PhotosynthesisPhotosynthesis

Section 10.2Section 10.2

Leaf structureLeaf structure

Pigments and SunlightPigments and Sunlight

Chlorophyll reflects green and some blue and yellow Chlorophyll reflects green and some blue and yellow light while it absorbs the energy of all other colors of light while it absorbs the energy of all other colors of light.light.

Chemical EquationChemical Equation

In Photosynthesis carbon dioxide and water In Photosynthesis carbon dioxide and water are converted into glucose plus oxygen.are converted into glucose plus oxygen.

Light EnergyLight Energy ChloroplastChloroplast

6CO6CO22+6H+6H22O --- > CO --- > C66HH1212OO66 + 6 O + 6 O22

Light ReactionsLight Reactions

Dependent on light to power reactionsDependent on light to power reactions Occurs on the thylakoids in the chloroplastOccurs on the thylakoids in the chloroplast Consists of an Electron Transport Chain and Consists of an Electron Transport Chain and

PhotolysisPhotolysis This cycle powers and provides raw materials This cycle powers and provides raw materials

for the Calvin Cycle (Light Independent for the Calvin Cycle (Light Independent Reactions)Reactions)

HH22O +ADP + NADPO +ADP + NADP ATP +NADPH+H ATP +NADPH+H+ + +O+O22

Electron Transport ChainElectron Transport Chain

Light striking the chloroplast causes electrons Light striking the chloroplast causes electrons from within the chlorophyll to gain energy from within the chlorophyll to gain energy and leave the chlorophyll molecule. As these and leave the chlorophyll molecule. As these electrons move down the Electron Transport electrons move down the Electron Transport Chain (ETC) they lose energy which is used to Chain (ETC) they lose energy which is used to make ATPmake ATP

PhotolysisPhotolysis

The chlorophyll now picks up electrons from The chlorophyll now picks up electrons from water molecules. This splits water into water molecules. This splits water into hydrogen ions and oxygen gas given off by the hydrogen ions and oxygen gas given off by the plantplant

Hydrogen ions are picked up by NADPH and Hydrogen ions are picked up by NADPH and Form NADPH+HForm NADPH+H++ which are then carried to which are then carried to the Calvin Cycle (Light Independent reactions)the Calvin Cycle (Light Independent reactions)

PhotosynthesisPhotosynthesis

Calvin CycleCalvin Cycle

Take place in the Take place in the Stroma of the Stroma of the Chloroplasts Chloroplasts

Does not require light Does not require light can occur with or can occur with or without lightwithout light

1: Carbon Fixation1: Carbon Fixation

The joining of COThe joining of CO22 with other organic with other organic

molecules is called carbon fixation.molecules is called carbon fixation.

Step 1Step 1 6 CO6 CO22 combine with 6, 5 carbon compounds combine with 6, 5 carbon compounds

which are split to form 12 (3-PGA)which are split to form 12 (3-PGA)

2: Transfer of Energy2: Transfer of Energy

12 ATP and 12 NADPH transfer their energy 12 ATP and 12 NADPH transfer their energy to the 12 3-PGA to form 12 high energy to the 12 3-PGA to form 12 high energy molecules called G3Pmolecules called G3P

3: Sugar Production3: Sugar Production

2 of the G3P molecules will leave the cycle to 2 of the G3P molecules will leave the cycle to form a glucose molecule or another organic form a glucose molecule or another organic molecule.molecule.

4: Rubisco4: Rubisco

Rubisco is an enzyme that converts the Rubisco is an enzyme that converts the remaining 10 G3P molecules into 6, 5 carbon remaining 10 G3P molecules into 6, 5 carbon molecules called ribulose (RuBP)molecules called ribulose (RuBP)

CC44 Plants Plants

CC44 Plants can conserve water loss. Plants can conserve water loss.

The CThe C44 pathway plants fix CO pathway plants fix CO22 into a four into a four

carbon compound in the Calvin cycle instead carbon compound in the Calvin cycle instead of a 3 carbon molecule.of a 3 carbon molecule.

This molecule releases COThis molecule releases CO22 acting as a acting as a

delivery systemdelivery system This allows these plants to keep their stomata This allows these plants to keep their stomata

(plant cell pores) closed on hot days(plant cell pores) closed on hot days

CC44 Plants Plants

CAM PlantsCAM Plants

In water conserving plants like cacti COIn water conserving plants like cacti CO22 is is

taken in at night and bonded to an organic taken in at night and bonded to an organic substance so it can be used in the Calvin Cycle substance so it can be used in the Calvin Cycle without having to open their stomatawithout having to open their stomata

ChemosynthesisChemosynthesis

Process in which an autotroph obtains energy Process in which an autotroph obtains energy from inorganic compounds instead of Light.from inorganic compounds instead of Light.

Example deep ocean Hydro-thermal vents Example deep ocean Hydro-thermal vents supporting life on sulfur and decomposing supporting life on sulfur and decomposing bacteria bacteria