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LIPIDS
-Fats , oils, Steroids, waxes, Phospholipids.
Most common property;
Insolubility in water .
Hydrophobic in nature.
Lipids are not polymers, but a macromolecule
Functions:
Fats and oils are biological fuels (store energy)
Components of membranes.
Hormones, fat soluble vitamins, Light absorbing
pigments.
Fats serve as thermal insulation, waxes on leaf
serve as water repellent
FATS or SIMPLE FATS.
Made up of
a. Glycerol
b. Fatty acids
FATS
• Fatty acid
-consists of a carboxylic
Group and
-A long hydrocarbon
chain
(C4 to C18)
-hydrophobic due to
hydrocarbon chain
FATS, , TRIGLYCERIDE
• 3 fatty acid chains linked to a glycerol molecule
via an ester linkage called
• TRIACYLGLYCEROL OR TRIGLYCERIDE OR FATS .
• FATS are esters of Glycerol
and fatty acids
Saturated fatty Acid
No double bonds in C-C skeleton
Fat made from saturated fatty acid is called a
saturated fat
Animal fats are saturated .ex Butter
Unsaturated Fatty acid
• An unsaturated fatty acid has one or more
double bonds
• Produce a kink or bending in the structure.
• fats of plants and fishes – liquids at room
temperature --OILS
• Ex: Cod liver oil, Groundnut oil
Phospholipids
– Phospholipids
• Glycerol molecule
with…
• 2 fatty acid chain
AND
• A phosphate
group – polar or
hydrophilic
Chapter 7: Membrane structure and
function
PHOSPHOLIPIDS
• Hydrophilic
Region:phospholipid
head is polar and it
is associated with
water molecules
• Hydrophobic Region
: long FATTY ACID
TAIL IS nonpolar.
Major components of all CELL
MEMBRANEs
STEROIDS
• Steroids consist of
carbon skeleton of four
fused ring
• Different functional
groups attached to it
Cholesterol
• Present in animal
membranes
• Is the precursor for sex
hormones, bile acids
High % of cholesterol in blood may cause
atherosclerosis.
LIPIDS
• Compare the structure of a fat ( triglyceride)
with that of a phospholipid
• How do saturated fats differ from unsaturated
fats both in structure and in function
• Why are human sex hormones considered to
be lipid.
PROTEINS
Amino acids
• Amino acids are the building blocks of
proteins.
• Proteins are built from a repertoire of 20
amino acids
Glycine : Gly
Amino acid
Central carbon is referred to as α carbon.
Linked to
1. Carboxylic acid group (COOH)
2.Amino group (N H2)
3.Hydrogen atom and
4.R is the variable component -the
side chain
CORN
Glycine has H atom
Aromatic amino acids
Glycine is the smallest a.a.
It is the only a.a. which is not
having a chiral C atom.
The sulfhydryl( -S-H) group of two
cysteine can react to form a covalent
disulfide bridge(-S-S) -a Cystine
molecule
The side chain of Proline is covalently
linked back to Amino group.
• Essential amino acid
• -supplied by dietary
protein
• Try, Lys, Met, Phe, Thr,
val, Leu& Iso
• Non essential amino
acid
-synthesis by the body.
-ala, asp, cys, Glu, Gly,
Pro, ser, Tyr
Mnemonic for semiessential and essential
a.a.
PVT TIM HALL.
(Phe, Val, Thr, Trp, Ile, Met, His, Arg, Leu &
Lys)
What are proteins
• Proteins are polymers of amino acids in
which the adjacent amino acids are
connected by peptide bonds.
Peptide Bonds
Peptide bonds
a C-N covalent bond
between the carboxyl group(-COOH) of one
amino acid
And
the Amino( NH2 ) group of an adjacent amino
acid
Polypeptide
Polymer of many amino acids linked by
peptide bond.
• Each polypeptide has N-terminal and C
terminal.
Protein
• Protein conformation is defined by its
sequence of a.a. residues , which determines
the function.
• 3D- structure of a protein is determined by
The characterisitics & interactions of the side
chains in it’s a.a. sequence .
Protein: glucagon -29 residues
Lysozyme - 129 residues mol wt. 13,930
Linus Pauling
(February 28, 1901 – August 19,
1994)
Structure of chemical bonds
& structure of molecules
Nobel prize for chemistry
Nobel Prize for Peace
Explained the structure of
alpha helix of proteins
Example
of
Transthyretin
Primary Structure
C-terminus
N-terminus
Linear arrangement or sequence of amino acids linked by
peptide bond
Determined by genetic information
Secondary
structure
a helix
• Polypeptide chains fold
into regular structures such
as the alpha helix, the beta
sheet
• Hydrogen bonds stabilizes
the secondary structures.
In alpha Helix
• all the main chain - CO and
-NH groups are hydrogen
bonded.
Secondary
structure
a helix
alpha Helix coiled structure
stabilized by intrachain
hydrogen bonds.
• all the main chain - CO and
-NH groups are hydrogen
bonded.
Hydrogen Bonding in H20
O atom
H atom
A hydrogen bond forms when a hydrogen atom covalently bonded to one
Electronegative atom is also attracted to another electronegative atom .In living
Cells, the electronegative partners are usually oxygen or nitrogen atoms.
Secondary structure
• b sheet
B Sheet consists
of beta strands
connected laterally
by five or more
hydrogen bonds,
forming a twisted,
pleated sheet
Ex :β –keratins in claws, scales ,
feathers , beaks & silk is made up of beta
sheets.
Tertiary structure
Is the 3D structure of a protein
Tertiary structure
• Is the 3D structure of a
protein
• Interactions between
the side chains of the
amino acids.
• Hydrophobic
interactions, ionic bond
and vanderwaals
interactions are involved.
Tertiary structure of 6 different
proteins
Orange color
shows ----Beta
sheets.
Blue color
shows alpha
helix.
Quaternary Structure
• Proteins consisting of
more than one
polypeptide chain
display quaternary
structure.
• Each polypeptide chain
is called a subunit.
Examples of quaternary structure.
Haemoglobin- 4 polypeptide chains
2 alpha ,2betachains
-globular protein
Collagen-Triple Helix,
Proteins
• Function as catalysts.
• Mechanical support
• Immune protection
• Interact with other biological macromolecules
To form macromolecular assemblies
each type of protein has a unique 3Dstructure or conformation
Structure determines function
Protein Denaturation
• Loss of three dimensional structure of the Protein
causes loss of biological function.
Ex: salt concentration, extremes of pH, thermal energy
from heat, organic solvents alcohol or acetone.
boiling of egg.
Renaturation: certain proteins denatured by heat or
denaturing agents regain their native structure
Protein folding
• Protein folding in cell is assisted by a class of
proteins chaperonin.
Refer chapter 2 & 3 (Biology- campbell ) polar, nonpolar
covalent bond, hydrogen bond , hydrophilic & hydrophobic
character .
- For understanding the concept ( not in syllabus)
BONDING
IONIC BONDING
COVALENT BONDING
non-polar
covalent
and
polar covalent
Bonding
Covalent bonding
Polar covalent bond
Bonding
Covalent bonding
Polar covalent bond – unequal sharing of
electrons
A great example of a molecule with polar
covalent bonds is water. Why is water
considered polar?
What is a partial positive and partial
negative charge?
Bonding
Covalent bonding
Non-polar covalent bond – equal sharing of
electrons.hydrophobic
Polar covalent bond – unequal sharing of
electrons. Hydrophilic.
Bonding
Ionic bonding – Atoms transfer or accept electrons from one another
The sodium ion and the chloride ion will be attracted to each other and
form an ionic bond.
Na +
Cl -
The ionic bond is due to the attractive forces between the now
positively charged sodium & the negatively charged chloride.
Bonding
Electronegativity is the tendency of an atom
to attract electrons.
If the electronegativity of an atom is high,
then it attracts and holds on to electrons.
If the electronegativity of an atom is low, then
it tends to give electrons away.