204 ^|

A Handbook of Biology

ADP

ATP

Calvin cycle

ATP

+

NADPH

ADP

+

P + NADP

i

+

Sucrose, starch

Regeneration

Carboxylation

3-phosphoglycerate

Reduction

Ribulose–1,5

–bisphosphate

Triose

phosphate

1

2

3

Atmosphere

CO + H O

2

2



It is a series of reactions

leading

to

the

glucose

formation.



Here, 2 ATP molecules for

phosphorylation

and

two

molecules

of

NADPH

for

reduction per CO2 molecule

are used. (AIPMT 2005)



Fixation of 6 CO2 molecules

and 6 turns of the cycle are

needed for the formation of

one glucose molecule from

the pathway. (AIPMT 2005)

02

RËDÜÇTÏØÑ

RËGËÑËRÅTÏØÑ ØF RÜBP



It is crucial for continuation of the cycle.



It requires one ATP for phosphorylation to form RuBP hence, for

every CO2 molecule, 3 ATP molecules and 2 NADPH molecule are

required.



It is probably to meet this difference in number of ATP and NADPH

used in the dark reaction that cyclic phosphorylation takes

place.



To make 1 glucose molecule, 6 turns of the cycle are needed

03

WHÅT GØËS ÏÑ ÅÑD ÇØMËS ØÜT ØF THË ÇÅLVÏÑ ÇÝÇLË?

In

Out

6 CO2

1 glucose

18 ATP

18 ADP

12 NADPH

12 NADP