By C Kohn, Waterford, WI

Photosynthesis (in a nutshell)  The energy originally from sunlight is transformed and used to combine CO 2 and H 2 O into Glucose (C 6 H 12 O 6 ) or other plant molecules (cellulose, amino acids, etc.)

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.

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.

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

Photosynthesis  Photosynthesis has two components: A) Photosystem II ○ 1. The absorption of sunlight and water (H 2 O) ○ 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 CO 2 ○ 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.

Photosynthesis

Photosystem II 1. Sunlight (primarily red & blue wavelengths) is absorbed by chlorophyll pigments in the chloroplasts. Water (H 2 O) is absorbed by the chloroplast 2. The sunlight is used to separate hydrogen from oxygen. Oxygen is released as O 2. 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 P i Click for explanations

The Calvin Cycle is powered by ATP (not shown) Calvin Cycle 1. CO 2 is absorbed. Carbon is separated from oxygen. O 2 is released. 2. The remaining carbon atom is combined with 5- carbon Rubisco (from the previous cycle) Click for explanations G3P’s on their way to becoming glucose. 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. Rubisco, re-created and ready to bind to the carbon in CO2

Photosynthesis (PSII & Calvin)

Research  Regulation of photosynthesis in developing leaves of soybean chlorophyll-deficient mutants Cai-Zhong Jiang, et al, Iowa State Univ Regulation of photosynthesis in developing leaves of soybean chlorophyll-deficient mutants  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?

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?

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?

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?