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Lab > Experiment 1 - pigments > Flashcards

Experiment 1 - pigments Flashcards

1
Q

what is a colorant

A

a generic term that describes any substance that colors something

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2
Q

pigments

A

natural constituents of cells and tissues of plants or animals that imparts color

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3
Q

classification of pigments

A

solubility and chemical structure

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4
Q

what are the classifications of pigments acc to structure

A

isoprenoid derivatives
tetrapyrrole derivatives
benzopyran derivatives
betalamic acid derivatives

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5
Q

chlorophyll

A

green pigment in plants tissues that allow plants to absorb light energy through photosynthesis

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6
Q

main components of chlorophyll

A

phytol tail
porphyrin ring

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7
Q

what is the ion present in the porphyrin ring?

A

magnesium

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8
Q

what is the R group in chlorophyll a?

A

Ch3 or methyl group

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9
Q

what is the R group in chlorophyll b?

A

CHO or carbohydrates

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10
Q

what is the hydrophobic part of a chlorophyll molecule

A

phytol tail

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11
Q

what is a porphyrin ring

A

a fully unsaturated macrocyclic structure containing four pyrrole rings linked through methine bridges

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12
Q

what is the nucleus of all chlorophylls?

A

phorbin

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13
Q

what are the derivatives formed and thejr color when chlorophyll is exposed to heat and acid?

A

Mg-free: olive brown, Mg-containing: green

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14
Q

exposure of chlorophyll to severe heat or acid generates what pigments

A

pheophytin
pyropheophytin

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15
Q

the formation of chlorophyllides results from what activity

A

chlorophyllase activity

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16
Q

true or false: chlorophyllides are less heat stable and more likely to degrade to Mg-free derivatives liek pheophorbide

A

true

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17
Q

at what pH is chlorophyll more heat stable?

A

in basic pH or around pH 9

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18
Q

at what pH is chlorophyll unstable?

A

around pH 3

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19
Q

pyrochlorophylls are formed when

A

chlorophylls lose the C-10 carbomethoxy group prior to displacement of the magnesium from the porphyrin ring

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20
Q

formed from the enzymatic cleavage of phytol from pheophytin

A

pheophorbides

21
Q

true or false:
chlorophylls are susceptible to photodegradation

A

true

22
Q

tdue or false: complete color loss/bleaching happens when chlorophyll is exposed to light and oxygen

A

true

23
Q

reaction which leads to destruction of porphyrins (total loss of color)

A

hydroxy radicals/singlet oxygen reacts with tetrapyrroles forming peroxide free radicals leading to distruction of porphyrins

24
Q

what are carotenoids

A

are fat-soluble compounds having yellow, orange, or red shades

25
Q

classes of carotenoids

A

hydrocarbon carotenes
oxygenated xanthophylls

26
Q

carotenoids are formed with what polymerization?

A

head-to-tail polymerization of isoprene units

27
Q

carotenoids require at leasr how mang conjugated double bonds before the appearance of yello color?

A

at least 9

28
Q

as the number of conjugate bonds in caretoneoids increases, what happens to the color?

A

color gets darker or wavelength shifts to a redder color

29
Q

trans bond in carotenoids:
cis bonds in carotenoids:
what color

A

trans: deeper color
cis: color fading

30
Q

are all carotenoids precursors of vitamin a?

A

no
vit a precursor have the presence of unsubstituted beta ionine ring

31
Q

carotenoids are easily oxidized because?

A

of their large number of conjugated double bonds

32
Q

oxidatibe destruction of beta carotene is intensified in the presence of

A

sulfite and metal ions

33
Q

what enzyme hastens oxidative degradation of carotenoid pigments

A

lipoxygenase

34
Q

are carotenoids moderately heat stable

A

yes

35
Q

what process destroys enzymes that bleach carotenoids

A

blanching

36
Q

Carotenoids are more stable in what pH?

A

basic

37
Q

anthocyanin colors

A

blue, pink, or violet

38
Q

term used to describe anthocyanin because of its pH dependency

A

amphoteric molecule

39
Q

building block of anthocyanin

A

flavylium cation

40
Q

true or false: more OH groups in anthocyanin decreases its stability

A

true

41
Q

true or false: higher -Ome substituents in anthocyanin increases its stability

A

true

42
Q

this can either accelerate or retard degradation in anthocyanin

A

copigmentation

43
Q

color of anthocyanin in acidic environment pH 2

A

red

44
Q

at which pH condition is anthocyanin more stable

A

acidic pH

45
Q

heating anthocyanjn shifts the equilibria to toward what form?

A

chalcone form/yellow/colorless

46
Q

formation of unstable anthocyanidins happen because of

A

anthocyanin hydrolysis which is favored by heat

47
Q

are anthocyanins susceptible to oxidation?

A

yes because of their unsaturated nature

48
Q

stability of anthocyanin is good at what range of water activity range

A

0.63 to 0.79

Lab (3 decks)

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