Chapter 20 - Proteins
essential amino acid
a standard amino acid needed for protein synthesis that must be obtained from dietary sources because the human body cannot synthesize it in adequate amounts from other substances
protein
a peptide in which at least 40 amino acid residues are present
multimeric protein
a protein in which more than one peptide chain is present
simple protein
a protein in which only amino acid residues are present
monomeric protein
a protein in which only one peptide chain is present
beta pleated sheet structure
a protein secondary structure in which two fully extended protein chain segments in the same or different molecules are held together by hydrogen bonds
unstructured protein segment
a protein secondary structure that is neither an alpha helix nor a beta pleated sheet
polar neutral amino acid
an amino acid that contains one amino group, one carboxyl group, and a side chain that is polar but neutral
alpha Keratin
- abundant in nature - found in protective coatings for organisms
collagen
- most abundant of all proteins in humans - major structural material in tendons, ligaments, blood vessels, and skin - organic component of bones and teeth
electrostatic interactions
- salt bridges - involve the ineraction between an acidic side chain and a basic side chain
disulfide bonds
- strongest of the tertiary-structure interactions - result from the -SH groups of two cysteine residues reacting with each other to form a covalent disulfide bond
b.
Aspartic acid, an acidic amino acid, can have four different forms in solution. These four forms are given in the response list. Select from the response list the form of aspartic acid that will be dominant in a solution of pH 3.
c.
Aspartic acid, an acidic amino acid, can have four different forms in solution. These four forms are given in the response list. Select from the response list the form of aspartic acid that will be dominant in it's zwitterion form.
b.
Glycine, the simplest amino acid, is different from all of the other standard amino acids in that it a. does not have a chiral center b. more than one correct response c. has a side chain that does not contain carbon d. occurs naturally as a D-isomer rather than as a L-isomer
d.
R-group interaction between which of the following pairs of amino acids produces a disulfide bond? a. alanine-glycine b. proline-proline c. more than one correct response d. cysteine-cysteine
peptide bond
a covalent bond between the carboxyl group of one amino acid and the amino group of another amino acid
polypeptide
a long unbranched chain of amino acids
zwitterion
a molecule that has a positive charge on one atom and a negative charge on another atom, but which has no net charge
protein
a naturally occurring, unbranched polymer in which the monomer units are amino acids
prosthetic group
a non-amino acid group present in a conjugated protein
alpha helix structure
a protein secondary structure in which a single protein chain adopts a shape that resembles a coiled spring, with the coil configuration
conjugated protein
a protein that has one or more non-amino acid entities present in its structure in addition to one or more peptide chains
membrane protein
a protein that is found associated with a membrane system of a cell
fibrous protein
a protein whose molecules have an elongated shape with one dimension much longer than the others
globular protein
a protein whose molecules have peptide chains that are folded into spherical or globular shapes
b.
a total of six isomeric tetrapeptides can be made from which of the following combinations of amino acids? a. more than one correct response b. Gly, Gly, Val, and Val c. Val, Val, Val, and Ala d. Ala, Ala, Val, and Gly
alpha-amino acid
an amino acid in which the amino group and the carboxyl group are attached to the alpha-carbon atom
polar acidic amino acid
an amino acid that contains one amino group and two carboxyl groups, the second carboxyl group being part of the side chain
nonpolar amino acid
an amino acid that contains one amino group, one carboxyl group, and a nonpolar side chain
polar basic amino acid
an amino acid that contains two amino groups and one carboxyl group, the second amino group being part of the side chain
amino acid
an organic compound that contains both an amino group and a carboxyl group
peptide
an unbranched chain of amino acids
a.
aspartic acid, an acidic amino acid, can have four different forms in solution. these four forms are given in the response list. select from the response list the form of aspartic acid that will be dominant in a solution of pH 11
d.
determine the structural level (primary, secondary, etc) associated with the protein characteristics of the alpha-helix configuration a. tertiary structure b. quaternary structure c. primary structure d. secondary structure
d.
determine the structural level associated with the protein characteristics of the hydrogen bonding between amide hydrogen atoms and carbonyl oxygen atoms a. primary structure b. quaternary structure c. tertiary structure d. secondary structure
b.
determine the structural level associated with the protein characteristics of the three-dimensional shape resulting from R-group interactions. a. quaternary structure b. tertiary structure c. secondary structure d. primary structure
myoglobin
globular protein that functions as an oxygen storage molecule in muscles
hemoglobin
globular protein that transports oxygen from the lungs to tissue
a.
how many different tripeptides can be formed from two molecules of leucine (Leu) and one molecule of glutamic acid (Glu)? a. three b. five c. four d. two
c.
how many peptide linkages are present for the pentapeptide Gly-Ala-Gly-Gly-Ala? a. two b. three c. four d. zero
a.
in the tetrapeptide Phe-Gln-Trp-His, the C-terminal amino acid is a. His b. Trp c. Phe d. Gln
a.
in which of the following pairs of proteins are both members of the pair fibrous proteins? a. alpha-keratin and collagen b. collagen and hemoglobin c. hemoglobin and myoglobin d. more than one correct response
b.
interactions between amino acid R groups is responsible for which of the following levels of protein structure? a. primary b. tertiary c. both secondary and tertiary d. secondary
standard amino acid
one of the 20 alpha-amino acids normally found in proteins
d.
parallel polypeptide chains in a beta-pleated sheet conformation are held together by a. more than one correct response b. covalent bonding c. R-group interactions d. hydrogen bonding
isomeric peptide
peptide containing same amino acids present in different order (constitutional isomers)
b.
proteins are polymers in which: a. alternating amino acid and glucose monomer units are present b. unbranched chains of amino acids are present c. both unbranched and branched chains of amino acids are present d. branched chains of amino acids are present
enzymes
proteins with the role of biochemical catalyst
c.
quaternary structure is possible for a protein only when: a. a protein chain bends back on itself b. all amino acids have nonpolar R groups c. two or more protein chains are present d. the amino acid cysteine is present
hydrophobic interactions
result when two nonpolar side chains are close to each other
secondary protein structure
the arrangement in space adopted by the backbone portion of a protein
a.
the complete hydrolysis of a protein produces a mixture of a. free amino acids b. polypeptides and free amino acids c. dipeptides and free amino acids d. polypeptides
b.
the joining together of two amino acids to form a dipeptide involves the reaction between a. an alpha-carbon and a hydroxyl group b. an amino group and a carboxyl group c. two amide groups d. an amino group and an alpha-carbon
b.
the non-amino acid portion of a conjugated protein is called a a. hydrophilic group b. prosthetic group c. hydrophobic group d. side chain
primary protein structure
the order in which amino acids are linked together in a protein
quaternary protein structure
the organization among the various peptide chains in a multimeric protein
tertiary protein structure
the overall three-dimensional shape of a protein that results from the interactions between amino acid side chains that are widely separated from each other within a peptide chain
isoelectric point
the pH at which an amino acid exists primarily in its zwitterion form -carry zero net charge
protein denaturation
the partial or complete disorganization of a protein's characteristic three-dimensional shape as a result of disruption of its secondary, tertiary, and quaternary structural interactions
amino acid residue
the portion of an amino acid structure that remains, after the release of H2O, when an amino acid participates in peptide bond formation as it becomes part of a peptide chain
coagulation
the precipitation out of biochemical solution of denatured protein
d.
what is the number of possible different dipeptides produced by partial hydrolysis of the pentapeptide Gly-Ala-Gly-Gly-Ala? a. two b. zero c. one d. three
b.
what is the number of possible different tripeptides produced by denaturation of the pentapeptide Gly-Ala-Gly-Gly-Ala? a. three b. zero c. four d. two
c.
what is the number of possible different tripeptides produced by partial hydrolysis of the pentapeptide Gly-Ala-Gly-Gly-Ala? a. two b. zero c. three d. four
renaturation
when conditions under which the effects of denaturation can be reversed. protein is "refolded" in restoration process
cauterization
when heat is used to seal small blood vessels
b.
which level of protein structure is the sequence of amino acids in a protein directly related? a. quaternary b. primary c. tertiary d. secondary
c.
which of the following levels of protein structure is not disrupted when protein hydrolysis occurs? a. tertiary structure b. primary structure c. no correct response d. secondary structure
d.
which of the following statements concerning proteins is correct? a. some, but not all, multimeric proteins are also conjugated proteins b. some, but not all, globular proteins are also multimeric proteins c. all monomeric proteins are also simple proteins d. more than one correct response
