Introduction
Lipids, Proteins, and Carbohydrates
Biochemistry
 Biochem is the study of biological materials


Compounds of biological origin
Chemistry of biological processes
 Biological materials are primarily made up of:


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Lipids
Proteins
Carbohydrates
Lipids
 Fat-like compounds that leave grease mark
 Insoluble in water but soluble in organic
solvents
 Fats are esters, reacting alcohol & organic
acid produces ester
 Alcohol in fats is always glycerol,
 The organic acid obtained from fats is called
fatty acid
Fatty Acids
 Mono-carboxylic acids, -COOH
 Contain even number of H
 Have long & straight Carbon chain (20)
 Have 4 or less double bonds
R1-COO-R1’
l
R2-COO-R2’ A generic formula for a triglyceride
l
R3-COO-R3’
Oils
 Veg oils are liquid at room temp. (low melt point)
 VOs are less saturated than animal fats
 Less saturated oils has greater number of C=C
 Hydrogenation is adding H to C=C bonds to
make the oil saturated (solid)
 Degree of unsaturation is normally measured by
the Iodine number. It is grams of Iodine that is
decolorized by 100 grams of fat.
Hydrolyzing Fats
 Hydrolyzing fats with inorganic bases is called
saponification (yields glycerol & soap)
 Sodium hydroxide makes hard soap and
potassium hydroxide or ammonium hydroxide
make soft soap.
 Fats become rancid when exposed to moist air,
microorganisms act as catalysts to hyrolyze the
fat
 Oxygen and ozone in the air oxidize the C=C
bonds, producing aldehydes, acids, and
peroxides that are the cause of rancid odor.
Waxes
 Waxes that cover the fur and feather, and top
of the shiny plant-leaf and beeswax are
compound lipids that are also esters.
 Waxes like paraffin are pure hydrocarbons and
NOT fats or esters.
Proteins
Introduction
 Proteins make up our muscles, skin, and the
biological catalysts called enzymes
 Proteins do not accumulate in the body.
 Excess proteins breaks down in the body and
get excreted in the
H2N-C-NH2
form of urea:
ll
O
 We can manufacture protein through various
bacteria
Protein Structure
 Proteins are polymers
 They are formed like strings of beads
 Small units of protein chains is called amino
acids
 About 20 amino acids make up all known
proteins
 The amino acids have both amine group and
the acid group attached to the same carbon
atom (alpha amino acids)
Alpha amino acid structure
Chemical Structure of a common amino acid:
H
l
H2N-C-COOH
ll
R1
R1 is the organic “tail” of the amino acid
List of Amino Acids
AMINO
ACID
THREE LETTER
CODE
SINGLE LETTER
CODE
glycine
Gly
G
alanine
Ala
A
valine
Val
V
leucine
Leu
L
isoleucine
Ile
I
methionine
Met
M
phenylalani
ne
Phe
F
tryptophan
Trp
AMINO ACID
THREE
LETTER CODE
SINGLE
LETTER CODE
serine
Ser
S
threonine
Thr
T
cysteine
Cys
C
tyrosine
Tyr
Y
asparagine
Asn
N
glutamine
Gln
Q
aspartic acid
Asp
D
glutamic acid
Glu
E
W
proline
Pro
P
lysine
Lys
K
arginine
Arg
R
histidine
His
H
Protein Polymers
 Forming a protein’s polymer chain involves a
condensation reaction between an acid group
(-COOH) and an amine group (-NH2), with water
as a product.
 Structure of a 4 unit amino acid:
Polypeptide Chains
 In a protein the polypeptide chain is the backbone
of the molecule, holding it together by the covalent
bonds (primary bonds)
 Known protein polymers contain from a few dozen
to half-a-million amino acid units
 Proteins have a string-like secondary structure


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Alpha helix structure -- Coiled peptide
Beta configuration ---- parallel strands
Combined structures-- coiled, parallel, and
tangled sections
Hydrogen Bonds
 Hydrogen bond form between O and N atoms
 Alpha helix configuration is held in shape by
H bonds between the C=O group on one loop
and the N-H group across the way.
 H bonds are fairly weak. Any external force
that breaks these bonds simultaneously
destroys the secondary structure, causing the
protein to denature
 For example heating and change in pH
destroys H bond
Changing Proteins thru Other Bonds
 Adding a substance that forms a stronger bond
than H, it changes the shape of the protein.
 For example Lead and Mercury in human body
denatures many of the essential proteins in the
body
 Whole protein molecules cluster in a characteristic
shape or structure. For example, tobacco mosaic
virus molecules form a hollow tube
 Proteins are somewhat water soluble and can be
classified as precipitating colloids