Chapter 3
which amino acid possesses guanidinium group in the side chain? a) Arginine b) Aspartate c) methionine d) leucine e) serine
A, Arginine contains guanidinium in its side chain.
collagen is a protein whose conformation is characterized by a) a triple helix b) a double alpha-helix c) anti-parallel beta-sheet regions d) mostly random coil regions e) the lack of any stable conformation
A, collagen has a triple helical structure
which interactions may participate in the stabilization of tertiary structures by covalent linking polypeptide chains a) disulfide bonds b) electrostatic interaction c) hydrogen bond e) hydrophobic interaction e) peptide bond
A, disulfide bonds are covalent (peptide bonds are the other covalent option but are only involved in the primary structure).
The following is the structure of which amino acid: 2(CH3)-CH-CH2-CHNH2-COOH? a) leucine d) threonine c) arginine d) valine e) lysine
A, leucine in an alkali AA (remember that isoleucine is too).
which of the following mutations would you expect to cause the most drastic alteration a) replacement of glutamate to lysine b) replacement of valine to alamine c) replacement of aspartic acid to glutamic acid d) replacement of lysine with arganine
A, lysine is a basic AA while glutamate is an acidic amino acid
the formation of a peptide bond a) creates partial double bond character between the 3 atoms b) permits unrestricted rotations about each chemical bond c) places the alpha-carbon in the center of 2 different planes d) retains the chemical properties of typical ester bonds
A, peptide bonds have partial-double bond characterisitics. The "3 atoms" mentioned are the Carbon, Nitrogen and oxygen.
an amino acid found in large amounts in collagen is a) proline b) lysine c) arginine d) asparagine e) histidine
A, proline is found in large quantities in collagen.
which statement below is most correct regarding the alpha helical structure of polypeptide chains in proteins a) it is primarily dependent on hydrogen bonding b) it is primarily dependent on disulfide bridges c) it is found in all proteins d) it refers to adjacent chain in fibrous chains
A, the alpha helix is a common example of secondary structure in proteins and is thus held together mostly by hydrogen bonds
the hydrophobic effect is generally thought to be the result of: a) minimization of the disruption of the normal structure of water by hydrophobic molecules b) repulsive forces between polar water and nonpolar hydrophobic molecules c) maximization of order in the mixture of water and hydrophobic molecules d) all of the above
A, the hydrophobic effect is essentially nonpolar molecules trying to be as far away from the polar water molecules.
the secondary structure of proteins a) is maintained by hydrogen bonds b) refers to proteins consisting of 2 or more subunits held by non-covalent forces c) encompasses any hydrogen-bonded interaction found in proteins d) refers to proteins consisting of one or more polypeptide bonds plus a nonprotein moiety e) is found only in fibrous proteins
A, the secondary structure is held together primarily by hydrogen bonds
which of the following amino acids has more than one carboxyl group? a) Serine b) glutamic acid c) Lysine d) alanine e) methionine
B, glutamic acid has more than one carboxyl group (hence its acidity)
which of the following is responsible for the maintenance of proteins secondary structure? a) salt bridges b) hydrogen bonds c) van der waals forces d) hydrophobic interactions e) disulfide bridges
B, hydrogen bonds are the main component to secondary structures.
which of the following amino acid residues may participate in strong hydrophobic bonding? a) glycine b) Isoleucine c) lysine d) serine e) aspartate
B, isoleucene in has an alkyl side chain and is thus extremely non-polar
the peptide bond has all of the following characteristics except a) plainarity b) freedom to rotate c) polarity d) greater stability in trans configuration e) partial double-bond characteristic
B, the peptide bond has a partial double bond characteristic and thus is unable to rotate freely
the primary structure of a protein refers to its a) ability to form intrachain hydrogen bonds b) amino acid sequences c) folding induces disulfide linkages d) ability to form subunit structures e) ability to form intrerchain hydrogen bonds
B, the primary structure is the amino acid sequence held together through covalent bonding.
which of the following describes the side chain of leucine? a) contains a sulfhydryl group b) contains an alcohol group c) contains a branched chain hydrocarbon d) doesnt have a side chain e) contains an acidic group
C, Leucine is an alkyl group (remember w/ isoleucine).
the alpha helix structure of a protein can be considered an example of: a) quaternary structure b) tertiary structure c) secondary structure d) primary structure e) none of the above
C, alpha helixes and beta-sheets are common examples of secondary structures
A major force that contributes to the conformation of proteins, and in globular proteins, occurs primarily in their interior are? a) hydrogen bonds b) charged dipoles c) hydrophobic interactions d) disulfide bridges e) hydration by water
C, hydrophobic interactions help cause the 3-D structure to take shape.
if gly has a positive charge at a pH of 1, then gly-gly-gly in the same buffer would have which of the charges? a) +3 b) +2 c) +1 d) -1 e) -2
C, the addition of more gly would only cancel out their own charges and the total charge would remain as +1.
an amino acid containing an amide function on its side chain a) proline b) lysine c) arginine d) asparagine e) histidine
D, asparagine has an amide on its side chain
cysteine can be converted to cystine by... a) acylation b) peptide bond formation c) reduction d) oxidation e) esterfication
D, disulfide bonds are formed by oxidation (and broken by reduction).
which of the following describes the side chain of glutamine a) contains a branched hydrocarbon b) contains a sulfhydrol group c) contains a methyl group d) contains an amide
D, glutamine contains an amide group
all of the amino acids are optically acid Except for a) leucine b) alanine c) glycine d) cystine e) lysine
D, glycine has the side chain of R=H, and thus cannot be optically active.
Amino acids are classified according to the nature of their side chain. All of the following are correctly classified EXCEPT: a) serine: polar, uncharged b) glutmine: polar, acidic c) arganine: polar, basic d) histidine: nonpolar, uncharged e) phenylalenine: nonpolar, uncharged
D, histidine is a polar amino acid and has basic properties.
A peptide bond a) contributes atoms to hydrophobic interactions b) exhibits unrestricted rotation around C-N bond c) is formed between the side chains of glu and lys d) is planar and partially ionic
D, peptide bonds are planar because they have partial-double bond characteristics.
which of the following amino acids would be the MOST polar? a) alanine b) proline c) isoleucine d) threonine e)phenylalanine
D, threonine is the MOST polar amongst this set of amino acids (contains a hydroxyl group)
Amino acid side chains which may be involved in hydrogen bonding in protein include a) leucine b) isoleucine c) alanine d) tyrosine e) phenylaline
D, tyrosine has an hydroxyl group (the O is involved in hydrogen bonding)
which of the following groups of amino acid residues would be expected to have all of their side chains in a charged state? a) glu, tyr, asn b) met, cys, lys c) His, Ser, Arg d) asp, His, Tyr e) Arg, Asp, Lys
E, Arg, Asp, Lys would have all of their side chains in a charged state (all are basic AA and thus have + charge)
Identify in the following list the covalent bond commonly found in proteins a) hydrogen bonds b) hydrophobic bonds c) pleated sheets d) electrostatic bond e) disulfide bonds
E, disulfide bonds are covalently formed between a pair of cystine amino acids.
the 3-D structure of protein is maintained by a) disulfide linkages b) hydrophobic bonds c) hydrogen bonds d) Ionic bonds e) all of the above
the tertiary structure of proteins is held together by all of the following bonds: disulfide, hydrophobic, hydrogen, and Ionic.