PHOTOSYNTHESIS

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.)

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 photosynthesisIt 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 (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.

Photosynthesis

Photosystem II1. 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

The Calvin Cycle is powered by ATP (not shown)

Calvin Cycle1. 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)

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

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?