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THE CHEMISTRY OF AUTUMN COLORS. Martin Drastík. Why would I like to speak about this topic? Sad but beautiful. Pigments. C hlorophyll – green C arotene – orange A nthocyanin – red, purple. C hlorophyll. Molecule is large (C 55 H 70 MgN 4 O 6 ) Porphyrin ring + magnesium - PowerPoint PPT Presentation
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THE CHEMISTRY OF AUTUMN COLORS
Martin Drastík
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Why would I like to speak about this topic? Sad but beautiful
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Pigments
Chlorophyll – green Carotene – orange Anthocyanin – red, purple
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Chlorophyll Molecule is large
(C55H70MgN4O6)
Porphyrin ring + magnesium
Situated in leafs – organelles
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Chlorophyll Chloroplasts Not soluble in
the aqueous solution of cells
Photosynthesis of sugars and starches
tescarbohydraOOHCO 2lchlorophyllight
22
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Chlorophyll Why do the leaves seem to be green? Absorption spectrum
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Chlorophyll
Not a very stable
compound;
decomposed
by bright sunlight
Continuously synthesized in leaves (requires sunlight and temperatures) until autumn
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Carotene Large molecule (C40H36)
Situated in the chloroplasts Function: accessory absorber - energy transferred to chlorophyll
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5
1
4
2
3
7
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CH318
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10
11
12
13
14
15
15'
14'
13'
CH320'
12'
11'
10'
9'
CH319'
8'
7'
CH317
CH316
CH319
CH320
1'
6' 2'
3'5'
4'CH318'
CH316'
CH317'
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Carotene Absorption spectrum Much more stable than chlorophyll Carotene persists in leafs even when chlorophyll has disappeared
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Anthocyanin Various structures –
diff. is „B“ benzenoid ring
Disolved in the aqueous solu-
tion of cells
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Anthocyanin Absorption spectrum
Color is sensitive to the pH of the cell sap
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Anthocyanin If the sap is acidic – bright red If the sap is neutral – purple If the sap is alkaline – orange
alkaline; neutral; acidic
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Anthocyanin Formed by a reaction between sugars and
certain proteins in cell. Occurs when concentration of sugar in the sap is high enough.
Requires light Red side insolate
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Conclusion Summer:
Autumn: stop of producing chlorophyll, storing energy in fruit
and nuts
changing color of leaves
tescarbohydraOOHCO 2lchlorophyllight
22
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Thank you for your attention
The biggest source of information:
Prof. Shakhashiri, University of Wisconsin-Madison Chemistry: Chemical of the Week
Pictures – internet
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