compartment. This build up is similar to a charge in a __________________.
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The hydrogen ions help to make _______________.
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__________________________________ like NADH and FADH2 bring electrons to the ETC.
Converting Light Energy
to Chemical Energy
Stage Three: Storage of Energy
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In the third (final) stage of photosynthesis, carbon atoms from ____________________
in the atmosphere are used to make _____________________ compounds in which
chemical energy is stored.
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The transfer of carbon dioxide to organic compounds is called _____________________
____________________.
Calvin Cycle
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The Calvin cycle is a series of enzyme-assisted chemical reactions that produces a
____________________________:
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Step 1 Each molecule of carbon dioxide is added to a five-carbon compound by an
enzyme.
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Step 2 The resulting compound splits into two three-carbon compounds. Phosphate
groups and electrons are added to the compounds.
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Step 3 One of the resulting
three-carbon sugars is used to
make organic energy-storing
compounds.
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Step 4 The other three-carbon
sugars are used to regenerate
the initial five-carbon compound,
thereby completing the cycle.
(Video clip)
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Most plants fix _________________ in the Calvin cycle.
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First, a carbon dioxide molecule is added to a 5-C molecule, which immediately splits
into two 3-C molecules.
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A series of reactions converts the 3-C molecules into a 3-C sugar.
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___________ and __________ from Stage II of photosynthesis provide energy for
making the 3-C sugar.
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Some of the 3-C sugars leave the cycle and are used to __________________ the 5-C
molecule that starts the cycle.
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For every 3-C sugar that leaves the cycle, 3 carbon dioxide molecules are fixed.
Factors that Affect Photosynthesis
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Photosynthesis is directly affected by various environmental factors.
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In general, the rate of photosynthesis increases as light intensity increases until all the
pigments are being used.
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Photosynthesis is most efficient within a certain range of temperatures.
Environmental Influences on Photosynthesis
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As _______________________ increases the rate of photosynthesis increases and then
levels off to a plateau. This plateau represents the maximum rate of photosynthesis.
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Increasing levels of _____________________________ around a plant stimulates
photosynthesis until the rate of photosynthesis reaches a plateau.
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As __________________ increases, the rate of photosynthesis increases to a maximum
and then decreases with further rises in temperature.
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At a certain peak temperature, many _______________ become unstable and
ineffective.
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Stomata also close limiting _________________ and _____________________
____________ into the leaves.
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These conditions cause the rate of photosynthesis to decrease with the increase
in ______________________.