Carbon Fixation

Do the Calvin cycle reactions need light?

Yes

Where does C fixation take place?

Chloroplast thylakoid

Why the chloroplast thylakoid?

Because of availability of energy sources

What is the reducing power derived from?

NADPH

In what form is energy provided for C fixation?

ATP

How is the energy and reducing source regenerated?

From light via the photosystems

How much ATP is consumed to recycle ONE molecule of RuBP?

8/3

How much NADPH is consumed to recycle ONE molecule of RUBP

5/3

For every 3 RuBP molecules cycled how many molecules of CO2 are absorbed?

3

For every 3 RuBP molecules cycled how many C3 molecules are released from the cycle?

1

What is the largest molecule in terms of the number of carbon atoms within this cycle?

SuBP

Where is the RbcS gene located?

Nucleus

Where is the RbcL gene located?

Chloroplast

How does the nuclear-encoded Rbc subunit get into the chloroplast?

A signal sequence causes protein targeting

What problem would occur if Rubisco was active in the dark?

RuBP and other metabolites in the Calvin cycle would be run down to low levels so that photosynthesis would be slow to restart when needed.

What is the main purpose of the C2 cycle?

To regenerate RuBP

Why are three different organelles required for the C2 cycle?

Localisation of specialist enzymes

How can plants improve the ration of C3:C2 activity?

Open stomata

Concentrate carbon dioxide in the leaves