Light Reaction

IB Bio Unit 5 SL year 1

2 halves of photosynthesis

light reaction, and calvin cycle

where light reactions occur in photosynthesis

in the thylakoids

Light Reaction description (Photosynthesis)

Uses photosynthetic pigments (ex chlorophyll) to absorb light, Splits H2O, releasing O2 as a byproduct, Produces ATP and NADPH for the Calvin Cycle

where the calvin cycle occurs

in the stroma

Calvin cycle description

Uses ATP and NADPH from the light reaction, Carbon fixation of CO2 from the atmosphere, Produces Sugars (glucose)

light reaction inputs

sunlight, water, ADP, NADP+

light reaction outputs

O2, ATP, NADPH

calvin cycle inputs

CO2, ATP, NADPH

calvin cycle outputs

sugars, ADP, NADP+

why plants do not convert CO2 into O2

plants dont absorb CO2 and produce O2, they are 2 separate processes. the oxygen produced was not the oxygen that was in the carbon dioxide

photosystems location

Integral protein complexes located within the phospholipid bilayer of the thylakoid membrane

type of molecules in photosystems

chlorophylls and other accessory pigments that will absorb light energy

how photosystems absorb light

Photons of light strike the pigment molecules within the photosystem, which creates excited electrons

electrons in pigment molecules that contain extra energy that is used to create ATP

excited electrons

photophosphorylation

the process of utilizing light energy from photosynthesis to convert ADP to ATP, which will go to power the calvin cycle. electrons are ultimately transferred to electron carriers.

electron carrier that becomes NADPH when it picks up 2 electrons

NADP+

photolysis

the process of using light energy to break water molecules in order to replace missing electrons in the photosystem, occurs in thylakoid space, O2 is created as a by product, electrons from H2O are transferred to the photosystem.