IMPORTANT “PLAYERS” IN

PHOTOSYNTHESIS

IMPORTANT “PLAYERS” IN

PHOTOSYNTHESISElectrons

CO2

H2OSunlight (Photons)

ElectronsCO2

H2OSunlight (Photons)

• Electron Carriers (Shuttle buses)

• NADPH• ATP, ADP, P• Photosystems I & II

• Electron Carriers (Shuttle buses)

• NADPH• ATP, ADP, P• Photosystems I & II

Where is all this happening?

Where is all this happening?

• The Chloroplast

2 parts-----1) Thylakoid membranes-- Stacks of thylakoids are

grana 2) Matrix--The soupy inside

of the chloroplast

• The Chloroplast

2 parts-----1) Thylakoid membranes-- Stacks of thylakoids are

grana 2) Matrix--The soupy inside

of the chloroplast

Photosynthesis-->2 StagesPhotosynthesis-->2 Stages

• I. Light Reaction-->4 parts• II. “Dark” Reaction-->4 steps

• I. Light Reaction-->4 parts• II. “Dark” Reaction-->4 steps

Light ReactionLight Reaction

• 1) Light Absorption• 2) Electron Transport• 3) Oxygen Production• 4) ATP formation

• 1) Light Absorption• 2) Electron Transport• 3) Oxygen Production• 4) ATP formation

1) Light Absorption1) Light Absorption

• Light is absorbed by a photosystem on the thylakoid membranes

• Light is absorbed by a photosystem on the thylakoid membranes

• (A photosystem contains clusters of chlorophyll molecules & accessory pigments)

• (A photosystem contains clusters of chlorophyll molecules & accessory pigments)

• The electrons of the chlorophyll are excited by sunlight and stripped off, raising them to a higher energy level (To do work) where they are passed to electron carrier molecules

• The electrons of the chlorophyll are excited by sunlight and stripped off, raising them to a higher energy level (To do work) where they are passed to electron carrier molecules

2) Electron Transport2) Electron Transport

• The high energy electrons (The excited ones) are passed along a series of electron carriers (proteins in the membrane)

• The carriers are known as the ETC (Electron Transport Chain)

• The high energy electrons (The excited ones) are passed along a series of electron carriers (proteins in the membrane)

• The carriers are known as the ETC (Electron Transport Chain)

• At the end of the ETC, the high energy electrons are passed to their final destination NADP+

• At the end of the ETC, the high energy electrons are passed to their final destination NADP+

NADP+ + H+ + 2e- --->NADPHNADP+ + H+ + 2e- --->NADPH

(NADPH is our carrier molecule, it carries electrons e- and Hydrogens H+)

(NADPH is our carrier molecule, it carries electrons e- and Hydrogens H+)

3) Oxygen Production3) Oxygen Production

• The electrons that were stripped from the chlorophyll are paid back to the original chlorophyll molecule, from the splitting of H2O. (Photolysis)

• 2H20---> O2 + 4H+ + 4e-s

• The electrons that were stripped from the chlorophyll are paid back to the original chlorophyll molecule, from the splitting of H2O. (Photolysis)

• 2H20---> O2 + 4H+ + 4e-s

4) ATP Formation4) ATP Formation

• When H2O is split, the H+’s are released inside of the thylakoid membrane.

• As e-’s are passed from chlorophyll to NADP+, more H+’s are pumped across the membrane. The inside becomes more positively charged.

• When H2O is split, the H+’s are released inside of the thylakoid membrane.

• As e-’s are passed from chlorophyll to NADP+, more H+’s are pumped across the membrane. The inside becomes more positively charged.

• This Condition sets the stage for the chemiosmosis of H+ ions. (high-->low)

• H+ ions can pass through a special protein enzyme port (ATP Synthase) that attaches a phosphate to ADP forming ATP

• This Condition sets the stage for the chemiosmosis of H+ ions. (high-->low)

• H+ ions can pass through a special protein enzyme port (ATP Synthase) that attaches a phosphate to ADP forming ATP

ATP SYNTHASEATP SYNTHASE

The Dark Reaction (Calvin Cycle) Step 1The Dark Reaction

(Calvin Cycle) Step 1• 3 CO2

molecules enter the cycle

• Each join with a 5 carbon RUBP and split-->Into 6 3 carbon PGA

• 3 CO2 molecules enter the cycle

• Each join with a 5 carbon RUBP and split-->Into 6 3 carbon PGA

Calvin cycle Step 2Calvin cycle Step 2

• The 6 molecules of PGA change into 6 molecules of PGAL

• (ATP & NADPH is used for this)

• 1 PGAL is used to make glucose

• The 6 molecules of PGA change into 6 molecules of PGAL

• (ATP & NADPH is used for this)

• 1 PGAL is used to make glucose

Step 3 Regeneration of RUBP

Step 3 Regeneration of RUBP

• The remaining 5 are used to make RUBP (A 5 carbon molecule)

• RUBP is regenerated by re-arranging the remaining 5 PGALS

• The remaining 5 are used to make RUBP (A 5 carbon molecule)

• RUBP is regenerated by re-arranging the remaining 5 PGALS