Anthocyanins are water-soluble due to sugar residues that allow hydrogen bonding with water molecules. Carotenoids are fat-soluble due to their large hydrophobic polyene backbones. Heme and chlorophyll contain porphyrin rings that absorb light at specific wavelengths, appearing red and blue-green respectively. Their conjugated double bond structures allow electron excitation and energy level changes when certain wavelengths of light are absorbed.

1. By: IZZATI, RAUDAH, WAN ALIA.

2. 10.1 COMPARE THE SIMILARITIES AND
DIFFERENCES IN THE STRUCTURE OF THE
NATURAL PIGMENTS:
ANTHOCYANINS, CAROTENOIDS, CHLOROP
HYLL AND HEME

3. Anthocyanins.

4. Carotenoids.

5. Chlorophyll.

6. Heme.

7. SIMILARITIES
• BETWEEN HEME AND CHLOROPHYLL
- Contain a planar heterocyclic unit called a
porphin whose structure contain a cyclic
system of conjugated double bonds.
- Porphins with substituents in positions 1 to 8
are called porphyrins.

8. Resonance structure of porphine
Conjugate double bonds is possible by means of alternating single and
double bond.

9. DIFFERENCES
ANTHOCYANIN CAROTENOID CHLOROPHYLL HEME
1. Has a C6C3C6 1. Derived from a 1. 2 types of 1. Hemoglobin
skeleton with 2 40-carbon polyene chlorophyll: contains 4 heme
conjugated benzene chain. -chlorophyll a: blue- subunits while
rings isolated by an green myoglobin contains
oxygen-containing -chlorophyll b : one heme ring
pyran ring. yellow-green
2. Always have a 2. May be 2. Chlorophyll b 2. A haemoglobin
sugar residue at terminated by cyclic differs from molecule contains 4
position 3 and end-groups and chlorophyll a by protein chains
glucose occur at may be having an aldehyde while myoglobin
position 5,7,3’ and complemented (-CHO) group in molecule contains
4’. with oxygen placed of a methyl one protein chain
containing group
functional groups. (-CH3).

10. 3. It is porphyrin 3. Each heme ring
pigments, contains one iron
composed of 4 ( II) ion
pyrrole ring to form
tetrapyrrole with
magnesium ion
complex in the
centre of the ring.
4. The iron in the
heme group is
coordinated to the
four nitrogen atoms
in the prophyrin
ring and also to a
nitrogen atom from
the histidine
residue of the
hemoglobin protein
known as the globin

11. 5. The 6 position
around the iron of
the heme is
occupied by oxygen
when the
haemoglobin
protein is
oxygenated

12. 10.2 EXPLAIN WHY
ANTHOCYANINS, CAROTENOIDS, CHLOROP
HYLL AND HEME GROUP FORM
COLOURED COMPOUND WHILE MANY
OTHERS ORGANIC MOLECULES ARE
COLOURLESS.

13. a) Chromophores are unsaturated groups of atoms in
organic compounds whose electron absorb
radiation in the visible and ultraviolet region of the
electromagnectic spectrum.
b) The wavelength of light absorb by different
chromophores are characteristic of the
chromophores and can be used for their
identification.
c) They can change with temperature, solvent, extend
of conjugation and the presence of saturated
groups.

14. d) Anthocyanins
• The absorbance spectrum is similar with
cyanidin.
• Cyanidin is the parent compound of the
anthocyanins but lacks of glucose residue.
• Under acidic conditions (low pH) cynidin is
red.

15. • Graph
• The absorbance at 375 nm lies in the UV region of the electromagnetic
spectrum so it has no effect on the observed colour f cyaniding
• But, the absorbance at the 530 nm lies in the blue-green region of the
visible spectrum hence cyaniding transmits the complementary colour
of the eye, namely red.
• Although the absorbance spectra of anthocyanins will be similar with
cyanidin but it will vary with due to the presence of differential
functional group.
• The colours of anthocyanins will also vary with temperature and pH
due to the presence of forms in equilibrium.

16. e) In Carotenoids and Chlorophyll
• Different molecule absorb light at different wavelength
because of differences in their electronic structures.
• Figure 2 shows the absorption spectra of the two closely
related chlorophylls (a and b) and carotenoid found in plant.

17. • It is the electronic arrangement of a molecule that is responsible for
the absorption of light in the ultraviolet and visible region of the
electromagnetic spectrum.
• It is the electron in the molecule that are largely responsible for
the absorption of light in the visible.
• A bond consist of two electron in a spin pair arrangement-one
electron spins clockwise and the other spins anticlockwise.
• The total potential energy increases as a result of absorption of
light.
• The absorption of light by electron in a bond can be viewed in
terms of an energy level diagram. (Figure 3)
*
hf (photon)
Figure 3

18. • The diagram shows the light wave (photons) as a
squiggly arrow.
• One of the electron and has absorbed this
energy and moved from the ground state( ) to an
excited state ( *).
• Now the two electrons will no longer have
complementary spins.
• This energy jumped occurs only when light of
exactly the right wavelength (energy) is absorbed.
• The reflected light will have a different energy
from the incident light and will have a different
colour.

19. f) Heme
• As the heme group is in red colour so the
intensity of absorption of electron is high at
the blue-green region of visible
electromagnetic. spectrum.
• Therefore the reflected light is red in colour.

20. 10.3 DEDUCE WHETHER ANTHOCYANINSAND
CAROTENOIDS ARE WATER SOLUBLE OR
FAT SOLUBLE FROM THEIR STRUCTURE.

21. Natural pigment Explaination
-freely soluble in water but
poorly soluble in non-polar
organic solvents
-presence of 1 or more residues
helps the anthocyanins
maintains its solubility in water.
Anthocyanins -the sugar residue contain 1 or
more OH- group which can
hydrogen bond with water
molecules.
-if sugar is hydrolyse, the
solubility decreases.

22. Natural pigment Explaination
-poorly soluble in water but freely
soluble in non-polar organic solvent
because it is essentially hydrocarbon
in nature of the solvent.
-the polar functional groups
outweighed by the much larger
polyene backbone, which is
Carotenoids hydrophobic.
-dissolving carotenoid in water would
be an energetically unfavoured
process as hydrogen bond between
water molecules would be replaced
by VDW
-carotenoids that are soluble in water
contains carboxylic functional group.

23. THANK YOU 