Metabolites of the calvin cycle these atp and nadph

Metabolites of the Calvin Cycle
These ATP and
NADPH molecules
were produced by
the light reactions.
3 ADP + 3
P
6 ADP + 6 P
These ATP
molecules were
produced by the
light reactions.
net gain of one G3 P
Glucose
CO
2
fixation
CO2
reduction
regeneration
of RuBP
intermediate
6 NADPH
+
5 G3P
C
3
3 RuBP
C
5
6 G3P
C
3
6 BPG
C
3
3 CO
2
Other organic molecules
6 NADPH
3
ATP
6
ATP
Calvin cycle
6 3PG
C
3
3 C
6
CH
2
O
stroma
H
2
O
CO
2
ADP + P
NADPH
NADP +
ATP
O
2
2
solar
energy
Light
reactions
Calvin
cycle
From our text -

Calvin Cycle Reactions: Carbon Dioxide
Reduction
NADPH NADP
+
ATP
3PG
G3P
BPG
ADP +
P
As 3PG becomes G3P, ATP becomes
ADP + and NADPH becomes NADP
+
P
 3PG is reduced to BPG
 BPG is then reduced to G3P
 Utilizes NADPH and some ATP produced in the light reactions

Calvin Cycle Reactions: Regeneration of RuBP
As five molecules of G3P become three
molecules of RuBP, three molecules of ATP
become three molecules of ADP +
3 ATP
5 G3P 3 RuBP
3 ADP + P
P
 RuBP used in CO
2
fixation must be replaced
 Every three turns of Calvin Cycle,

Five G3P (a 3-carbon molecule) are used (5 x 3 = 15 C)

To remake three RuBP (a 5-carbon molecule) (3 x 5 = 15 C)

5 X 3 = 3 X 5

Importance of the Calvin Cycle
 G3P (glyceraldehyde-3-phosphate) can be
converted to many other molecules

The hydrocarbon skeleton of G3P can form

Fatty acids and glycerol to make plant oils

Glucose phosphate (simple sugar)

Fructose (which with glucose = sucrose)

Starch and cellulose

Amino acids

C
4
Photosynthesis
 In hot, dry climates

Stomata must close to avoid wilting

CO
2
decreases and O
2
increases

O
2
starts combining with RuBP,
leading to the production of CO
2

Called
photorespiration
 C
4
plants solve the problem of photorespiration

Fix CO
2
to PEP (a C
3
molecule)

The result is oxaloacetate, a C
4
molecule

In hot & dry climates

C
4
plants avoid photorespiration

Net productivity is about 2-3 times greater than C
3
plants

In cool, moist environments, C
4
plants can’t compete with C
3
plants

Photosynthesis – C
4
pathway
•
CO
2