Ch 6 – Photosynthesis process that converts light energy into chemical energy supports most life...
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Transcript of Ch 6 – Photosynthesis process that converts light energy into chemical energy supports most life...
![Page 1: Ch 6 – Photosynthesis process that converts light energy into chemical energy supports most life on Earth found in algae, plants, some bacteria & protista.](https://reader035.fdocuments.in/reader035/viewer/2022072013/56649e5f5503460f94b593f6/html5/thumbnails/1.jpg)
Ch 6 – Photosynthesis
• process that converts light energy into chemical energy
• supports most life on Earth
• found in algae, plants, some bacteria & protista
• the summarized equation
6CO2 + 6H2O C6H12O6 + 6O2
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Photosynthesis occurs inside the chloroplast on the membrane of the thylakoids and in the stroma.
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Of the electromagnetic spectrum, photosynthesis only uses the visible spectrum (wavelengths we can see).
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The most common colors that are absorbed by the pigments are reds and blues. The other colors are reflected thus making chloroplast green.
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Photosynthesis is divided into 2 stages.
1. Light Reactions
• occurs only with light
• utilizes protons (H+), electrons (e-) & H2O to make cellular energy
2. Calvin Cycle
• occurs in light and dark
• utilizes CO2 & cellular energy to make organic compounds
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The Light Reactions
• Light energy entering the chlorophyll pigments (embedded in Photosystem II) raise the available electrons (e-) to a higher energy level.
• These electrons are passed through special molecules in the membrane creating an Electron Transport Chain.
• This in turn moves protons (H+) into the thylakoid as the electrons lose their higher energy level.
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• Next the electrons are passed to Photosystem I (more chlorophyll pigments) and the electrons are again raised to a higher energy level.
• Again the electrons are passed through an Electron Transport Chain this time bonding with NADP+ & a proton forming NADPH (a type of cellular energy).
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• Since the electrons are lost at the end of second transport chain, new electrons must be found.
• Photolysis splits 2H2O molecules into O2, protons (4H+) and electrons (4e-).
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• The last step is to use the concentration gradient of protons (H+) that has been created by the first electron transport chain & photolysis.
• Chemiosmosis uses the protons (H+) leaving the thylakoid as energy in ATP synthase (special protein) to attach a phosphate to ADP forming ATP.
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ATP (adenosine triphoshate)
• Cellular energy
• ATP releases energy by breaking a bond as the 3rd phosphate group is removed.
NADP+
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The Calvin Cycle
• Not driven by light, occurs day or night.
• CO2 enters the Calvin cycle and bonds (fixed) to a 5 carbon molecule RuBP. [carbon fixation]
• This new molecule is unstable and splits into two 3 carbon molecules 3-PGA.
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• The 3-PGA are modified by the ATP & NADPH produced in the light-dependent reactions into G3P.
• One of the G3P leaves the cycle to form organic compounds (carbohydrates).
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• The remaining G3P’s are converted back to RuBP by ATP thus starting the cycle again.