C3 cycle

1. C3 Cycle
Photosynthesis
 Photosynthesis means synthesis in the presence of light.
 Photosynthesis is a bio-chemical process in plant body where
carbohydrate is prepared in the presence of sunlight and chlorophyll
molecules by using water and carbon dioxide.
(or)
It is the anabolic process where the green plants of the plant body
synthesis their food and nutrient in the presence of sunlight.
Reaction
Sunlight
6CO2 +12H2O C6H12O6 + 6H2O + 6O2
Chlorophyll
Process of Photosynthesis
Photosynthesis process occurs in two different steps.
(a) Light reaction
(b) Dark reaction
Dark Reaction
 It is called as light non-requring reaction occurs in the presence of
carbon dioxide.
 It is enzymaties reaction which is temp sensitive.
 It is the process where the CO2 reduced into carbohydrate.
 Hence it is PCR Cycle (Photosynthetic Carbon Reduction).
 It is also known as Black Man’s reaction or Thermo-chemical reaction
or path of carbon in photosynthesis.
 On the basis of dark reaction 3 different ecological variant are
absorbed like.
1. C3 plant
2. C4 plant
3. C4M plant

2. C3 Plant
 Most of the plant species present on the earth surface belongs to C3
plants.
 1st product of dark reaction in this plant is a 3 carbon compound 3
PGA (3 phosphoglyceric acid)
 The cycle which operate in this plan known as C3 cycle or Calvin
cycle.
 The optimum temperature for operating this cycle is ranges between
10 - 25c.
Calvin Cycle/C3 Cycle
 It was 1st discovered by M. Calvin, A. Benson, J. Basshan (in 1961)
while working on radioactive isotope of carbon (C14) on chlorella
algae & scerdesmus.
 It is also known as BBC or Calvin Cycle or Calvin – Benson Cycle.
 Calvin and it’s co-worker used radio isotope carbon C14 in carbon
dioxide (C14O2) and trace the path of carbon in photosynthesis.
 Calvin Cycle or path of carbon during photosynthesis studied in 3 –
different step.
(1) Carboxylation
(2) Glycolytic reversal
(3) Regeneration of RUBP
 Here the CO2 acceptor is a 5 carbon compound known as RUBP
(Ribulose 1, 5 biphosphate).
 The RUBP can form 3 – phosphoglycenic acid (PGA) in presence of
water and most abundantprotein / enzymeRUBISCO (Ribulose -1, 5-
biphosphate carboxylase)
 Ellis in 1978
 PGA is reduced by a reducing power of NDPH2, for that reason it is
also known as reductive pen tosphophate cycle.
a. Carboxylation phase
b. Reduction/ Glycolytic reversal
c. Regeneration phase