PHOTOSYNTHESIS Chapter 7 creating energy-rich organic molecules from light PHOTOSYNTHESIS The photosynthesis rxn is: anabolic (building) endergonic (energy-storing) redox

PHOTOSYNTHESIS Summative equation

LIGHT Electromagnetic (aka radiant) energy Long wavelength Low frequency Low energy Short wavelength High frequency High energy Photosynthesis employs visible light wavelengths

Light Energizes Electrons e- absorb specific wavelengths e- jump to more distant orbit fall back, emitting light & heat Look familiar? http://www.worsleyschool.net/science/files/electronphoton/interaction.html http://student.ccbcmd.edu/~gkaiser/biotutorials/photosyn/photon.html

Light Energizes Electrons to ETC If the excited e- are in chlorophyll, or other plant pigments, the e- doesn’t fall back - it gets transferred to an electron transport chain http://student.ccbcmd.edu/~gkaiser/biotutorials/photosyn/photon.html

Pigments Absorb Different Wavelengths • In plants, chlorophyll a is the primary pigment, unable to absorb (thus transmitting) green • In fall, chlorophyll production stops and accessory pigment transmission is visible - yellow, reds, until production stops

Wavelength Is Key to Psn Productivity Photosynthetic rate is greatest at red, blue wavelengths

Granum - stack of thylakoids CHLOROPLASTS contain CHLOROPHYLL and other PIGMENTS Light Reflected Absorbed light Granum - stack of thylakoids Transmitted Stacking pigments maximizes absorption Analgous to a multijunction solar cell Light passing through is trapped by pigments in next thylakoid - except green!

Pigments are Within in the Thylakoid Membrane

Pigments are Grouped into Photosystems • Accessory pigments shuttle energy, in form of excited e-, to the reaction center, containing chlorophyll a • Focuses the energy, like an antenna

Photosynthesis labs Chromatography Leaf disc assay Spectrometry Uses the distance the pigments travel in solvent to differentiate between them Photosynthesis labs Leaf disc assay As O2 is produced in psn, the discs rise carotene xanthophyll chlorophyll Show Bozeman video on labs Spectrometry • chlorophyll electrons, excited by light, are captured by a blue dye turning the solution lighter in the process • the more excited the electrons, the quicker the solution loses color, and the more light is transmitted through the sample.