Chemistry Class with Dr. Z.
P.O. Box 44
Old Greenwich, CT 06870
.
Phone: 203 698 0429
Fax: 203 698 0312
E-Mail:
techserv@zenitech.com
As the cosmetic industry becomes more and more oriented toward natural
products, proteins, polypeptides and amino acids are more and more
important. Dr. Z is pleased to present the following information on amino
acids.
PROTEIN1
Protein is a large, complex molecule composed of amino acids. The sequence of the
amino acids, and thus the function of the protein, is determined by the sequence of the
base pairs in the gene that encodes it. Proteins are essential to the structure, function, and
regulation of the body. Examples are hormones, enzymes, and antibodies. Many
bodybuilders use Protein to help build muscle in the body.
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Amino Acids2
Name
Abbr.
Linear structure formula
======================================================
Alanine
ala a
CH3-CH(NH2)-COOH
Arginine
Asparagine
arg r
asn n
Aspartic acid asp d
Cysteine
Glutamine
cys c
gln q
Glutamic acid glu e
Glycine
gly g
HN=C(NH2)-NH-(CH2)3-CH(NH2)-COOH
H2N-CO-CH2-CH(NH2)-COOH
HOOC-CH2-CH(NH2)-COOH
HS-CH2-CH(NH2)-COOH
H2N-CO-(CH2)2-CH(NH2)-COOH
HOOC-(CH2)2-CH(NH2)-COOH
NH2-CH2-COOH
Histidine
his h
NH-CH=N-CH=C-CH2-CH(NH2)-COOH
|__________|
Isoleucine
ile i
CH3-CH2-CH(CH3)-CH(NH2)-COOH
Leucine
leu l
(CH3)2-CH-CH2-CH(NH2)-COOH
Lysine
lys k
H2N-(CH2)4-CH(NH2)-COOH
Methionine
met m
CH3-S-(CH2)2-CH(NH2)-COOH
Phenylalanine phe f
Ph-CH2-CH(NH2)-COOH
Proline
pro p
Serine
ser s
HO-CH2-CH(NH2)-COOH
Threonine
thr t
CH3-CH(OH)-CH(NH2)-COOH
Tryptophan
trp w
Tyrosine
tyr y
Valine
val v
NH-(CH2)3-CH-COOH
|__________|
Ph-NH-CH=C-CH2-CH(NH2)-COOH
|_______|
HO-p-Ph-CH2-CH(NH2)-COOH
(CH3)2-CH-CH(NH2)-COOH
2
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Proteins
Proteins are macromolecules. They are constructed from one or more un-branched chains
of amino acids; that is, they are polymers. A typical protein contains 200–300 amino
acids but some are much smaller (the smallest are often called peptides, but are none the
less still proteins) and some much larger (the largest to date is titin a protein found in
skeletal and cardiac muscle; it contains 26,926 amino acids in a single chain!).
Every function in the living cell depends on proteins.

Motion and locomotion of cells and organisms depends on contractile proteins.
[Examples: Muscles]

The catalysis of all biochemical reactions is done by enzymes, which contain
protein.

The structure of cells, and the extracellular matrix in which they are embedded, is
largely made of protein. [Examples: Collagens] (Plants and many microbes
depend more on carbohydrates, e.g., cellulose, for support, but these are
synthesized by enzymes.)

The transport of materials in body fluids depends of proteins. [See Blood]

The receptors for hormones and other signaling molecules are proteins.

Proteins are an essential nutrient for heterotrophs.

The transcription factors that turn genes on and off to guide the differentiation of
the cell and its later responsiveness to signals reaching it are proteins.

and many more — proteins are truly the physical basis of life.
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Summary3
The Amino Acids. All proteins are polymers of amino acids, which are bifunctional
organic compounds that contain both an amino group and a carboxylate group.
Differences in the R groups of amino acids cause differences in the properties of amino
acids and proteins.
Zwitterions. The presence of both amino groups and carboxyl groups in amino acids
makes it possible for amino acids to exist in several ionic forms, including the form of a
zwitterion. The zwitterion is a dipolar form in which the net charge on the ion is zero.
Reaction of Amino Acids. Amino acids can undergo reactions characteristic of any
functional group in the molecule. Two reactions of importance are the reaction of two
cysteine molecules to form a di sulfide, and the reaction of amino groups and carboxylate
groups of different molecules to form peptide (amide) linkages.
Important Peptides. More than 200 peptides have been shown to be essential to the
proper functioning of the human body. Hormones and enkephalins are among the
peptides for which functions have been identified.
Characteristics of Proteins. Proteins are large polymers of amino acids. Acidic and
basic properties of proteins are determined by the acidic or basic character of the R
groups of the amino acids comprising the protein. Proteins perform numerous important
functions in the body. Proteins are classified structurally as fibrous or globular. They are
classified on the basis of composition as simple or conjugated.
The Primary Structure of Proteins. The primary structure of a protein is the sequence
of amino acids in the polymeric chain. This gives all proteins an identical backbone of
carbon and nitrogen atoms held together by peptide linkages. The difference in proteins is
the sequence of R groups attached to the backbone.
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The Secondary Structure of Proteins. Protein chains are held in characteristic shapes
called secondary structures by hydrogen bonds. Two specific structures that have been
identified are the alpha-helix and the beta-pleated sheet.
The Tertiary Structure of Proteins. A third level of complexity in protein structure
results from interactions between the R groups of protein chains. These interactions
include disulfide bridges, salt bridges, hydrogen bonds, and hydrophobic attractions.
The Quaternary Structure of Proteins. Some functional proteins consist of two or
more polypeptide chains held together by forces such as ionic attractions, disulfide
bridges, hydrogen bonds, and hydrophobic forces. The arrangement of these polypeptides
to form the functional protein is called the quaternary structure of the protein.
Protein Hydrolysis and Denaturation. The peptide (amide) linkages of peptides and
proteins can be hydrolyzed under appropriate conditions. This destroys the primary
structure and produces smaller peptides or amino acids. The characteristic secondary,
tertiary, and quaternary structures of proteins can also be disrupted by certain physical or
chemical conditions such as extreme temperatures or pH values. The disruption of these
structures is called denaturation, and causes the protein to become nonfunctional and, in
some cases, to precipitate.
References
1. http://protein.medical-information.org/
2. http://www.chemie.fu-berlin.de/chemistry/bio/amino-acids_en.html
3. http://ull.chemistry.uakron.edu/genobc/Chapter_19/
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