Photosynthesis (2.9)
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Notes:NOTES SL NOTES HLFor HL Extension See: 8.3REview:
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Thin Lined Chromatography (Practical #6)
Chromatography is the separation of pigments/ colors from a single source.
Calculation of Rf values allow scientists to determine what kinds of pigments are found in plants
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Light, Action Spectrum, and Plants
Light is an essential part of photosynthesis, you learn that from the time you are in elementary school. But what they don't tell you is why. Why is light so essential?
Why do plants have different photosynthetic pigments?
Why do plants have different photosynthetic pigments?
- Plants contain a variety of pigments within them that do various different things. Phytochromes (see 9.4), Chrolorphyll, Carotenoids, etc. Each have specific roles within the plant.
- Chlorophyll absorbs specific wavelengths of light.
- The absorbed energy from light is used to create chemical energy (ATP and NADPH) that is then used by the plant to produce sugar! Crazy.... more about that in the next section.
- Chlorophyll actually absorbs only specific wavelengths as do most pigments. Analyze the chlorophyll absorption spectrum. What do you notice?
- Each pigment absorbs specific wavelengths. While chlorophyll a really likes the ends of spectrum, chlorophyll b likes lighter blue hues, and carotenoids tend to prefer only the colors dark green through violet.
- When you add all of these together within a plant, you get what is called the action spectrum.
- Notice which colors are consistently ignored by chlorophyll and its counterparts? -Green and yellow to some degree.
So why are plants generally green?
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The Chloroplast
Chloroplast is one of 3 double membrane bound organelles.
Parts to draw attention to:
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Stages of Photosynthesis
Photosynthesis consists of two stages:
Together they convert: sunlight + water + carbon dioxide => sugar (glucose) + oxygen The energy needed to make the Calvin Cycle happen is produced in the Photosystems. (See side diagram) Equation: 6H20 + 6 CO2 --(Light)--> glucose (C6H12O6) + 6O2 Illuminating Photosynthesis (open in edge) |
Stage 1:
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Stage 2:
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Please see PHOTOSYNTHESIS (8.3) for more information
Limiting Factors of Photosynthesis
Three major factors that limit or influence how photosynthesis works.
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Changes in Earth's Atmosphere
Photosynthesis causes changes in the Earth’s atmosphere, oceans, and rock deposition.
Today the current theory is that the first photosynthesizing organisms evolved around 2.4 billion years ago (bya)
Today the current theory is that the first photosynthesizing organisms evolved around 2.4 billion years ago (bya)
- As a result of those organisms the CO2 decreased and O2 increased in earths atmosphere.
- Rocks absorb O2, where it combined with iron to create iron oxides
- ~1 bya rocks became saturated and O2 entered the atmosphere
- At 1% of current O2 levels, eurkaryotic metabolism is possible (~2 bya)
- Increased O2, metabolic pathways became more efficient and aerobic organisms increased
- O2 accumulated in the upper atmosphere is converted to ozone by sunlight, protecting the earth from UV light and creating a stable atmosphere (~400 mya)