Transcript Calvin Cycle - Sacred Heart Academy

Calvin Cycle
2015 student
7.10 ATP and NADPH power sugar synthesis in the
Calvin cycle
• The Calvin cycle makes sugar in the stroma.
• The necessary ingredients are
– atmospheric CO2 and
– ATP and NADPH (from?)
• The Calvin cycle produces a three-carbon sugar
called glyceraldehyde-3-phosphate (G3P).
– Sugar formed from splitting glucose in glycolysis
• G3P is used to make glucose and other organic
molecules.
© 2012 Pearson Education, Inc.
Figure 7.10A
Input
CO2
ATP
NADPH
Calvin
Cycle
Output:
G3P
7.10 ATP and NADPH power sugar synthesis in the
Calvin cycle
• The steps of the Calvin cycle include
–
–
–
–
carbon fixation,
reduction,
release of G3P, and
regeneration of the starting molecule ribulose
bisphosphate (RuBP).
© 2012 Pearson Education, Inc.
Figure 7.10B_s1
1 Carbon
Step
fixation
Input:
3
CO2
Rubisco
1
3 P
6
P
RuBP
P
3-PGA
Calvin
Cycle
Figure 7.10B_s2
1 Carbon
Step
fixation
Input:
3
CO2
Rubisco
1
3 P
Step 2 Reduction
6
P
RuBP
P
3-PGA
6
ATP
6 ADP
Calvin
Cycle
2
6 NADPH
6 NADP
P
6
G3P
P
Figure 7.10B_s3
1 Carbon
Step
fixation
Input:
3
CO2
Rubisco
1
3 P
6
P
RuBP
Step 2 Reduction
P
3-PGA
6
ATP
6 ADP
Calvin
Cycle
Step 3 Release of one
molecule of G3P
2
6 NADPH
6 NADP
5
G3P
P
6
P
G3P
3
Output: 1
P
G3P
Glucose
and other
compounds
P
Figure 7.10B_s4
1 Carbon
Step
fixation
Input:
3
CO2
Rubisco
1
3 P
6
P
RuBP
Step 2 Reduction
P
3-PGA
6
ATP
3 ADP
6 ADP
Step 3 Release of one
molecule of G3P
Calvin
Cycle
4
3 ATP
4
Regeneration of RuBP
6 NADPH
6 NADP
5
P
6
P
G3P
Step
2
G3P
3
Output: 1
P
G3P
Glucose
and other
compounds
P
7.11 EVOLUTION CONNECTION: Other methods of
carbon fixation have evolved in hot, dry climates
• C3 plants
– First product of carbon fixation is a three carbon
compound 3-PGA
– Close their stomata in hot dry weather (why?)
– Photorespiration occurs
• Oxygen builds up, rubisco adds O2 instead of CO2 to
RuBP resulting in a 2-carbon product which is broken
down in the cell using ATP
– What will happen if this process continues for too
long?
© 2012 Pearson Education, Inc.
7.11 EVOLUTION CONNECTION: Other methods of carbon
fixation have evolved in hot, dry climates
• C4 plants have evolved a means of
– carbon fixation that saves water (closed stomata)
during photosynthesis
• C4 plants first fix CO2 into a four-carbon
compound.
– With the help of an enzyme
• The four- carbon compound “shuttles” the
carbon to the Calvin cycle.
© 2012 Pearson Education, Inc.
Figure 7.11
Mesophyll
cell
Bundlesheath
cell
CO2
4-C compound
4-C compound
CO2
CO2
Calvin
Cycle
Calvin
Cycle
3-C sugar
C4 plant
Sugarcane
CO2
Night
3-C sugar
Day
CAM plant
Pineapple
7.11 EVOLUTION CONNECTION: Other methods of carbon
fixation have evolved in hot, dry climates
• CAM plants, such as pineapples and cacti.
• CAM plants conserve water by opening their
stomata and admitting CO2 only at night.
• CO2 is fixed into a four-carbon compound,
– which banks CO2 at night and
– releases it to the Calvin cycle during the day.
© 2012 Pearson Education, Inc.