Cell Structure & Fn Exam #4 Practice 27 Questions with Verified Answers
Mutations that alter sequences near the 5′ end of mRNA result in alterations
... [Show More] near the corresponding protein's N-terminal end, whereas mutations that alter the 3′ sequences of mRNA result in alterations in the protein's C-terminal end. What do these findings imply?
A. The N- and C-terminal ends of proteins are susceptible to alteration.
B. The genetic code is a series of amino acids (the component parts of proteins).
C. The order of nucleotides from 5′ to 3′ in mRNA determines the order of amino acids from N- to C-termini.
D. The genetic code is universal. - CORRECT ANSWER C
Which of the following types of RNA in eukaryotic cells come(s) from precursors that are subject to RNA processing?
A. rRNA, tRNA, and mRNA
B. rRNA and tRNA
C. tRNA and mRNA
D. mRNA - CORRECT ANSWER A
Which of the following is essential to the mechanism for terminating transcription in prokaryotes?
A. The polyadenylation signal sequence (AAUAAA)
B. Cleavage of the 3' end of the mRNA
C. Weaker H-bonding of A-U interactions compared to G-C interactions
D. A termination factor protein - CORRECT ANSWER C
Aminoacyl tRNA Synthetase attaches amino acids to tRNAs using an ester bond. That means the attachment is made in which of these ways?
A. amino group of amino acid to 5' end of tRNA
B. amino group of amino acid to 3' end of tRNA
C. carboxyl group of amino acid to 5' end of tRNA
D. carboxyl group of amino acid to 3' end of tRNA - CORRECT ANSWER D
Where wobble occurs at the third nucleotide of a codon, what trend to you notice?
A. purines are more flexible than pyrimidines
B. pyrimidines are more flexible than purines
C. wobble seems to be regulated by the size of the nucleotides in a pair
D. wobble seems entirely random - CORRECT ANSWER C
How many high-energy phosphoanhydride bonds are broken in the incorporation of a single nucleotide in DNA or RNA polymerization?
A. 0
B. 1
C. 2
D. 3
E. 4 - CORRECT ANSWER C
Common chaperones are identified as Hspwhich stands for heat shock protein. Why do you think these chaperones are identified this way?
A. they generate heat when they hydrolyze ATP
B. their production increases when a cell is exposed to heat
C. among proteins, they are specifically susceptible to degradation by heat
D. they transfer heat energy to other proteins - CORRECT ANSWER B
Which amino acid is responsible for the formation of disulfide bonds?
A. alanine
B. cysteine
C. glutamate
D. valine
E. aspartate - CORRECT ANSWER B
Resting potential in a mammalian neuron is ~ -70mV. What effect would opening sodium channels have on the membrane potential?
A. Depolarization
B. Hyperpolarization
C. No effect - CORRECT ANSWER A
What is the function of the inactivating particle of a voltage-gated sodium channel?
A. to prevent a nerve impulse from traveling in two directions instead of in just one
B. to increase the voltage amount needed to reach an action potential
C. to require new protein synthesis to replace used sodium channels and thus prevent neurons from firing too much
D. to provide a mechanism for potassium and sodium channels to create the right resting membrane potential - CORRECT ANSWER A
Voltage-gated Ca2+ channels at synaptic terminals open in response to an action potential reaching the end of an axon. Which of the following is responsible to the opening of these Ca2+ channels?
A. Depolarization from influx of Na+
B. Depolarization from influx of K+
C. Hyperpolarization from efflux of Na+
D. Hyperpolarization from efflux of K+ - CORRECT ANSWER A
Consider the ionotropic receptors. If activation of this reception is inhibitory, what sort of ion channel is the receptor?
A. Na+
B. K+
C. Ca2+
C. Cl- - CORRECT ANSWER B
Overall, what is the point of chemical signal transduction?
A. to internalize proteins that can then be degraded in the lysosomes
B. to sense and respond to the environment outside the cell
C. to control a cell's metabolism
D. to regulate cell motility - CORRECT ANSWER B
The G proteins we will focus on each have multiple subunits. Each has separate α, β, and γ subunits. How would we describe this protein quaternary structure?
A. Fibrous
B. Monomeric
C. Polarized
D. Hydrophobic
E. Trimeric - CORRECT ANSWER E
When activated, protein kinase A (PKA) phosphorylates target proteins. How is the specificity of proteins targeted achieved?
A. The longer that PKA's regulatory subunits are dissociated from the catalytic domain, the more different proteins the PKA phosphorylates.
B. The PKA is confined to specific membrane-bound organelles, where certain target proteins are also confined.
C. PKA's regulatory domains bind to the targets and facilitate the catalytic domains binding to the targets.
D. PKA's catalytic domains have active sites that can bind only to specific target proteins that have complementary shape and chemistry. - CORRECT ANSWER D
DNA is different from RNA in that
A. RNA is made up of five bases, whereas DNA is made up of four.
B. RNA contains an additional oxygen atom on the ribose sugar
C. In general, RNA molecules are longer than DNA molecules
D. RNA cannot exist as a double helix - CORRECT ANSWER B
Which of the following molecules can be considered a final product in the flow of genetic information within a cell?
A. protein
B. lipid
C. protein or RNA can be the final product of a gene
D. DNA
E. RNA - CORRECT ANSWER C
You are attempting to determine which step of prokaryotic translation a new antibiotic inhibits. You have determined that the antibiotic interacts with a translational factor but needs to identify with one. If the new antibiotic interferes with elongation, which of the following functions could the antibiotic disrupt?
A. IF3 interaction with an aminoacyl tRNA
B. EF-Tu interaction with GTP
C. EF-G interaction with an aminoacyl tRNA
D. EF-Tu interaction with the ribosomal P site - CORRECT ANSWER B
The C-terminal tail of RNA Polymerase II has multiple functions during transcription. What aspect of the C-terminal tail is responsible for determining the different functions?
A. length of the tail
B. secondary structure of the tail
C. methylation of the tail
D. phosphorylation state of the tail
E. splicing of the tail - CORRECT ANSWER D
Signaling in neurons is similar to signaling in other cells in many ways, but it is also unique. Which of the following is the most basic reason why signaling in neurons differs from signaling in other cells?
A. neurons do not use Ca2+ ions in signaling
B. neurons are the only cells that use ion channels in signaling
C. there is no signal transduction in neurons
D. signals through neurons must travel a longer distance
E. neurons do not use G proteins coupled receptors - CORRECT ANSWER D
In eukaryotes, the 3' end of the mRNA is important in the initiation of translation because
A. it contains Kozak sequences that aid in initiation
B. translation occurs in the 3' to 5' direction
C. the 3' poly(A) tail and PABP bind initiation factor eIF4G, stabilizing the 5' end of the mRNA
D. it contains Kozak sequences that aid in initiation of translation in the 3' to 5' direction
E. eIF4A is attached to the 3' end and removes any secondary structure that might prevent translation - CORRECT ANSWER C
Inosine is found
A. in rRNA
B. in some eukaryotic elongation factors
C. in the third position of some anticodons
D. in aminoacyl-tRNA synthetases
E. in the third position of some codons - CORRECT ANSWER C
Activation of a heterotrimeric G protein involves all of the following except
A. phosphorylation of GDP
B. dissociation of G-alpha from the G-beta-gamma subunits
C. removal of GDP
D. activation of a GPCR - CORRECT ANSWER A
Voltage-gated Ca2+ channels at synaptic terminals open in response to an action potential reaching the end of the axon. Which of the following is responsible to the opening of these Ca2+ channels?
A. depolarization from influx of Na+
B. depolarization from influx of K+
C. hyperpolarization from efflux of K+
D. hyperpolarization from efflux of Na+ - CORRECT ANSWER A
Suppressor tRNAs, Nonsense-mediated decay, and Nonstop decay are all mechanisms a eukaryotic cell may use to reduce the impact of specific types of mutations. Explain how each works. - CORRECT ANSWER 1. Suppressor tRNAs: recognize codons and replace them for functional amino acid coding codons (could be a potential problem if they remove the real stop codon).
2. Nonsense-mediated decay: during RNA processing, the intron segments are removed by spliceosomes and eons are joined together by protein complexes, EJC. In normal translation, the ribosome will bump off the EJC but in a nonsense mutation the ribosome will stop early and if it fails to bump off an EJC, enzymes will recognize them and target the mRNA for degradation.
3. Nonstop decay: when a nonstop mutation occurs (stop codon removed), the ribosome will keep moving down the sequence past where it should stop and will eventually end up dangling from the 3' end so enzymes will recognize this and target that mRNA for degradation.
Describe the similarities and differences between prokaryotic and eukaryotic promoter sequences. - CORRECT ANSWER Similarities:
- both use RNA Polymerase
- both follow the same basic process of initiation, elongation, termination
Differences:
- eukaryotes have 3 types of RNA polymerase but prokaryotes only have 1
- eukaryotic transcription and translation happen separate while prokaryotes can do it simultaneously
- prokaryotic termination uses a hairpin loop while eukaryotic termination uses DNA cleavage
You have isolated a piece of DNA that you believe contains an interesting gene. Using a mix of RNA polymerase and ribonucleotides, you perform in vitro transcription. However, even though all of your controls work, no mRNA is created from your DNA fragment. Working backward, you note that your DNA preparation removed approximately 250 base pairs from the upstream end of the gene. The most likely explanation is that during DNA preparation.
A. the RNA polymerase became inactivated
B. the promoter was removed
C. the termination signal was removed
D. the 5' methyl guanosine cap was removed - CORRECT ANSWER B [Show Less]