Discussion 3 Flashcards
Which statement is TRUE for RNA but not DNA?
RNA uses 2-deoxyribose sugar.
RNA uses uracil as a nitrogenous base.
RNA is created from DNA in a process known as translation.
RNA is the only nucleic acid that can be absorbed in the UV spectrum.
RNA uses uracil as a nitrogenous base.
RNA occurs primarily as single stranded molecules that can give rise to _______ structures.
diploid
stem-loop
parallel
tautomeric
haploid
stem-loop
Genomic DNA is _____, resulting in the production of _____.
transcribed; mRNA
translated; tRNA
transcribed; protein
translated; protein
translated; rRNA
transcribed; mRNA
Polypeptide synthesis proceeds from the _____ to the _____.
entrance site; exit site
50S subunit; 30S subunit
C-terminus; N-terminus
N-terminus; C-terminus
peptidyl site; aminoacyl site
N-terminus; C-terminus
a. Name these three types of RNA____________
rRNA, tRNA, mRNA.
_____________ moves genetic information from the nucleus to the ribosomes in the cytoplasm. ______________ decodes the genetic message; it matches sequences of three nucleotides to amino acids. __________________is involved in the catalysis of amide bond formation.
mRNA, tRNA, rRNA.
In bacteria, riboflavin can inhibit its own synthesis by binding to an mRNA element termed a _____________
riboswitch.
RNA interference is a mechanism of post-transcriptional RNA-dependent ______.
chromatin-remodeling
gene silencing
histone methylation
coactivation
apoptosis
gene silencing
What is the region immediately adjacent to the starting site for RNA polymerization called?
promoter
enhancer
initiator
consensus sequence
TF binding site
promoter
Two amino acids of the standard 20 contain hydroxyl-groups. They are:
cysteine and serine.
cysteine and threonine.
methionine and cysteine.
methionine and serine.
threonine and serine.
threonine and serine.
At a pH above its pKa, the phenol group of tyrosine is_______________
deprotonated.
A typical protein weighs ________ daltons.
50
500
5000
50,000
50,000
Which statement is most TRUE regarding peptide bonds?
They are amide linkages that connect amino acids.
They are flexible linkages that rotate around the sp2 bond in the carbonyl carbon.
They are composed of an electronegative carbonyl group and an electropositive nitrogen atom.
They are weaker than London dispersion forces.
They are amide linkages that connect amino acids.
In the tripeptide Lys-Pro-Ile, the C-terminal residue is____________
Ile.
The formation of a dipeptide from two amino acids involves
side-chain complementarity.
loss of water.
oxidation of the α-carbon.
reduction of the α-carbon.
base catalysis.
loss of water.
Which one of the following statements about peptide bonds is FALSE. Peptide bonds are:
rigid and planar, with partial double-bond character.
charged.
covalent.
involved in forming the primary structure of proteins.
amides.
charged.
Which of the following statements BEST describes a prosthetic group?
They are nonpeptide molecules or ions critical to a protein’s structure.
They are short peptide chains attached to a larger protein.
They are nonfunctional components of a protein.
They are the active part of an enzyme.
They are nonpeptide molecules or ions critical to a protein’s structure.
Which of the following are methods of denaturing a protein?
pH changes
heat
mechanical agitation
all of the above
all of the above
Why do detergents denature proteins?
The primary structure of the protein can cause alterations in the charges of the residues.
The secondary structure can be altered because of disruptions in the hydrogen bonding.
The forces stabilizing the tertiary structure are disrupted, changing the conformation of the protein.
The quaternary structure can be modified because of the deprotonation of prosthetic groups.
The forces stabilizing the tertiary structure are disrupted, changing the conformation of the protein.
Two cysteine residues would most likely result in what type of bonding?
hydrogen bond
disulfide bond
dispersion forces
salt bridge
disulfide bond
The simplest protein structure is __________ structure.
primary
secondary
tertiary
quarternary
primary
The overall charge of the polypeptide His-Tyr-Lys-Met-Ile-Glu at pH 6.9 is ___?
–2
–1
0
+1
+2
0
Which level of protein structure is defined as “the hydrogen bonded arrangement of the polypeptide backbone”?
Primary
Secondary
Tertiary
Quaternary
Secondary
Why does a decrease in pH alter/disrupt the tertiary structure of an enzyme?
It reduces disulphide bonds.
It promotes proteolytic cleavage of peptide bonds.
It disrupts ion pairs/salt bridges.
It reduces hydrophobic interactions.
It deprotonates prosthetic groups.
It disrupts ion pairs/salt bridges.
Zwitterions are _____.
amino acids
ionic molecules that are racemic
ions that bear both negatively and positively charged groups
side-chain carboxylate anions
delocalized ions
ions that bear both negatively and positively charged groups
Which of the 20 standard amino acids is optically inactive?
Arg
Pro
Ile
Gly
Cys
Gly
Which of the following amino acids has a charged polar side chain at pH 7.0?
Leu
Ala
Met
Trp
Glu
Glu
Which of the following amino acids has a sulfur atom in its side chain?
Asn
Ser
Phe
Met
Tyr
Met
At a pH above its pKa, the R-group of Asp is _____.
protonated and neutral
protonated and positively charged
deprotonated and neutral
deprotonated and negatively charged
none of the above
deprotonated and negatively charged
Leucine has a ___________side chain; glutamate has a ____________ side chain.
Non-polar, charged.
At physiological pH, all amino acids have at least _____ charged groups.
0
1
2
3
cannot be determined
2
a. How many different amino acids can be incorporated into proteins during translation?
20
b. Do ribosomes use L or D amino acids for protein synthesis?
L
Choose amino acid(s) and amino acid derivative(s) that can act as neurotransmitter. Select all that apply.
glycine
glutamate
γ-aminobutyric acid (GABA)
proline
valine
glycine
glutamate
γ-aminobutyric acid (GABA)
The peptide AYDG has an N-terminal _________ residue.
glycine
glutamic acid
glutamine
aspartic acid
alanine
alanine
Which of the following tripeptides would be expected to be the most hydrophobic?
KYG
KYA
GYA
DYA
DYG
GYA
The predominant noncovalent interaction seen in α helices and β sheets is _____.
electrostatic interaction
hydrogen bond
dipole–dipole interaction
hydrophobic interaction
all of the above
hydrogen bond
Which of the following amino acids is generally absent from an α helix?
Trp
Ser
Ile
Pro
none of the above
Pro
α helices and β sheets constitute _____ structure.
primary
secondary
tertiary
quaternary
none of the above
Secondary
Which of the following best describes the peptide backbone in a β sheet?
coiled
compacted
highly extended
rigid
none of the above
highly extended
In a protein, the most conformationally restricted amino acid is ______; the least conformationally restricted is ______.
Trp, Gly
Met, Cys
Pro, Gly
Ile, Ala
Ala, Pro
Pro, Gly
