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Biomolecules
Biomolecules are molecules produced by living organisms or are compounds that occur
naturally in plants and animals. They could be large macromolecules or smaller
molecules such as primary or secondary metabolites
Macromolecules
Proteins
Nucleic acids
Polysaccharides
Lipids
Small Molecules
Terpenoids
Steroids
S
Sugar
D
Derivatives
i i
Amino Acids and Peptides
Alkaloids
Nucleic Acids
Nucleic
N
l i acids
id (DNA andd RNA) are unquestionably
ti bl the
th top
t level
l l molecules
l l because
b
they store our genetic information. They are polymers of nucleotides, which themselves
are made of three parts—a heterocyclic base, a sugar, and a phosphate ester.
N l tid
Nucleotide
The base alongg with the sugar
g forms
a nucleoside, which combined with
the phosphate group forms the
nucleotide
Phosphates are key compounds in nature because they form useful stable linkages
between molecules and can also be built up into reactive molecules by simply
multiplying
lti l i the
th number
b off phosphate
h h t residues.
id
Th mostt important
The
i
t t off these
th
nucleotides
l tid
is also one of the most important molecules in nature—Adenosine triphosphate or ATP.
The Components of Nucleic Acids
IIn nucleic
l i acids
id there
th
are only
l five
fi bases,
b
t
two
sugars, andd one phosphate
h h t group
possible. The bases are monocyclic pyrimidines or bicyclic purines and are all
aromatic. The two sugars are ribose (RNA) and 2-deoxy ribose (DNA).
Bases
Sugar
NH2
N
O
O
N
N
N
H
N
H
N
HO
NH
HO
NH2
N
O
NH2
O
HN
N
HN
OH
ribose
ib
(RNA)
guanine
adenine
OH
O
HO
HO
O
N
H
uracil
(RNA)
O
N
H
thymine
(DNA)
O
N
H
cytosine
2-deoxyribose
(DNA)
OH
The Double Helix Structure
Each polymeric strand of DNA coils up into a helix and is bonded to another strand by
hydrogen bonds between the bases.
bases Each base pairs up specifically with another base:
adenine with thymine (A–T) and guanine with cytosine (G–C)
NH2
OH
O
N
N
P
HO
O
N
A N
O
N
N
5'
O
N
O
A
HO
N
adenine
N
Double Helix
H
HN
P
O
thymine
H
O
2'
O
N
N
3'
O
N
R
N
P
HO
NR
N
H
NH2
O
H
H
N
O
O
N
O
NR
cytosine
O
O
O
N
O
N
T
N
R
HO
H
N
H
N
guanine
N
H
Each purine (A or G) is bonded specifically to one pyrimidine (T or C) by two or by
three hydrogen bonds. The hydrogen bonds are of two kinds: one links an amine to a
carbonyl group and one links an amine to an imine.
Modified Nucleosides and Bases
Proteins
Proteins
P
t i are made
d off amino
i acids
id andd are formed
f
d in
i living
li i organisms
i
b d on the
based
th
information contained in DNA.
-TACDNA Triplet
RNA Synthesis
-AUGRNA Triplet
Instruction to begin
Protein Synthesis
Polyamides
Protein Synthesis
H
NH2
HOOC
Methionine
S
Structure of Proteins
A i acids
Amino
id are the
th basic
b i units
it off proteins
t i andd are linked
li k d together
t th through
th
h amide
id bonds.
b d
R
OH
H2N
O
L-amino acid
The R-groups can be alkyl, aromatic, alcoholic or phenolic, thiol or thioether, basic
groups like amine or guanidine and carboxylic acids. In proteins these individual
groups act together to perform various functions.
functions
The linear chain of amino acids (primary structure), folds itself through various
interactions to give secondary,
secondary and tertiary structures.
structures In some proteins,
proteins two or more
tertiary structured protein subunits join together to give quaternary structures. The
function of a protein is highly affected by the three dimensional structure it can adopt.
The function of certain proteins is to provide structural stability.
Glutathione – A functional tripeptide
S ll chains
Smaller
h i off amino
i acids,
id joined
j i d together
t th by
b amide
id bonds
b d are called
ll d peptides.
tid
NH2
O
H
N
HOOC
N
H
COOH
O
SH
glutathione - RSH
Glutathione is a tripeptide formed from glutamic acid,
acid cysteine and glycine.
glycine The middle
amino acid is the vital one for the function—cysteine with a free SH group.
Thiols are easily oxidized to disulfides and glutathione sacrifices itself if it meets an
oxidizing agent.
agent Later,
Later the oxidized form of glutathione is reduced back to the thiol.
thiol
OH
H2O
OH
HO
S
R
SH
R
H
OH
H2O
OH
S
R
R
RS
SR
HS
Glutathione
Gl
t thi
also
l actt as a nucleophile
l hil andd reactt with
ith toxic
t i compounds
d that
th t enter
t the
th
body to make them harmless substances
Lipids
Lipids (fats) are important components of cell membranes.
membranes They are essential to the
function of membranes as selective barriers to the movement of molecules.
The most common types of lipids are esters of glycerol. Glycerol is just propane-1,2,3triol
i l but
b it
i has
h interesting
i
i stereochemistry.
h i
It is
i not chiral
hi l as it
i has
h a plane
l
off symmetry,
but the two primary OH groups are enantiotopic. If one of them is changed—by
esterification, for example—the molecule becomes chiral. Natural glycerol phosphate is
such an es
suc
ester
e andd it iss op
optically
c y active.
c ve.
Typical lipids found in food are triesters of glycerol
with various fatty acids, depending on the source.
For example: Olive oil is the triester of glycerol with
oleic acid – a 18 carbon carboxylic acid with a cisdouble bond between the 9th and 10th carbon atoms.
O
O
O
R
O
O
O
R
R
Sugars
Sugars are the building blocks of carbohydrates. Their functions include,
Provision of energy
Construction of cell wall
Recognition of proteins
Sugars normally exist in cyclic forms.
Glyceraldehyde is the simplest aldehyde sugar or aldose and dihydroxyacetone is the
simplest keto-sugar or ketose.
CHO
O
HO
OH
glyceraldehyde
HO
OH
dihydroxyacetone
Glycosides