Photosynthesis

Light Reactions: Trapping Energy Takes place in the stacks of thylakoids (grana) inside the chloroplast Thylakoid Grana

Steps in the Light Reaction Light strikes the electrons in chlorophyll Electrons: Absorb energy Leave the chlorophyll molecule Are caught and passed down the Electron Transport Chain Lose energy Energy is stored as ATP.

Steps in the Light Reaction At the same time: 4. Chlorophyll picks up an e- from water 5. Causes water to split  2H + and O (photolysis) 6. Freed H + ions are picked up by NADP+  NADPH + H+ (coenzyme) 7. Oxygen is given off as a waste product

Other Points Light reactions are really three separate reactions. Energy absorption ETC Splitting of water ATP and NADPH are not stable enough for long term energy storage.

Summary (put in margin) Starts with: Light and water Produces: NADPH ATP O2 Takes place in the: Thylakoids /grana

Calvin Cycle: Making Sugar Takes place in the stroma which surrounds the grana Uses the stored energy of the light reaction

Steps in the Calvin Cycle C (from CO2) is added to a reusable 5C molecule by the enzyme, rubisco. (carbon fixation) 2. Unstable 6C molecule breaks down into two 3C molecules (PGA) 3. Hydrogen from NADPH and energy from ATP is used to make stable molecules 3C molecules + NADPH + ATP  stable 3C + NADP+ + ADP + P

Steps in the Calvin Cycle 4. Repeated 6 times. 5. Eventually two 3C molecules are removed from cycle and used to make glucose. (can also make other sugars) 6. Remaining 3C molecules are converted back into the 5C molecule that originally picked up the C

Summary (put in margin) Starts with: CO2 (air) NADPH ATP Reusable 5 C molecule Produces: Glucose ADP + P NADP+ Takes place in the: stroma

Factors that affect rate of photosynthesis Amount of water Light intensity Temperature Presence of minerals

H2O CO2 Light NADP ADP Calvin Cycle (stroma) Light Reactions grana ATP NADPH Other products O2 Glucose