LAB 20. A.SANDERS

Pre-Lab Questions Describe how the functional units for beta carotene, xanthophyll, chlorophyll A, and chlorophyll B are different. Be sure to identify the subunits that adhere to paper during chromatography. Beta carotene - does not have any form of hydrogen bond; therefore, travels fur up the paper. Xanthophyll - contains oxygen group which forms hydrogen bond with the paper thus will not travel up the paper as far as beta carotene. Chlorophyll A - contains both oxygen and nitrogen which binds more stronger to the paper and therefore travels less than xanthophyll. Describe a technique for measuring photosynthetic rate. Using a light source to illuminate a plant that is placed under water. This is done at different distances from the initial test. You can then observe the rate at which gas is produced from each distance which tests the photosynthetic rate. Many deciduous trees have leaves that turn yellow in the fall. What do you suppose is happening in the leaves at the cellular and molecular level? There is a decrease in chlorophyll production within the leaves due to the environment change. This is caused by a decrease in the movement of nutrients throughout the tree due to the longer nights and shorter days in the fall/winter. Chloroplasts and mitochondria are both unusual in that they have double membranes and contain their own set of DNA. Can you think of any explanations for this observation? They have a symbiotic relationship. Experiment 1: Paper Chromatography Result Tables Table 1: Chromatography Data Solvent Distance from Original Line to Solvent Front Number of Bands Rf Factor Water 9cm 0 .40 Acetone 8cm 1 .70 Mineral Oil 6cm 2 .90 Acetic Acid 9cm 1 0 Table 2: Photosynthesis Data Test Tube Are chloroplasts present? Initial Color Final Color Time Required to Change Color (Hours) 1 Yes Green Yellow .5 hours 2 Yes Yellow Blue 12 hours 3 Yes Blue Dark blue 24 hours Post-Lab Questions What did the different colored bands signify in each solvent for Part 1? What pigments can you associate them with? Dark green/yellow green – chlorophyll yellow – xanthophyll orange - carotenes What is the osmolarity fluid used in Part 2? Why is this important? Why is it essential to keep it cool? Osmolarity fluid is used because the acids/organic solvent can change the osmolarity of the leaf due to the result of chromatogram paper observed. How could you modify this experiment to show the effects of different wavelengths of light on the photosynthetic rate? You could use different color lights or have test tubes sit different distances from the light. Some plants (grasses) tend to contain a greater concentration of chlorophyll than others (pines). Can you develop a hypothesis to explain this? Would it be testable? Different CO2 concentrations can interfere with the rate of photosynthesis. The more CO2, the more chlorophyll. Which makes this a testable hypothesis by measuring the amount of concentrated carbon dioxide and amount of chlorophyll in grasses and in pines. The difference in the amount of chlorophyll can be compared between the two plants and result can be noted.