photosynthesis

Photosynthesis

The process in which light energy is transformed into chemical energy

Performed by Producers such as Plants Algae some Protists (eg:

Phytoplankton)

It is a complex series of reactions that can be summarised as:

6CO2 + 6H2O C6H12O6 + 6O2

or

6CO2 + 12H2O C6H12O6 + 6O2 + 6H2O

Photosynthesis Overview6H2O + 6 CO2 --> C6H12O6 + 6 O2

Light Dependent StageH2O --> O2

requires Light E

Light Independent StageCO2 --> 2x3C sugars

ChloroplastsFlat shape provides a large surface

area exposed to sunlightMany stomata on one or both leaf

surfaces provides access to CO2

Thinness and presence of air spaces in leaves enable diffusion

Xylem vessels transports water to cells

Many chloroplasts to trap lots of energy

Draw and label chloroplast

Light-dependent stageOccurs in GranaNeeds water and light energye- that is absorbed is used to:

◦Produce ATP◦Split H20 molecules (2H+ and O)

NADP is a carrier/acceptor molecule that gathers H+ ions

ATP and NADPH are used in next stage (light-independent stage)

Inputs Outputs

Water H2O ATP

Electron e- NADPH

NADP+

ADP + POxygen (“waste”)

Light-independent stageOccurs in StromaDoes not need light but NADPH and

ATP from previous stageNeeds CO2 and H+ ions Sugar molecules are synthesised from

CO2

CO2 = oxidised state (low E compound)

C(H2O)n = reduced state (high E compound)

NADPH (carrier H+) is the reducing agentATP is the energy source

Inputs Outputs

ATP ADP + P

NADPH NADP+

CO2 3C (PGAL) -> Glucose

Carbon reduction in C3 Plants

Calvin Cycle

=PGAL

Carbon reduction in C4 plantsPlants in hot,

dry habitats and important crop plants such as corn, sugar cane

One step before Calvin cycle:

Putting Photosynthesis together