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Chapter 19
Proteins
75
Chemistry
Undergraduate 1
08/29/2006

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Term
are all proteins structurally similar?
Definition
yes
Term
proteins are polymers consisting of...
Definition
chains of amino acids chemically bound to each other
Term
an amino acid is a compound that contains both a
Definition
amino group and carboxylate group
Term
how many amino acids are commonly found in the body?
Definition
20
Term
what are the amino acids found in proteins called?
Definition
alpha amino acids
Term
why are they called alpha amino acids>
Definition
because they are attached to the alpha carbon
Term
what is the alpha carbon?
Definition
the carbon next to the carboxylate group
Term
what gives an amino acids its unique characteristics
Definition
the R group (or side chain)
Term
what four categories are amino acids broken up into?
Definition
neutral with nonpolar side chains, neutral with polar side chains, basic side chains and acidic side chains
Term
acidic side chains contain a (blank) group
Definition
carboxylate
Term
basic side chains contain an (blank) group
Definition
amino group
Term
what is the simplest amino acid
Definition
glycine
Term
with the exception of glycine, what is true of the alpha carbons in amino acids?
Definition
they are chiral
Term
are most amino acids found in the D or L form?
Definition
L
Term
what is a zwitterion?
Definition
a dipolar ion that carries both a positive and negative charge as a recult of an internal acid-base reaction in an amino acid molecule
Term
what is the net charge of a zwitterion?
Definition
zero
Term
what happens to a zwitterion if an acid is added?
Definition
then the COO- picks up a hydrogen
Term
what happens to a zwitterion if a base is added?
Definition
then the amino group loses a hydrogen
Term
what is the isoelectric point?
Definition
the pH at which the zwitterion forms
Term
what is the only sulfhydryl containing amino acid?
Definition
cysteine
Term
what chemical property do cysteine have that other amino acids don't?
Definition
they are able to be oxidized to form a disulfide bond
Term
what is the product of oxidizing a cysteine?
Definition
a disulfide compound, cystine
Term
what functional group reacts when two amino acids are put together?
Definition
the carboxylate group
Term
what are dipeptides?
Definition
compounds made up of two amino acids
Term
what kind of bonds peptide bonds?
Definition
amide linkages
Term
does the order amino acids are in matter?
Definition
yes
Term
alyclalamine and alanylglycine are (blank) isomers of each other.
Definition
structural
Term
peptide
Definition
an amino acid polymer of short chain length.
Term
polypeptide
Definition
an amino acid polymer of intermediate chain length containing up to 50 amino acid residues
Term
protein
Definition
an amino acid polymer made up of more than 50 amino acids
Term
amino acid residue
Definition
an amino acid that is part of a peptide, polypeptide or protein chain
Term
N-teminal residue
Definition
an amino acid on the end of a chain that has an unreacted or free amino acid
Term
C-terminal residue
Definition
an amino acid on the end of a chain that has an unreacted or free carboxylate group
Term
which side is the N-terminal on?
Definition
the left
Term
disulfide bridge
Definition
a bond produced by the oxidation of -SH groups on two cysteine residues. The bond loops or holds two peptide chains together.
Term
what is the difference in the structure of vasopressin and oxytocin?
Definition
two amino acids
Term
are proteins relatively large or small molecules?
Definition
large
Term
what is one of the most important properties of proteins that is based on its R group?
Definition
acid base behavior
Term
what determines at what pH a protein will clump together?
Definition
the charge on the R group
Term
name eight functions of proteins in the body:
Definition
catalysts, structural, storage, protective, regulatory, nerve impulse transmission, movement, and transport
Term
what are two types of proteins that are based on their structural shape?
Definition
fibrous and globular
Term
fibrous proteins
Definition
made up of long rod shaped molecules that can intertwine with one another and form strong fibers.
Term
are fibrous proteins water soluble?
Definition
no
Term
where are fibrous proteins usually found?
Definition
tissue, hair and skin
Term
globular proteins
Definition
more spherical
Term
are globular proteins soluble in water?
Definition
yes, they either dissolve or form colloidal dispersions in water
Term
what are the two types of proteins based on composition?
Definition
simple and conjugated
Term
simple proteins
Definition
contain only amino acid residues
Term
conjugated proteins
Definition
contain amino acid residues and other organic or inorganic compounds
Term
prosthetic group
Definition
the non amino acid parts of conjugated proteins
Term
what do all proteins have in common?
Definition
carbon nitrogen backbone
Term
what does the primary structure of a protein tell you?
Definition
the order in which amino acid residues are linked together
Term
what causes a protein chain to fold and curl into distinctive shapes that in turn enables the protein to function properly.
Definition
the sequence of amino acids
Term
when a primary structure folds and becomes aligned in a certain orderly pattern, this is called...
Definition
secondary structure
Term
what kind of bonding makes secondary structures?
Definition
hydrogen
Term
what are the two forms secondary structures can take?
Definition
alpha helix and beta sheets
Term
in an alpha helix, what compounds are hydrogen bonded?
Definition
the carbonyl oxygens and amide hydrogens
Term
are all amide groups or all carbonyl oxygens involved in hydrogen bonding?
Definition
all amide groups
Term
what is the less common structure: alpha helix or beta sheets
Definition
beta sheets
Term
where is the only place beta sheets are found extesively?
Definition
silk proteins
Term
what are hydrogen bonded in beta sheets?
Definition
the amide carbonyl oxygens and amide hydrogens
Term
what is tertiary structure?
Definition
the bending and folding of the protein into specific three dimensional shape.
Term
the tertiary structure results from the interactions between
Definition
the R side chains and the amino acid residues
Term
what are the four types of R group interactions
Definition
disulfide bridges, salt bridges, hydrogen bonds, and hydrophobic interactions
Term
what two residues can a disulfide linkage occur between
Definition
cysteine
Term
are disulfide linkages present in secondary structures?
Definition
no
Term
what are salt bridges?
Definition
a result of ionic bonds that form between the ionized side chain of an acidic amino acid and the side chain of a basic amino acid
Term
what is the difference between the hydrogen bonds of the tertiary structure and the hydrogen bonds of the secondary structure?
Definition
in the secondary structure the bonding is between backbone carbonyl and amide groups, in the tertiary structure, it is between the R groups
Term
hydrophobic interactions
Definition
result when nonpolar groups are either attracted to one another or forced together by their mutual repulsion of an aqueous solution
Term
what is the weakest of the four types of bonds?
Definition
the hydrophobic interactions
Term
quaternary structure
Definition
arrangement of subunits
Term
what is a subunit
Definition
a polypeptide chain
Term
if proteins are exposed to physical or chemical conditions such as extreme temperatures or pH values, what happens?
Definition
denaturation
Term
what happens during denaturation?
Definition
folded structure breaks down and the protein takes on a random disorganized conformation
Term
what else, besides heat and pH cause denaturation?
Definition
heavy metal ions
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