photosynthesis + water + energy glucose + oxygen carbon dioxide 6co 2 6h 2 o c 6 h 12 o 6 6o 2...
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Photosynthesis
+ water + energy glucose + oxygencarbondioxide
6CO2 6H2O C6H12O6 6O2light
energy + ++
Reactants Products
Review: Light reactions
• Convert solar energy to chemical energy
– ATP
– NADPH
• What can we do now?
energy
electron donator
build stuff !!
photosynthesis
ATP
The second phase of photosynthesis is called the Calvin Cycle (Light-Independent phase)
LIGHT-DEPENDENT PHASE (Requires Sunlight)
LIGHT-INDEPENDENT PHASE (Does Not Require Sunlight)
REMEMBER: This is when the chemical energy produced in the first phase is combine with Carbon Dioxide to create sugar.
LIGHT-INDEPENDENT REACTIONS/ Calvin Cycle
SUGAR ASSEMBLY- SECOND PHASE
The light-INDEPENDENT reactions (or Calvin cycle) use the chemical energy produced in the light-dependent reactions (ATP and NADPH) and carbon dioxide to
create sugar.
5
The Calvin CycleThe Calvin Cycle
STROMA
(Fluid interior)
The Calvin Cycle takes place in the stroma of the chloroplast.
Carbon Dioxide enters the plant leaf through openings called stomata.
THE CALVIN CYCLEAt the beginning of the Calvin Cycle, six CO2 molecules
bond with six 5-carbon sugar called RuBP (Ribulose Biphosphate) to form an six unstable 6-carbon sugar.
(An enzyme called Rubisco is responsible for joining these molecules.)
C C C C CCO
O
CARBON DIOXIDE
RuBP
C C C C C
C C C C C C
UNSTABLE 6-CARBON SUGAR
THE CALVIN CYCLEThis step is called Carbon Fixation, because a carbon is “fixed” onto the RuBP.
C C C C CCO
O
CARBON DIOXIDE
RuBP
C C C C C
C C C C C C
UNSTABLE 6-CARBON SUGAR
(CO2)
(RuPB)
THE CALVIN CYCLE
6 carbon sugar
THE CALVIN CYCLE
C C C C C C
UNSTABLE 6-CARBON SUGAR
C C C
C C C
The unstable 6-carbon sugars immediately split to form twelve stable 3-carbon molecules.
These molecules are called PGA’s (phosphoglycerate)
PGAs
(CO2)
(PGA)
(RuPB)
THE CALVIN CYCLE
6 Carbon sugar
3 Carbon molecules
THE CALVIN CYCLE12 NADPH and 12 ATP (from the light dependent
reactions) then give their energy to turn the 3-carbon PGA molecules into PGALs (3-carbon
sugars called glyceride tri-phosphate with higher energy bonds).
C C C
C C C
C C C
C C C2 PGAL molecules
NADPHATPADP + NADP+
ADP, P, and NADP+ are released and then return to the thylakoid membrane
to be re-energized.
(CO2)
ATP
ADP +
NADPH
NADP+
(PGAL)
(PGA)
(RuPB)
THE CALVIN CYCLE
6 carbon sugar
3 carbon molecules
(CO2)
ATP
ADP +
NADPH
NADP+
(PGAL)
(PGA)
(RuPB)6 carbon sugar
3 carbon molecules
(2 PGAL)
(Sugar)
2 PGALs are transferred out of the chloroplast to the cytoplasm of the cell where they are combined to make a
six-carbon glucose.
(CO2)
ATP
ADP +
ADP +
(Sugar)
NADPH
NADP+
(PGAL)
(PGAL)
ATP
(RuPB)6 carbon sugar
3 carbon molecules
The ten remaining PGAL molecules each with 3-carbon atoms, reorganize using 6 ATP molecules to make 6 molecules of RuBP (the 5-carbon sugar) to start the
cycle all over again.
Question 3 A molecule of adenosine that has two
phosphate groups bonded to it is ______.
A. AMP
B. ADP
C. ATP
D. ACP
The answer is B. ADP is adenosine diphosphate.
Adenosine
Adenosine
P P P
P
P
P P
Adenosine triphosphate (ATP)
Adenosine diphosphate (ADP)
Question 4 What is the function of the protein molecule
shown in this diagram?
ATP
ADP
ADP
Protein P Energy
This protein molecule has a specific binding site for ATP. In order to access the energy stored ATP, the protein molecule binds the ATP and uncouples one phosphate group. This action releases energy that is then available to the cell.
ATP
ADP
ADP
ProteinP Energy
The function accomplished by the light-dependent reactions is ________.
Question 6
D. conversion of sugar to PGAL
C. carbon fixation
B. sugar production
A. energy production
The answer is A. The light-dependent reactions transfer energy from the sun to chlorophyll, and pass energized electrons to proteins embedded in the thylakoid membrane for storage in ATP and NADPH molecules.
Sun
Chlorophyll passes energy down through the electron transport chain.
for the use in light-independent reactions
bonds P to ADP
forming ATPoxygen
released
splitsH2O
H+
NADP+
NADPH
Light energy transfers to chlorophyll.
Energized electrons provide energy that
The first step in the Calvin cycle is the ________.
Question 7
D. Bonding of carbon dioxide to RuBP
C. Splitting of six-carbon sugar into two three-carbon molecules
B. production of PGAL
A. replenishing of RuBP
The answer is D. The carbon atom from CO2 bonds with a five-carbon sugar to form an unstable six-carbon sugar. This molecule then splits to form two three-carbon molecules.
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Photosynthesis Photosynthesis OverviewOverview
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