Download Biologically Important Molecules - Proteins PPT

12/02/2013
Proteins
SBI 4UI
February 2013
Biological Function
Proteins represent an extremely diverse
type of macromolecule, providing such
functions as:
catalyzing chemical reactions
providing structural support
transporting substances in the body
enabling organisms to move
regulating cellular processes
providing defence from disease
Amino Acids
a protein is a macromolecule composed
of amino acid monomers joined by a
peptide bond
an amino acid contains a central carbon
atom that is bonded to four groups of
atoms:
a hydrogen atom
an amino group
a carboxyl group
an R group
Amino Acids
the 20 amino acids can be divided into polar,
non-polar and electrically charged groups
of the 20, eight are essential amino acids,
meaning they cannot be produced by the
human body and must be consumed in the
diet
a polymer composed of many amino acids
linked together is called a polypeptide
Levels of Protein Organization
There are four levels of protein
organization:
Primary Structure
linear sequence of amino acids
Secondary Structure
since the peptide bonds are polar, H-bonding is
possible
polypeptides can form a coil-like shape called an
alpha helix, or a folded fan like shape called a
beta pleated sheet
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Levels of Protein Organization
Levels of Protein Organization
Tertiary Structure
Quaternary Structure
Levels of Protein Organization
complex process of protein folding that determines 3D structure
most occurs naturally as peptide bonds and different
R groups interact
mostly determined by hydrophobic effect
may also involve the assistance of a class of proteins
called molecular chaperones
in proteins made up of a combination of
polypeptides, each with their own primary, secondary
and tertiary structures
Denaturation
under certain conditions (such as
extreme temperature or chemical
exposure), proteins can unfold in a
process known as denaturation
once a protein loses its normal 3-D shape,
it is no longer able to perform its usual
function
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