PhotosynthesisChapter 8

Trophs

• Autotrophs

• Heterotrophs

The Meaning of Life…

Photosynthesis

6CO2 + 6H2O C6H12O6 + 6O2

• Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high-energy sugars and oxygen.

• Green things are generally understood to be photosynthesizers

Chlorophyll• Chlorophyll a

• Chlorophyll b

• Pigments that absorb varying frequencies of light.

• Poor absorbers of blue-green frequency

Chloroplasts

• Thylakoids- contain photosystems which are the light-collecting units

• Sunlight excites electrons in the chlorophyll which are then passed to electron carriers

(Sound familiar?)

• NADP+ is charged with an electron to form NADPH

Light Dependent Reactions

Light Dependence

• Two reactions are considered light-dependent in photosynthesis

• Photosystem II absorbs light and produces energized electrons, H+ ions, and water.

• Photosystem I receives tired electrons from II, are re-energized by sunlight, and used to make NADPH which passes to Calvin.

Mr. Calvin

• ATP and NADPH from the light-dependent reactions are used by the Calvin Cycle to create sugars.

Factors Affecting Photosynthesis

• Water availability

• Sunlight intensity

• Temperature (photosynthetic enzymes function best from 0-35 degrees C)

• Light Wavelength

Back and Forth

6CO2 + 6H2O C6H12O6 + 6O2

light

CO2 + H2O

O2 + sugar