APBiologyLab4PlantPigmentsandPhotosynthesis生物学实验4植物色素和光合作用.doc

Student Worksheet  TITLE \* MERGEFORMAT AP Biology Lab 4: Plant Pigments and Photosynthesis PAGE 6  DOCPROPERTY Category \* MERGEFORMAT  PAGE 11 Name Period Date PAGE 1 AP Biology Lab 4: Plant Pigments and Photosynthesis, Converting Solar Energy to Chemical Energy Driving Questions How can the various photosynthetic pigments in plants be separated and visualized? Do rates of photosynthesis vary under different environmental conditions? “Different Conditions” = dark, and extreme heat (= boiling!) Why do rates of photosynthesis vary under different environmental conditions? Background Plants are photosynthetic organisms, able to harness light energy from the sun to convert carbon dioxide gas from the atmosphere into sugar through photosynthesis. 6CO2 + 6H2O + light energy ? C6H12O6 + 6O2 Chloroplasts, the organelles where photosynthesis occurs, contain pigments that absorb varying wavelengths of light. In the leaves of the plant, the pigments are indistinguishable, but they may be separated using chromatography. Paper chromatography separates a mixture into its various components. The mixture is placed onto a piece of chromatography paper and then a solvent is allowed to migrate (through diffusion) up the paper. As the solvent migrates it carries the components of the mixture along with it. Each of the components will migrate at varying rates based on their solubility, size and hydrogen bonding with the paper. The photosynthetic pigments absorb light energy from the sun. As light hits the chloroplasts electrons are excited and then passed along an elaborate electron transport chain within the thylakoid membrane of the chloroplasts. This electron flow does two things. It drives protons against their concentration gradient, setting up an electro-chemical gradient used for ATP synthesis; and it delivers electrons and protons to an electron acceptor, NADP+,, reducing the molecule to NADPH. (NADPH is then used to reduce CO2 to sugar