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Photosynthesis Auto- & Hetero trophs Review Autotrophs, through the process of photosynthesis convert sunlight into energy, consume CO2 in that process and release O2.(photosynthetic plants and chemosynthetic organisms) “producers” Heterotrophs cannot do any of that, but must obtain their energy by being consumers instead of producers Chemical Energy and ATP ATP (adenosine triphosphate) is the compound used by cells to store energy ADP (adenosine diphosphate) will become ATP by adding another phosphate group, thus ADP is like a partially charged battery, ATP is like a fully charged battery More on ATP When the high energy bond between the phosphates is broken, energy is released. (ATP is converted to ADP) Web site that explains the ADP/ATP concept. http://www.brooklyn.cuny.edu/bc/ahp/LAD/C7/C 7_atp.html Cells use ATP for: active transport,intracellular movement, and production of heat More on ATP ATP in cells is in short supply and is used up quickly Glucose contains about 90 times the energy of an equal amount of ATP Cells generate ATP from ADP when necessary by using the energy in carbohydrates Van Helmont’s experiment 1600’s Van Helmont found that the mass of a plant increased over time, but the mass of the soil it grew in did not change. Where did the increase in mass come from? Addition of water accounted for most of mass gained by plant over time The carbon part of the increase in carbohydrate mass had to come from the atmosphere. Conclusion: something is going on with the stuff in the air (CO2) and sunlight Priestley’s Experiment Experiment with flame in a jar showing that O2 is consumed by the flame Placed a plant in the jar which replenished the O2, thus showing that the plant was producing O2 Secondary conclusion: light necessary for O2 production Ingenhousz Experiment Built on Priestley’s work, but showed that the effect of the plant was impacted by the plant being exposed to light. Secondary conclusion: plant being exposed to CO2 and light allowed for O2 production Ingenhousz NOT pictured here--- Photosynthesis Equation Photosynthesis Equation Light and Pigments “light” is composed of many different colors of light (due to different wavelengths) “white” light is composed of these different wavelengths being together. Plants gather the light energy with pigments such as chlorophyll a & chlorophyll b Chlorophyll does NOT absorb the green wavelengths of light, that is why we see chlorophyll appears green Carotene is another pigment (does not absorb the red and orange wavelengths) Each color has a different wavelength Red is next to infrared UV is next to violet Wavelength is related to energy Inside a Chloroplast Thylakoids are saclike photosynthetic membranes that contain clusters of chlorophyll and other pigments that can capture the energy of sunlight Photosynthesis has a light-dependent stage which occurs within the thylakoid membrane The light-independent stage (AKA: the Calvin Cycle) Occurs in the stroma, which is a region outside the thylakoid membrane NADP+ and NADPH NADP+ has the job of moving the energy captured by photosynthesis to other places in the cell so that it can be used NADP+ adds 2 high energy electrons and an H+ ion, then is changed into NADPH, which can be used by the cell for building other molecules, such as carbohydrates (glucose) NADP+ is nicotinamide adenine dinucleotide phosphate Light-Dependent Reactions Light-dependent reactions convert ADP and NADP+ into ATP and NADPH and produce Oxygen in the process The Calvin Cycle During the Calvin Cycle, plants use the energy that ATP and NADPH contain to build high energy compounds that can be stored for a longer time. The Calvin Cycle uses the ATP and NADPH from light-dependent reactions to produce high energy sugars The Calvin Cycle does not require light to occur, thus is considered light-independent. The Calvin Cycle (Light Independent Reaction) Carbon Fixation Calvin Cycle Details 6 CO2 molecules enter the cycle from the atmosphere, The CO2 combines with six 5-Carbon molecules, resulting in twelve 3-carbon molecules Using the energy of ATP and NADPH, the Twelve 3 –carbon molecules are converted into higher energy forms Two of the Twelve 3-carbon molecules are converted into two similar 3-carbon molecules. These 3-carbon molecules are used to form various 6-carbon sugars and other compounds The remaining ten 3-carbon molecules are converted back into six 5-carbon molecules. These combine with the six new CO2 molecules to begin the next cycle. Factors that Affect Photosynthesis Inadequate water will slow or stop photosynthesis Temperatures outside of the optimal range (0C- 35 C) may destroy enzymes, slowing or stopping photosynthesis Light intensity will have a direct impact on the rate of photosynthesis. (Low intensity=less photosynthesis, High intensity=more photosynthesis)