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Plant pigments & secondary metabolites

Plant pigments & secondary metabolites - BICD 120...

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Unformatted text preview: BICD 120, Fundamentals of Plant Biology CrawfordlSchmidt OH 0+ 1 HO O \ O OH HO O O\ O OH HO / OH / OH OH OH PELARGONIDIN 19—37. Three anthocyanin pigments, the basic pigments on which flower colors in many angiosperms depend; pelargonidin (red), cyanidin (violet), and delphinidin (blue). Related compounds known as flavonols are yellow or ivory, and the carotenoids are red, orange, or yellow. Betacyanins (betalains) are red pigments that occur in one group of dicots. Mixtures of these different pigments, together with changes in cellular pH, produce the entire range of flower color in the angiosperms. Changes in flower color provide "signals" to pollinators, telling them which flowers have opened recently and are more likely to provide CYANIDIN H1C=CH H3C Hac DE LPHINIDJN CHQCHJ food. O=(l: fi—O_CH3 J ? 0 CH2 7-6. Chlorophyll a is a large molecule with a central cIH core consisting of a magnesium ion held in a porphyrin n ring. Attached to the ring is a long, insoluble carbon- ?‘CH; hydrogen chain, which serves to anchor the molecule to CH2 specific, hydrophobic proteins of the internal [ membranes of the chloroplast. Chlorophyll b differs ICHz from chlorophyll a in having a —CHO group in place of CH: the —CH3 group indicated in color. Alternating single éH and double bonds (known as conjugated bonds), such as _CHJ those in the porphyrin ring of chlorophylls, are (EH2 common among pigments (see also Figure 7-8). Note I the similarity between the chlorophyll a molecule shown EH1 here and the cytochrome molecule of Figure 6-9. CH2 I CH_CH'\ I _ i“? i”: i”“ CH3 CH, CH3 ffls CH3 J, CH3 I $143 CH3 CH3 CH =CH—C=CH—-CH =CH--C=CH —CH éCH— CH=C—CH=CH-—CH=C—CH=CH CH3 CH3 CH3 CH3 CH3 BEFA-CAROTENE CH=CH—C=CH—CH=CH—C=CH—CH:OH CH3 VITAMIN A (RETINOL) CH3 CH3 H3C CHE; CH3 CH3 CH3 i l CH=CH—C=CH—CH=CH—C=CH‘-C—-H I! O CH; RETJNAL CH3 CH3 CH=CH—CI=1CH'- CH =CH—?=CH—CH=CH—CH:(IZ—CH=CH —CH=C—-CH=CH | CH3 CH3 CH3 CH3 CH3 H3C OH ZEAXAN'THIN 7-8. Related carotenoids. Cleavage of the beta-carotene molecule at the point indicated by the arrow yields two molecules of vitamin A (retinol). Oxidation of vitamin A yields retinal, the pigment involved in vision. Note the conjugated bonds (alternating single and double bonds) in the carbon chains. anxanthin (a xanthophyll) is the pigment responsible for the yellow color of corn (Zea mays) kernels. HC QOH HC ll ll H OH OCH H OH OCH l/ ° i/ ° HOC Hoc l | ‘ H H coniferyl alcohol a OCH, sinapyl alcohol “EQC’” ‘- -H OH I/ 00 | H p-coumaryl alcohol H Figure 15-13 (a) Common phenolic subunits found in lignins. (b) Modei of partial structure of lignin. rich in coniferyi alcohol. During lignin formation. a variety of different interlocking bonds are formed by free-radical mechanisms. and bond formation depends partly on where in thejoining molecules the free radicals are when collision occurs. Also. oxidation at the double bond of the three-carbon alcohol side chain in building blocks (a. above) causes several possible covalent bonds to form. Clearly. no lignin can be identical to another, even though all are similar. CHon CH,OH | | Hc—o cho l I HCOH HCH OH HC=O $H=OH O 00H, CHO Hr!) CHao Hf‘o_ 3 0 ll O—CH H H . CH (I: =0 | ‘ CH 1 HCOH CH,0 _ chH CHao OH /0\ 0—CH- l HOCH H“? <le = OCH HCOH HE: G a HC—CH l OCH= HC|> (le HCOH CHZOH \ / ’ CHEOH H O | HOHzC—C=C CH o——-CH H l HCOH - CH,O OCH, HC—wO 00H, 0 HOCHZ HOHz? CH30 HC HCIZ OCH, 1 HC--‘-O HCOH CHaOH H COH ergo OCH: I 2| CH,o OCH, 0 CH HC 0 | ' I HCO c=o CH,o I I 00H, b 0H 0 Frau]: Plant Bide/i)" emu... ém/Lm—f—ngox 334501., Alkaloids o o / N T/ ii /CH3 I i CH HC C \ CH 3 \N/ \C N\ N 3 CH é (I; //C—“H nicotine ;\ oé \N/ “‘N 0 CH3 CH— coocm Gamma N—CH, CH— 0— COQHO CH1 (i? /CHCOC3IF1€ HxN/Cx C/N\ Hjco C—H J: L // 0H 0% i/ N H N . quinine CH3 NHCHJ _ theobromine . . (a) ephedrine codeine FIGURE 3.27 Alkaloids (a) Structures of‘several alkaioids, which have notable effects on the human body‘ (b) Cultivated tobacco (Nicotiana), after which the alkaloid nicotine is named. Terpenes isoprene (subunit) H3C/ \‘CHI limonene (monoterpene) heavea rubber (COmplex terpene) ...
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