Photosynthesis

1. By C Kohn, Waterford, WI Photosynthesis

2. Photosynthesis (in a nutshell) • The energy originally from sunlight is transformed and used to combine CO2 and H2O into Glucose (C6H12O6) or other plant molecules (cellulose, amino acids, etc.)

3. Structures • Photosynthesis occurs only in plants and a small number of single-celled organisms (like algae). • To be able to photosynthesize, you must have a specific organelle: the Chloroplast.

4. Chloroplasts • Inside each chloroplast are what look like stacks of green pancakes. • Each pancake is called a thylakoid. • The stacks of thylakoids are known as grana. • The empty space inside the chloroplast is called the stroma.

5. Chlorophyll • Each chloroplast’s thylakoids are lined with a special sun-absorbing pigment. • This pigment is known as chlorophyll. • It is what allows the plant to absorb sunlight which is used to power photosynthesis • It also is what makes the plant green. • Chloroplasts use red & blue light and reflect green

6. Photosynthesis • Photosynthesis has two components: • A) Photosystem II • 1. The absorption of sunlight and water (H2O) • 2. The removal of hydrogen atoms from water using the energy of sunlight • 3. The use of this hydrogen to power ATP production in each thylakoid’s ATP Synthase. • B) The Calvin Cycle • 1. The absorption of CO2 • 2. The use of ATP to power the production of G3P from CO2 and Rubisco (5 carbon molecule) in the stroma. • 3. The use of G3P to make sugars, amino acids, fats, and all other components of the plant.

7. Photosynthesis

8. Photosystem II 1. Sunlight (primarily red & blue wavelengths) is absorbed by chlorophyll pigments in the chloroplasts. Water (H2O) is absorbed by the chloroplast 2. The sunlight is used to separate hydrogen from oxygen. Oxygen is released as O2. H+ is stored in each thylakoid. 3. The hydrogen absorbed by the thylakoid is used to power ATP Synthase, which makes ATP from ADP and Pi Click for explanations

9. The Calvin Cycle is powered by ATP (not shown) Calvin Cycle 1. CO2 is absorbed. Carbon is separated from oxygen. O2 is released. 2. The remaining carbon atom is combined with 5-carbon Rubisco (from the previous cycle) 3. The 6-carbon molecule is split into two 3-carbon molecules (G3P). One G3P is used to make sugars or other plant molecules. The other is paired with 2 carbon atoms to re-make Rubisco. G3P’s on their way to becoming glucose. Rubisco, re-created and ready to bind to the carbon in CO2 Click for explanations

10. Photosynthesis (PSII & Calvin)

11. Research • Regulation of photosynthesis in developing leaves of soybean chlorophyll-deficient mutantsCai-Zhong Jiang, et al, Iowa State Univ • This team used soybeans that were missing one gene (out of two genes total) for chlorphyll production. • These plants were lighter green than the control. Why?

12. Research • Jiang created the plants through genetic crosses. • ¼ of the plants were dark green (normal), ½ were light green, and ¼ were yellow. The yellow plants always died. • Why were some yellow? • Why did the yellow always die?

13. Research • Jiang’s team also found that plants with half as much chlorophyll produced half as much Rubisco. • Why might this be? Why would this be good for a plant?

14. Mr. Kohn’s Research • In the Agriscience Lab, Mr. Kohn and students studied whether or not changing the color of water will reduce the growth of seaweed. • How would the color of water affect the seaweed’s growth? (Note: how does color affect photosynthesis?) • What colors might be most effective?