An individual molecule of glycine possesses ________ carbon(s), and an individual molecule of alanine possesses _______ carbon (s).
2,2
1,2
2,1
2,3
3,2
A recent study found that polyQ aggregation can interfere with the clearance of misfiled proteins in the cytosol. PolyQ is a serial repeat of _____________ residues.
Arginine
Glycine
Glutamate
Ubiquitin
Glutamine
With the exception of glycine, all the standard proteinogenic amino acids __________
Contain an optically inactive alpha carbon
Do not exhibit chirality
Are found in biological systems in equal ratios of the two superimposable stereoisomeric conformations
All of the above are true
None of the above are true
_______________ is formed by post-translational modification of the collagen molecule.
Proline
Hydroxyproline
Pyrrolysine
Selenocysteine
Gamma-carboxyglutamate
Phosphates cannot normally be attached to ________________ .
Asparagine
Serine
Threonine
Phosphates cannot be attached to any of the above
Phosphates can be attached to all of the above
At neutral pH, the side chains of __________ are charged.
Lysine
Aspartic acid
The side chains of all of the above are charged
The side chains of none of the above are charged
Which of the following bonds in a peptide exhibits the greater amount of free rotation?
The bond between the carbonyl carbon and the nitrogen of the peptide bond
The bond between the alpha carbon and the alpha-amino (the amino group attached to the central carbon of an amino acid)
A decapeptide (peptide composed of 10 amino acids) contains ______ peptide bonds. _____________ of these peptide bonds possess polarity and also partial double bond character.
Two, None
Nine, Nine
Ten, None
Eleven, Ten
Nine, None
A disulfide bond can be formed by the _________ of two _________
Reduction, selenocysteines
Oxidation, selenocysteines
Reduction, cystines
Oxidation, cystines
None of the above
Serotonin is synthesized from an amino acid precursor. This amino acid is ____________.
Tyrosine
Histidine
Cysteine
Tryptophan
An alpha-helix is stabilized by __________________.
Hydrogen bonding between peptide-bond carbonyl oxygens and amide hydrogens
Disulfide bond formation between cysteine residues located 4 amino acids away from each other
Hydrophobic interactions between non polar side chains
All of the above
A(n) _______________ can be formed from two or more separate polypeptide chains (or segments of polypeptide chains) arranged either in a parallel or in an anti-parallel manner relative to each other.
Alpha-helix
Beta-sheet
Both alpha and beta
Neither alpha nor beta
_________ structure can be possibly stabilized by covalent bonds, hydrophobic interactions, hydrogen bonds, or ionic interactions
Tertiary
Quaternary
Both T and Q
Neither T nor Q
A monomeric protein is denatured by exposure to a chaotropic agent. This act of denaturation can result in the unfolding and disorganization of the protein's ____________.
Secondary
Both
Neither
Which of the following statements about beta-amyloid is (are) true?
It is a highly denatured peptide that consists of many different random conformations
It is associated with the deposition of plaques inside certain key neurons
It always results from a genetically encoded amino acid substitution
Which of the following statements about prions is (are) true?
The prion genome consists of a single molecule of RNA
The prion genome codes for an inherently unstable peptide
Both statements are true
Neither statement is true
One is comparing the noninfectious, normal PrP in a healthy brain to the infectious PrP. The infectious PrP ___________ relative to the normal PrP
Exhibits less resistant to proteolytic degradation
Exhibits a greater tendency to form insoluble aggregates of fibrils
The reaction A-B + water ---> A-OH + B-H is enzymatically mediated by a(n) ___________.
Isomerase
Ligase
Transferase
Hydrolase
An enzyme binds its substrate under optimal conditions. Upon this binding, which of the following will subsequently occur?
An enzyme-substrate complex is produced
Binding of the substrate causes a conformational change in the enzyme
Enzyme-substrate complex is converted to an enzyme-product complex
All statements are true
None are true
An enzyme functions by ______________
Increasing the free energy of activation
Decreasing the free energy of the reactants
Increasing the free energy of the product
None of the statements are true
Which of the following statements about the tau protein is (are) true?
The normal version of tau helps in the assembly and stabilization of the intracellular micro tubular structure
The abnormal tau results from the substitution of a valine to a glutamate
The abnormal tau is hypophosphorylated (fewer phosphates than normal) and is highly soluble
All are true
Protein X is a large and complex polypeptide. X's secondary and tertiary structure would be potentially altered the most by the substitution of a single ______ for a single ________
arginine, lysine
alanine, valine
glutamate, aspartate
serine, proline
glutamine, asparagine
Which of the following statement(s) about amino acids is (are) correct?
Certain amino acids can function in neurotransmission
Certain neurotransmitters are derived from amino acids
Certain hormones are derived from amino acids
Certain amino acids are not incorporated into proteins (non-proteogenic)
All are correct
Which of the following statements is (are) correct?
Glycine is not a chiral molecule
Glycine can be found in both an L and D form in many human proteins
Glycine has an asymmetric center at the alpha carbon
None are correct
Which of the following amino acids would be least likely to be found on the outside surface of a protein buried inside of a hydrophobic environment?
Phenylalanine
Leucine
Alanine
The formation of a disulfide bond by the oxidation of two ______ residues can contribute to the stability of proteins
Methionine
All options
Which of the following statements about amino acids is (are) correct?
The side chains of certain amino acids contain a carboxylate group
The side chains of certain amino acids contain an amide group
The side chains of certain amino acids contain polar hydroxyl groups, which can serve as sites of attachment for compounds that are not amino acids
Which one of the following statements about protein structure is correct?
Proteins consisting of one polypeptide can have quaternary structure
The formation of a disulfide bond in a protein requires that the two participating cysteine residues by adjacent to each other in the primary sequence of the protein
The stability of quaternary structure in proteins is mainly a result of covalent bonds among the subunits
The denaturation of proteins always leads to irreversible loss of secondary and tertiary structure
The information required for the correct folding of a protein is contained in the specific sequence of amino acids along the polypeptide chain
Which one of the following statements is correct?
The alpha-helix can be composed of more than one polypeptide chain
B-sheets exist only in the anti-parallel form
There are 3.6 amino acids in each turn of an alpha helix
Domains are a type of secondary structure
The alpha-helix is stabilized primarily by ionic interactions between the side chains of amino acids
Which of the following statements about the normal form of PrP is (are) correct?
It has a different gene sequence relative to the infectious form
It has a different amino acid sequence relative to the infectious form
It has fewer B-sheets and more A-helices than the infectious form
It is more resistant to proteolytic degradation than the infectious form
It plays a significant role in the development of Alzheimer disease
A peptide bond:
Has partial double bond character
Is ionized at physiological pH
Is cleaved by agents that denature proteins, such as organic solvents and high concentrations of urea
Is stable to heating in strong acids
Most commonly in the cis configuration
Which of the following statements about the alpha-helix is (are) correct?
The sequence of amino acids in the alpha-helix always shows a predictable pattern of specific amino acids throughout the length of the entire helix
The formation of the alpha-helix is always mediated by the enzymatic activity of enzymes known as alpha-helicases
Approx. 50% of the alpha-helices are found in a parallel configuration, while about 50% are in anti-parallel configuration
Which of the following interactions can cooperate in the stabilization of the tertiary structure:
Ionic interactions between negatively charged and positively charged side chains
Hydrophobic interactions between different non polar side chains
Disulfide covalent linkages between two noncontiguous cysteine residues
All cooperate
None of the options cooperate
Which of the following statements about the neurofibrillary tangles associated with Alzheimer disease is (are) correct?
The neurofibrillary tangles are extra-cellular aggregates that tend to accumulate both in the brain and other regions of the central nervous system
There is significant evidence that these neurofibrillary tangles are usually caused by the ingestion of a pathogenic protein known as tau
The neurofibrillary tangles are generally intertwined with the intra-cellular amyloid plaque
Which of the following is the least likely to be disrupted by denaturation of a protein?
Disulfide bonds
Hydrophobic interactions
Peptide bonds
Weak noncovalent interactions
Hydrogen bonds
The addition of a hydroxyl to __________ produces tyrosine
Valine
This is an optically inactive amino acid
This is the precursor of dopamine, epinephrine, and norepinephrine
An example of an imino acid
Branched chain amino acid
valine
tyrosine
phenylalanine
glycine
proline
Protein P is a protein found inside a lipid environment. Which of the following amino acids would be most likely to be found on the outside surface of P
lysine
isoleucine
asparagine
arginine
Drug D has one ionizable group, an amino group, with a pKa of 9.0. This drug can pass through cell membranes most readily when uncharged. Theoretically, passage of the drug would occur most readily at pH ___________.
2.5
4.5
6.5
7.5
9.3
Which of the following amino acids participates the most in protein buffering of blood?
histidine
alanine
tryptophan
PrP(Sc) is the causative agent of transmissible spongiform encephalopathies because of:
A single point mutation in the gene coding for the PrP(Sc)
The ability of the PrP(Sc) to complex with an infectious molecule of nucleic acid
A higher proportion of alpha-helical structures in the PrP(Sc)
