More than you ever wanted to know about Photosynthesis (part 1)

Light Dependent Reactions:Photosystem II and

Photosystem I

Energy Carrying Molecules

• ADP is converted into ATP by adding a phosphate group

• NADP+ is converted into NAPDH by adding two high energy electrons and a hydrogen ion (H+)

Low Energy Molecule Component added to energize molecule

High Energy Molecule

ADP Phosphate ATP

NADP+ 2 electrons and hydrogen ion (H+)

NADPH

Structure of Chloroplasts

Grana

Photosystem I• Pigments in photosystem I use light to energize

electrons.• Energized electrons are used to convert NADP+

to NADPH which is used to make glucose

Photosystem II• Pigments in photosystem II use light to energize an

electron and sent it into an electron transport chain.• Electrons sent to the ETC are replaced by splitting

water into two H+ ions, two electrons and one oxygen atom.

Electron Transport Chain• High energy electrons move from photosystem II to

photosystem I through an electron transport chain (series of enzymes)

• The energy from the electrons is used to pump H+ ions inside the thylakoid membrane.

ATP Synthase• The concentration gradient created by the

buildup of H+ ions inside the thylakoid is used to form ATP from ADP as H+ ions pass through an enzyme called ATP synthase.

Light Dependent Reactions