Download PHASE ONE: LIGHT REACTIONS

PHASE ONE: LIGHT-DEPENDENT REACTIONS
Photosystem II (in thylakoid membrane)
 Light excites electrons
 Water is split into H+ and O2
o O2 leaves as waste
o H+ stays inside of grana
 Passes electron on to Photosystem I
Photosystem I (in thylakoid membrane)
 Light excites electrons
 Is constantly being feed electrons from photosytem II
 Electron is passed on to Ferrodoxin
Ferrodoxin (in thylakoid membrane)
 Transfers electron to NADP+
 NADP+ combine with H+ to form NADPH
o This happens outside of the thylakoid membrane, in the stroma.
o NADPH is a energy storing chemical used later in photosynthesis
ATP Synthase
 The concentration of H+ builds up inside the grana.
 ATP Synthase opens a channel, and H+ rushes through the channel, through the thylakoid membrane, to
the stroma.
 This converts ADP (adenosine di-phosphate) to ATP (adenosine tri-phosphate)
o This happens in the stroma, outside of the thylakoid membrane
PHASE TWO: LIGHT INDEPENDENT REACTIONS, CALVIN CYCLE
Step 1
 6 CO2 molecules from the atmosphere combine with 6 RuBP molecules
o CO2 has 1 carbon: 6 X 1 = 6 total carbons
o RuBP has 5 carbons: 6 X 5 = 30 total carbons
o 30 + 6 = 36
 This makes 12 molecules of 3-PGA
o 3-PGA has 3 carbons: 12 X 3 = 36 total carbons
Step 2
 The 12 molecules of 3-PGA are converted to 12 molecules of G3P.
 Energy is required to do this.
o It comes from 12 ATP molecules and 12 NADPH molecules.
o They are reduced to 12 ADP molecules and 12 NADP+ molecules
 G3P also has 3 carbons: 12 X 3 = 36
Step 3 (Rubisco)
 The enzyme rubisco removes 2 molecules of G3P to be used to make sugars.
 The other 10 molecules of G3P are converted back into 6 molecules of RuBP.
 Starting: G3P: 12 X 3 = 36 carbons
 Ending: G3P: 2 X 3 = 6 carbons
RuBP: 6 X 5 = 30 carbons
 30 + 6 = 36