AP Bio Photosynthesis Lab

Light Dependent Reactions Photosynthesis is the process of turning solar energy into chemical energy using chloroplasts in an autotroph. When photons from the sun reach a plant leaf some color wavelengths are absorbed and others are reflected. This process starts at the light dependent reactions inside the thylakoids in the chloroplast. The thylakoid membrane contains an electron transport chain that contains clusters of molecules to capture the photons. The first cluster of pigments is known as photosystem II, contains chlorophyll a, and captures red and purple best but yellow and green worst. The light that comes in excites electrons and causes photolysis. Oxygen diffuses out as a waste product and Hydrogens create a gradient inside the thylakoid. This gradient causes the ions to flow out through the ATP synthase from high to low concentration turning the molecular motor attached the the integral channel as the ions flow through. ATP Synthase physically attaches an inorganic phosphate (pi) to an ADP to create the energy molecule ATP. This energy is used by the Calvin cycle in the light independent reactions. Light Independent Reactions The light independent reactions occurs in the stroma as carbon dioxide enters the chloroplast and gets ripped apart into carbon and oxygens. These are going to attach to hydrogens so that glucose (C6H12O6) can be created and released. Where did those 6 hydrogens come from? The hydrogens that ran through the ATP synthase from inside the thylakoid to the stroma are transported over from the thylakoid. Transport molecules (called NADP+) carry a hydrogen and two electrons over to the Calvin cycle. This molecule is powered by the second cluster of pigments, the photosystem I, which contains chlorophyll b. When photons hit this cluster it powers the NADP+ to physically pick up the H and two electrons. When this molecule is full it is called NADPH and after it drops off its hydrogen and electrons it returns to the thylakoid to refill again. Cyclic and NonCyclic Photophosphorylation The electron transport chain in the thylakoid membrane contains photosystem II and photosystem I. Photosystem II comes first and is charged by photons producing ATP. Photosystem I comes next and is charged by photons producing NADPH. This is non-cyclic photophosphorylation... it's a linear process where the photons hit PSII to make ATP and move on to excite PSI to make NADPH.Unfortunately the calvin cycle requires more ATP than NADPH so the chloroplast has to find a way to power photosystem II more often. This is where cyclic photophosphorylation comes into play. The sun still powers PSII to make ATP BUT... the energy from exciting PSI gets redirected back to PSII to make more ATP. This is cyclic instead of linear, hence, cyclic (cycle) photo (light) phosphorylation (adding phosphates onto the ADP). The Biology Place Take a look at the virtual chromatography lab included here. It outlines the process as well as how to calculate Rf, the reference front for pigments. A brief blurb about the Pearson company is included below. Virtual Chromatography Lab Chromatography Analysis Rf Value The Rf (Reference Front) value determines how far a pigment will travel depending on the solvent that it's submerged in. It's calculated as a decimal value by taking the distance the pigment traveled and dividing the distance the solvent traveled. This gives you a decimal percentage comparison value that's consistent for each pigment.Rf = Distance for pigment / distance for solvent. Calculate the Rf value. Please record your answer as 0._ Carotene 0.95 Xanthophyll 0.71 Chlorophyll a 0.65 Chlorophyll b 0.45 Accepted Rf Values Take a look at the value table below. Do the Rf experimental values you calculated from the virtual lab match to the accepted values? Pigments Accepted Rf Values Carotenoid 0.95 Xanthophyll 0.71 Chlorophyll a 0.65 Chlorophyll b 0.45 Pigments and Absorption frequencies Take a look at the absorption graph below. Remember that it shows which colors are absorbed easiest. Higher peaks means it absorbs that color, lower areas means it's not absorbing but reflecting. The graph shows three of the four pigments identified in lab. Locate the absorption information for xanthophyll and add it to the graph. This may be difficult to find, do your best and persevere. An approximation is fine. Use the graph above to answer the following questions. Which colors does chlorophyll b absorb best? blue and orange purple and blueish green purplyblue and orangish-red What color is this plant? Purple Blue Green Red Which light source color would be best for this particular plant? blue green red Photosynthesis Lab Part 2 In the second part of the lab we will be calculating the rate of photosynthesis for this plant under different light sources. Feel free to travel back to the virtual lab link from above to see a layout of the second part of the lab. Write a hypothesis using the structure "If (independent variable) then (dependent variable) because (reasoning)" Take a look at the image here and explain how we set up this lab by taking advantage of the form and function of a plant. Which of these would be a good control for the experiment and why? Lab Data Take a look at the images below and record your data in a spreadsheet. Time Disks Floating in Red Disks Floating in Orange Disks Floating in Yellow Disks Floating in Green Disks Floating in Blue Disks Floating in Purple 0 min 0 0 0 0 0 0 5 min 1 0 0 0 2 2 10 min 2 1 0 0 3 3 15 min 3 2 1 0 4 5 20 min 4 3 1 0 5 6 25 min 6 4 2 0 8 10 30 min 7 5 2 1 9 10 Graph your data here, don't forget a key. Calculate the Rate of Reaction for each color (Divide the amount of change in the DV / Amount of time )This will give you amount of leaves per minutes. Color Rate in Leaves Please record answer as 0._ Red 0.23 Orange 0.17 Yellow 0.07 Green 0.03 Blue 0.30 Purple 0.33 If you were farming this plant type what light sources would you spend your money on and why?