Experiment 1 - pigments

Question 1

what is a colorant

Answer 1

a generic term that describes any substance that colors something

Question 2

pigments

Answer 2

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

Question 3

classification of pigments

Answer 3

solubility and chemical structure

Question 4

what are the classifications of pigments acc to structure

Answer 4

isoprenoid derivatives
tetrapyrrole derivatives
benzopyran derivatives
betalamic acid derivatives

Question 5

chlorophyll

Answer 5

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

Question 6

main components of chlorophyll

Answer 6

phytol tail
porphyrin ring

Question 7

what is the ion present in the porphyrin ring?

Answer 7

magnesium

Question 8

what is the R group in chlorophyll a?

Answer 8

Ch3 or methyl group

Question 9

what is the R group in chlorophyll b?

Answer 9

CHO or carbohydrates

Question 10

what is the hydrophobic part of a chlorophyll molecule

Answer 10

phytol tail

Question 11

what is a porphyrin ring

Answer 11

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

Question 12

what is the nucleus of all chlorophylls?

Answer 12

phorbin

Question 13

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

Answer 13

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

Question 14

exposure of chlorophyll to severe heat or acid generates what pigments

Answer 14

pheophytin
pyropheophytin

Question 15

the formation of chlorophyllides results from what activity

Answer 15

chlorophyllase activity

Question 16

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

Answer 16

true

Question 17

at what pH is chlorophyll more heat stable?

Answer 17

in basic pH or around pH 9

Question 18

at what pH is chlorophyll unstable?

Answer 18

around pH 3

Question 19

pyrochlorophylls are formed when

Answer 19

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

Question 20

formed from the enzymatic cleavage of phytol from pheophytin

Answer 20

pheophorbides

Question 21

true or false:
chlorophylls are susceptible to photodegradation

Answer 21

true

Question 22

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

Answer 22

true

Question 23

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

Answer 23

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

Question 24

what are carotenoids

Answer 24

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

Question 25

classes of carotenoids

Answer 25

hydrocarbon carotenes oxygenated xanthophylls

Question 26

carotenoids are formed with what polymerization?

Answer 26

head-to-tail polymerization of isoprene units

Question 27

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

Answer 27

at least 9

Question 28

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

Answer 28

color gets darker or wavelength shifts to a redder color

Question 29

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

Answer 29

trans: deeper color cis: color fading

Question 30

are all carotenoids precursors of vitamin a?

Answer 30

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

Question 31

carotenoids are easily oxidized because?

Answer 31

of their large number of conjugated double bonds

Question 32

oxidatibe destruction of beta carotene is intensified in the presence of

Answer 32

sulfite and metal ions

Question 33

what enzyme hastens oxidative degradation of carotenoid pigments

Answer 33

lipoxygenase

Question 34

are carotenoids moderately heat stable

Answer 34

yes

Question 35

what process destroys enzymes that bleach carotenoids

Answer 35

blanching

Question 36

Carotenoids are more stable in what pH?

Answer 36

basic

Question 37

anthocyanin colors

Answer 37

blue, pink, or violet

Question 38

term used to describe anthocyanin because of its pH dependency

Answer 38

amphoteric molecule

Question 39

building block of anthocyanin

Answer 39

flavylium cation

Question 40

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

Answer 40

true

Question 41

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

Answer 41

true

Question 42

this can either accelerate or retard degradation in anthocyanin

Answer 42

copigmentation

Question 43

color of anthocyanin in acidic environment pH 2

Answer 43

red

Question 44

at which pH condition is anthocyanin more stable

Answer 44

acidic pH

Question 45

heating anthocyanjn shifts the equilibria to toward what form?

Answer 45

chalcone form/yellow/colorless

Question 46

formation of unstable anthocyanidins happen because of

Answer 46

anthocyanin hydrolysis which is favored by heat

Question 47

are anthocyanins susceptible to oxidation?

Answer 47

yes because of their unsaturated nature

Question 48

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

Answer 48

0.63 to 0.79