PhotosynthesisPhotosynthesis

The overviewThe overview

Photosynthesis

Light reaction Dark reaction

Photosystems 1 and 2 Calvin cycle

Needs H2O, light, NADP, ADP

Products are O2, NADPH, and

ATP

Needs CO2, NADPH,and ATP

Main product is glucose

Where does photosynthesis occur?Where does photosynthesis occur?

Leaves

Chloroplasts

Thylakoid

Thylakoid membrane

Picture of locationPicture of location

The steps to make NADPHThe steps to make NADPH

Sunlight delivers photons (light energy) Sunlight delivers photons (light energy) through chlorophyll in Photosystem IIthrough chlorophyll in Photosystem II

Chlorophyll passes this light energy until it Chlorophyll passes this light energy until it collides with an electroncollides with an electron

Electron is excited by extra energy and Electron is excited by extra energy and moves out of Photosystem IImoves out of Photosystem II

Electron is carried by proteins in the Electron is carried by proteins in the electron transport chainelectron transport chain

The steps for NADPH continuedThe steps for NADPH continued

Electron reaches photosystem I reaction Electron reaches photosystem I reaction center and runs out of energycenter and runs out of energy

Light energy is again passed through Light energy is again passed through chlorophyll in this area and hits the chlorophyll in this area and hits the electronelectron

Electron is excited again, passes through Electron is excited again, passes through another electron transport chain another electron transport chain

Electron finally reaches NADPElectron finally reaches NADP++ and and converts it to converts it to NADPHNADPH

Steps for OSteps for O22 ProductionProduction

Water enters thylakoid space at Water enters thylakoid space at photosystem II photosystem II

Water is split into electrons and protons Water is split into electrons and protons and Oand O22

Electrons replace those used in light Electrons replace those used in light reaction at photosystem IIreaction at photosystem II

Protons remain in space to be used for Protons remain in space to be used for ATPATP

OO22 is given off to atmosphereis given off to atmosphere

Steps to make ATPSteps to make ATP

Ion pumps force extra protons against Ion pumps force extra protons against concentration gradient to thylakoid space concentration gradient to thylakoid space to join those made when water was splitto join those made when water was split

Protons come back across the thylakoid Protons come back across the thylakoid membrane through protein channel called membrane through protein channel called ATP synthaseATP synthase

Protons join P with ADP to make Protons join P with ADP to make ATPATP