1. Photosynthesis

2. -the transfer of energy from sunlight to organic molecules -occurs in green plants, algae and some bacteria - involves a complex series of chemical reactions

3. Chloroplasts -the organelle in plants where photosynthesis takes place -double outer membrane -stroma (solution) - thylakoids (interconnected stacks of grana)

5. Sunlight -electromagnetic spectrum

6. Pigment - compound that absorbs light Chloroplast pigments: - chlorophylls (mostly a and b) - carotenoids (yellow, orange, brown) Accessory pigments (chlorophyll b, carotenoids)

8. Electron Transport The energy from sunlight is transferred from one molecule to another through electrons Photosystem - clusters of pigment molecules

9. Step 1: light is absorbed by chlorophyll a in photosystem II, which causes the electrons to be “excited” Step 2: excited electrons move to primary electron acceptor Step 3: excited electrons move through electron transport chain

10. Step 4: light is absorbed by chlorophyll in photosystem I, and excited electrons move through etc Step 5: excited electrons combine with NADP+ to form NADPH (will be used in next step

11. Chemiosmosis ATP is produced NADPH and ATP is used in the next part of photosynthesis - the Calvin Cycle

13. The Calvin Cycle Produces organic compounds using the energy from ATP and NADPH formed during the light reactions. The Calvin cycle “fixes” carbon from CO 2.

14. Step 1: CO 2 diffuses into the stroma. An enzyme combines a CO 2 molecule with a 5-carbon molecule (RuBP). The 6- carbon molecule splits into a pair of 3- carbon molecules (PGA)

15. Step 2: PGA is converted into PGAL using ATP and NADPH. Step 3: Some PGAL molecules can be used to make organic compounds

16. Equation for Photosynthesis 6CO 2 + 6H 2 O + light energy --> C 6 H 12 O 6 + 6O 2 Three turns of the Calvin cycle require nine ATP and six NADPH.

17. Mr. Durand Photosynthesis Song Photosynthesis Song

18. Alternative Pathways C3 plants - plant species that fix carbon exclusively through the Calvin cycle. C4 plants - plant species that fix CO 2 into four- carbon compounds - plants that partially close their stomata during the hottest part of the day -examples - corn, sugar cane, crabgrass

19. CAM plants - plant species that fix CO 2 at night when their stomata are open -grow fairly slowly -lose less water than C3 or C4 plants -examples - cactuses, pineapples

20. Rate of Photosynthesis Affected by: - light intensity - rate increases then levels off to a plateau - CO 2 levels - rate increases then levels off to a plateau - temperature - rate increases, peaks at a certain temp, then decreases