V. proteins are macromolecules that are polymers formed from
amino acids monomers A. proteins have great structural diversity
and perform many roles B. roles include enzyme catalysis, defense,
transport, structure/support, motion, regulation; protein structure
determines protein function
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C. proteins are polymers made of amino acid monomers linked
together by peptide bonds 1.amino acids consist of a central or
alpha carbon; bound to that carbon is a hydrogen atom, an amino
group (-NH 2 ), a carboxyl group (-COOH), and a variable side group
(R group) the R group determines the identity and much of the
chemical properties of the amino acid
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there are 20 amino acids that commonly occur in proteins; pay
attention to what makes an R group polar, nonpolar, or ionic
(charged) and thus their hydrophobic or hydrophilic nature
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plants and bacteria can usually make their own amino acids;
many animals must obtain some amino acids from their diet
(essential amino acids )
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2.the peptide bond joins the carboxyl group of one amino acid
to the amino group of another; is formed by a condensation reaction
2.two amino acids fastened together by a peptide bond is called a
dipeptide, several amino acids fastened together by peptide bonds
are called a polypeptide
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D. the sequence of amino acids determine the structure (and
thus the properties) of a protein E. proteins have 4 levels of
organization or structure 1.primary structure (1 ) of a protein is
the sequence of amino acids in the peptide chain
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2.secondary structure (2 ) of a protein results from hydrogen
bonds involving the backbone, where the peptide chain is held in
structures, either a coiled -helix or folded -pleated sheet;
proteins often have both types of secondary structure in different
regions of the chain
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3. tertiary structure (3 ) of a protein is the overall folded
shape of a single polypeptide chain, determined by secondary
structure combined with interactions between
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4.quaternary structure (4 ) of a protein results from
interactions between two or more separate polypeptide chains the
interactions are of the same type that produce 2 and 3 structure in
a single polypeptide chain when present, 4 structure is the final
three- dimensional structure of the protein (the protein
conformation) example: hemoglobin has 4 polypeptide chains not all
proteins have 4 structure
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Tertiary Structure of Hemoglobin
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5.ultimately the secondary, tertiary, and quaternary structures
of a protein derive from its primary structure, but molecular
chaperones may aid the folding process 6.protein conformation
determines function
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7.denaturation is unfolding of a protein, disrupting 2 , 3 ,
and 4 structure changes in temperature, pH, or exposure to various
chemicals can cause denaturation denatured proteins typically
cannot perform their normal biological function denaturation is
generally irreversible
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F. enzymes are biological substances that regulate the rates of
the chemical reactions in living organisms; most enzymes are
proteins (covered in some detail later in this course) G. related
compounds amino acids; modified amino acids; polypeptides too short
to be considered true proteins; and modified short
polypeptides