BISC 104 Principles of Biology PHOTOSYNTHESIS LAB PS What is it? Photo (use of light) Synthesis (to synthesize sugar, related biomolecules) Sunlight (Energy) is required because: 6 H2O + 6 CO2 C6H12O6 + 6 O2 Low energy High energy molecules molecules Why is PS Important? It produces Oxygen for all organisms It produces Food (carbohydrates) which is the base of all food chains It produces the C backbone for all biological molecules It removes CO2 from the atmosphere, off setting the greenhouse effect 1
Where does PS take place? Leaves cells with chloroplasts (with pigments) PS in the plant: The Raw Materials Water enters through roots CO2 enters through stomata in leaves Air spaces surround leaf cells Cross section of leaf (Microscope slide used by permission of Carolina Biological Supply Co.) Intercellular Air spaces Stomata 2
Cross section of leaf (Microscope slide used by permission of Carolina Biological Supply Co.) 2 Intercellular Air spaces &2 Stomata Cross section of leaf (Microscope slide used by permission of Carolina Biological Supply Co.) Intercellular Air spaces Stomata Cross section of leaf (Microscope slide used by permission of Carolina Biological Supply Co.) Intercellular Air spaces Stomata 3
Cross section of leaf (Microscope slide used by permission of Carolina Biological Supply Co.) Intercellular Air spaces Stomata Cross section of leaf (Microscope slide used by permission of Carolina Biological Supply Co.) Intercellular Air spaces Stomata Two Basic Reactions in PS Overall Reaction (abbreviated): Sunlight CO2 + H2O Æ Low energy 4
Two Basic Reactions in PS Overall Reaction (abbreviated): Sunlight CO2 + H2O ÆATP, NADPH ÆGlucose + O2 Low energy High energy High energy Intermediates Light-dependent reaction Sunlight Pigments Light-dependent reaction Sunlight Pigments H2O + ADP + NADP 5
Light-dependent reaction Sunlight Pigments H2O + ADP + NADP ÆATP + NADPH + ½ O2 High energy intermediates Light-dependent reaction Sunlight Pigments H2O + ADP + NADP ÆATP + NADPH + ½ O2 High energy intermediates Light-independent reaction (Calvin cycle) The synthesis part of photosynthesis: CO2 + NADPH + ATP Æ Glucose 6
Challenge Questions 1. What are ways to measure photosynthesis taking place? Challenge Questions 1. What are ways to measure photosynthesis taking place? 2. What factors affect the rate of photosynthesis? Ways to measure photosynthesis 7
Ways to measure photosynthesis Use of CO2 done in BISC207 labs Ways to measure photosynthesis Use of CO2 done in BISC207 labs Production of Glucose Ways to measure photosynthesis Use of CO2 done in BISC207 labs Production of Glucose Evolution of O2 this is basis of BISC104 experiment 8
Ways to measure photosynthesis Use of CO2 done in BISC207 labs Production of Glucose Evolution of O2 this is basis of BISC104 experiment Use of water What affects rate of PS? What affects rate of PS? 9
What affects rate of PS? Wavelengths of light (color) What affects rate of PS? Wavelengths of light (color) CO2 concentration What affects rate of PS? Wavelengths of light (color) CO2 concentration Type of leaf (plant) used 10
What affects rate of PS? Wavelengths of light (color) CO2 concentration Type of leaf (plant) used Age of leaf What affects rate of PS? Wavelengths of light (color) CO2 concentration Type of leaf (plant) used Age of leaf Temperature What affects rate of PS? Wavelengths of light (color) CO2 concentration Type of leaf (plant) used Age of leaf Temperature Available soil water 11
Lab 4 - Photosynthesis Uses O2 evolution to measure rate of light reaction (dependent variable) At different light intensities - (independent variable) Hypothesis The rate of photosynthesis, as measured by O2 evolution, will increase at higher light intensity and decrease at lower light intensity Theory behind Methods Discs are cut from leaves Leaf discs have air in them Air is pumped from air spaces in leaf, replaced with HCO3; discs sink As PS occurs, O2 is produced Air spaces fill up discs float 12
Theory behind Methods Rate of PS = How quickly do they float? What percentage float? Control do discs float in dark? (no PS) Results & Conclusions Collect Data Light None Low (room) Bright (lamp) # floating % floating Do Results Support Hypothesis? Additional Questions Did this experiment include the light independent reaction? What was purpose of bicarbonate? 13