Homework Questions: Final Exam Flashcards by Emma Sellers

When secreted in the human body, the hormone glucagon causes rapid degeneration of glycogen in liver cells. This mobilization of glycogen is accomplished through a signaling pathway. What is the proper temporal sequence of the following steps in this reaction cascade?

A - displacement of GDP with GTPon the a-subunit of the G-proteins

B - phosphorylation of glycogen

C - dissociation of the regulatory subunits activates protein kinaseA

D - phosphorylation of glycogen phosphorylase

E - glucagons binds to a specific, transmembrane receptor

F - formation of cyclic-AMP by adenylyl cyclase

E-A-F-C-D-B

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Which of the following statements concerning receptors is CORRECT?

a) they have a ligand binding site on the extracellular side of the membrane
b) they have an active site on the extracellular side of the membrane
c) they contain an enzyme activity for which the signal molecule is a substrate
d) they bind signal molecules in a non-specific manner

a) they have a ligand binding site on the extracellular side of the membrane

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insulin binds to a receptor that ______.
I. is coupled to a G protein
II. possesses tyrosine kinase activity
III. possesses serine/threonine phosphatase activity
IV. interacts with proteins such as IRS-1

II, IV

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which of the following would diminish a hormone signal mediated via a G protein signal transduction system?

a) addition of a substance which inhibits adenylate cyclase
b) greater than normal expression of the receptor in the cell membrane
c) addition of a substance which inhibits the GTPase activity of the G protein
d) addition of a substance such as caffeine, which inhibits phosphodiesterase

a) addition of a substance which inhibits adenylate cyclase

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the second messenger ________ is produced by the enzyme __________.

a) nitric oxide; arginase
b) cGMP; GTP cyclase
c) cAMP; adenylate cyclase
d) triacylglycerol; phospholipase C
e) inositol diphosphate; phospholipase C

c) cAMP; adenylate cyclase

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the _______ receptor is a receptor kinase.

a) a1-adrenergic
b) B2-adrenergic
c) calmodulin
d) insulin
e) cortisol

d) insulin

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which one of the following statements about the glucagon signaling pathway is TRUE?

a) the G protein is a second messenger
b) activated adenylate cyclase decreases the concentration of cAMP
c) protein kinase A is the target protein (enzyme)
d) the glucagon receptor protein interacts with adenylate cyclase
e) the activity of protein kinase A is dependent on the concentration of cAMP

e) the activity of protein kinase A is dependent on the concentration of cAMP

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which of the following does NOT occur in biological signaling systems?

a) protein-protein interactions
b) ligand-protein interactions
c) opening or closing of ion channels
d) autophosphorylation
e) all of the above processes may occur

e) all of the above processes may occur

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In a G protein signal-transduction system, what role does the G protein play?

a) it activates a target protein (enzyme)
b) it produces the second messenger molecule
c) it reverses the activation of the receptor caused by ligand binding
d) it transmits the signal from the receptor to other components of the signaling system

d) it transmits the signal from the receptor to other components of the signaling system

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ligand binding to a receptor tyrosine kinase causes _______ of the receptor which then ________ the next protein in the signaling pathway.

a) methylation; hydrolyzes
b) hydrolysis; inhibits
c) phosphorylation; phosphorylates
d) acylation; activates
e) none of the above

c) phosphorylation; phosphorylates

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which of the following is a ligand of the B2-adrenergic receptor?

a) tyrosine
b) serotonin
c) norepinephrine
d) caffeine
e) adenosine

c) norepinephrine

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a small molecule produced inside a cell in response to a hormone binding to its receptor is called a(n) ___________.

a) inside messenger
b) agonist
c) antagonist
d) second messenger
e) G protein

d) second messenger

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what group is attached to the pyrimidine ring in thymine and is not present in uracil?
a) ribose
b) -CH3
c) -NH2
d) deoxyribose
e) none of the above

b) -CH3

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the coenzymes known as NAD+, FAD and coenzyme A all contain a derivative of ______.
a) uridine
b) thymidine
c) adenosine
d) guanosine
e) cytidine

c) adenosine

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nucleoside triphosphate are useful for energy transfer because the pisphoanhydride bonds are relatively ________.
a) stable
b) biocompatible
c) high energy
d) large
e) low energy

c) high energy

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which of the following is correctly paired with its nucleoside?

a) cytosine: cytidine diphosphate
b) adenine: adenylate
c) uridine: uridine triphosphate
d) guanine: guanosine
e) thymine: thymidylate

d) guanine: guanosine

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which of the following is TRUE about the about the oligonucleotide that is represented below?

AUCCGAUC

a) it has an A at its 3’ terminus
b) it is a DNA oligonucleotide
c) it contains 3 pyrimidine bases
d) it has a purine at its 5’ terminus

d) it has a purine at its 5’ terminus

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identify the purine nucleoside.

a) cytosine
b) guanosine
c) uridine
d) adenylic acid

b) guanosine

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the 5 end of a polynucleotide contains ______ while the 3’ end contains ______.

a) a hydroxyl group; a phosphate group
b) a phosphate group: a hydroxyl group
c) a phosphate group: a phosphate group
d) a hydroxyl group: a hydroxyl group
e) none of the above

b) a phosphate group: a hydroxyl group

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an A-T base pair consists of ________ H-bond(s); a C-G base pair consists of _______ H-bond(s)

a) 3;2
b) 2;3
c) 2;2
d) 1;2
e) 2;1

b) 2;3

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which of the following statements is TRUE regarding phosphodiester bonds that link adjacent nucleotides in both RNA and DNA?

a) phosphodiester bonds join the 3’ hydroxyl of one nucleotide to the hydroxyl of the next
b) phosphodiester bonds are unchanged at pH 7.0
c) phosphodiester bonds always link G with C and A with either T or U
d) phosphodiester bonds are positively charged

a) phosphodiester bonds join the 3’ hydroxyl of one nucleotide to the hydroxyl of the next

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Which of the following statements about the structure of the double-stranded DNA is FALSE?

a) some groups of the bases exposed in the grooves of double-stranded DNA
b) the phosphodiester backbone interacts with Mg2+ in the cell
c) DNA is stabilized primarily by H-bonding between the bases
d) only non-covalent forces stabilize the helix so that the DNA can unwind during replication and transcription

c) DNA is stabilized primarily by H-bonding between the bases

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which of the following statements is NOT true about base Watson-Crick complementary pairing:

a) each base is hydrogen bonded to a base in the opposite strand to form planar base pair
b) each A pairs with T and each G pairs with C
c) an A:T base pair is stronger that a G:C pair
d) each DNA strand can act as a template for the synthesis of its complementary strand

c) an A:T base pair is stronger that a G:C pair

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differences in structure between a DNA helix and an RNA helix can predominantly be attributed to the presence of _____ in RNA

a) uracil
b) 2’ hydroxyl group
c) 3’ hydroxyl group
d) smaller sizes of RNA molecules
e) none of the above

b) 2’ hydroxyl group

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the replication of DNA is made possible by the presence of ______ strands in the double helix of DNA a) antiparallel b) hydrogen bonded c) complementary d) genomic e) none of the above

c) complementary

DNA encodes proteins undergoes the process of ______ to produce _______. a) translation; proteins b) transcription; proteins c) transcription; tRNA d) transcription; mRNA e) translation; rRNA

d) transcription; mRNA

the DNA strand that serves as the template for the synthesis of RNA is often called the ________. a) transfer strand b) messenger strand c) coding strand d) noncoding strand e) transcription strand

d) noncoding strand

which of the following is most correct? a) DNA polymerase can only add pyrophosphate to the free 3'-OH group of a base paired polynucleotide b) DNA polymerase can only add a nucleotide to the free 5'-OH group of a base-paired polynucleotide c) DNA polymerase can only add a nucleotide to the free 3'-OH group of a polynucleotide that is not based-paired d) DNA polymerase can only add a nucleotide to the free 3'-OH group of a base-paired polynucleotide

d) DNA polymerase can only add a nucleotide to the free 3'-OH group of a base-paired polynucleotide

the DNA strand that serves as the template for the synthesis of RNA is often called the ________. a) transcription strand b) noncoding strand c) transfer strand d) messenger strand e) coding strand

b) noncoding strand

which of the following statements about proofreading in DNA polymerases is TRUE? a) proofreading occurs in all DNA polymerases b) proofreading enhances the processivity of DNA polymerases c) proofreading occurs in the same active site as polymerization d) proofreading is, specifically, a 3' endonuclease activity e) proofreading is a hydrolysis

e) proofreading is a hydrolysis

what metal cations are found in the active site of DNA polymerase? a) two Zn2+ b) one Zn2+ and one Mg2+ c) two Mg2+ d) one Mg2+ and one Ca2+ e) two Ca2+

c) two Mg2+

E. coli primary begins polymerizing nucleotides at a 5'-CTG-3' sequence in DNA. What are the first three bases in the resulting primer? a) the primase synthesizes a 5'-GCA-3' RNA chain b) the primase synthesizes a 5'-GAC-3' RNA chain c) the primase synthesizes a 5'-CAG-3' RNA chain d) the primase synthesizes a 5'-ACG-3' RNA chain

c) the primase synthesizes a 5'-CAG-3' RNA chain

read the following statements carefully and determine which are true and which are false. 1. single-stranded nucleic acids such as RNA can from complex, 3-D, folded structures 2. RNA does not contain uracil 3. translation is carried out by an enzyme called RNA polymerase

1 is true , and 2 & 3 are false

If one strand of a double-stranded DNA helix has the sequence 5'-ACGTAACC-3', which of the following accurately denotes the sequence of the complementary region of the other strand? a) GGTTACGT b) TGCATTGG c) ACGTAACC d) CCAATGCA

a) GGTTACGT

which strand of DNA is replicated exclusively in a discontinuous fashion? a) forward strand b) reverse strand c) leading strand d) lagging strand e) the strand that is read in the 5' to 3' direction

d) lagging strand

during DNA replication the polymerase accidentally inserts an A opposite a C in the template strand. what type of mutation(s) could this cause in the DNA? a) nonsense mutation b) missence mutation c) frame-shift mutation d) either A or B

d) either A or B

which of the following is FLASE regarding plasmids found in bacterial cells? a) they are small, circular molecules of single stranded DNA b) they are part of the cell's genome c) they may confer antibiotic resistance on the cell d) they may make the cell more virulent

a) they are small, circular molecules of single stranded DNA

In eukaryotic DNA, 5-methylcytosine (5-mC) may be found in place of cytosine in the DNA double helix. Which of the following is 5-mC?

the molecule in the middle

what effect does a topoisomerase have upon DNA? a) denatures DNA b) converts double stranded DNA to single stranded DNA c) changed the supercoiling of DNA d) changes B-form DNA to A-form e) none of the above

c) changed the supercoiling of DNA

what does this image show? a) chromatin b) a histone c) a DNA double helix d) a complex of histones e) a nucleosome

e) a nucleosome

The protein that is responsible for bringing together proteins bound to enhancers with proteins bound to promoters is called __________. a) TAF1 b) chromatin remodeling enhancer c) mediator complex d) subunit of RNA polymerase e) none of the above

c) mediator complex

read the following three statements carefully and determine which are true and which are false. i) nucleic acids are synthesized in the 3'-5' direction ii) the sugar-phosphate groups which for the "backbone" of the DNA double-helix are located on the outside of the helix because they are polar iii) RNA polymerase "reads" a template strand by running along it in a 5'-3' direction

i) & iii) are false, and ii) is true

what sugar is metabolized by the enzymes under the control of the lac operon? a) sucrose b) mannose c) galactose d) lactose e) maltose

d) lactose

which of the following best describes the DNA binding properties of the TATA-binding protein? a) TBP unwinds duplex DNA at the TATA box, forming a transcription bubble b) TBP encircles duplex DNA at the TATA box c) TBP sharply kinks duplex DNA at the TATA box, in part by inserting Phe residues into the base-pairing regions d) TBP binds to duplex DNA with high affinity somewhere near the site where transcription starts

c) TBP sharply kinks duplex DNA at the TATA box, in part by inserting Phe residues into the base-pairing regions

read the following statements carefully and determine which are true and which are false. i) single-stranded nucleic acids such as RNA can form complex, 3-D, folded structures ii) RNA does not contain uracil iii) translation is carried out by an enzyme called RNA polymerase

i) is tru, and ii) & iii) are false

All cellular RNAs are transcribed from ________. a) DNA templates b) RNA templates c) either DNA or RNA templates, but not in the same organism d) a combination of DNA and RNA templates e) none of the above

a) DNA templates

separation of DNA into a single stranded region around RNA polymerase creates ________. a) hybridized DNA b) a transcription bubble c) Z-DNA d) DNA bound to single stranded binding proteins e) none of the above

b) a transcription bubble

radioactively labeled y-[32P]GTP is added to a bacterial culture undergoing transcription. Is the resulting RNA labeled? If so, where? a) the 5' end of any prokaryotic RNAs ending in C will be labeled b) the 5' end of any prokaryotic RNAs ending in G will be labeled c) the 3' end of any prokaryotic RNAs ending in C will be labeled d) the 3' end of any prokaryotic RNAs ending in G will be labeled

b) the 5' end of any prokaryotic RNAs ending in G will be labeled

what are the two metal ions found in the active site of RNA polymerase? a) two Ca2+ b) a Ca2+ and a Zn2+ c) two Zn2+ d) a Zn2+ and a Mg2+ e) two Mg2+

e) two Mg2+

RNA synthesis in a test tube would require RNA polymerase plus a) an RNA template, an RNA primer, and NTPs b) a DNA template, an RNA primer, and dNTPs c) an RNA template and dNTPs d) a DNA template and NTPs

d) a DNA template and NTPs

How do the NTPs enter RNA polymerase? a) base-paired with the incoming (downstream) DNA b) with the incoming DNA but not base-paired with it c) from the exit site, as the DNA leaves the enzymes, the NTPs move in the opposite direction d) through a special channel sized just for NTPs e) there is no specific way, any of the above routes are used

d) through a special channel sized just for NTPs

the C-terminal domain of eukaryotic RNA polymerase a) undergoes phosphorylation b) helps unwind the DNA helix c) dissociates during the elongation phase d) acts as a primer for RNA synthesis

a) undergoes phosphorylation

phosphorylation of the C-terminal domain of eukaryotic RNA polymerase inhibits interaction with what protein, thus allowing the polymerase to leave the promoter? a) mediator complex b) all transcription factors c) TFIIF and TFIIH d) TFIIS e) none of the above

a) mediator complex

why is it tolerable that the error frequency in RNA synthesis is 10^4 - 10^6 times higher than that for DNA synthesis?

because most genes are transcribed many times, but not all nucleotide substitutions will lead to amino acid substitutions, and amino acid substitutions in proteins are often functionally innocuous

in a typical gene, what percentage of the bases represents introns? a) 5% b) 10% c) 25% d) 50% e) 90%

e) 90%

Which of the following statements about the genetic code is FALSE? a) AUG encodes methionine and is also the start signal for translation b) codons in mRNA are "read" by base pairing with anticodons in tRNA c) serine is only represented by four codons, UCU, UCC, UCA, and UCG d) the genetic code is described as degenerate because there are more codons than amino acids

c) serine is only represented by four codons, UCU, UCC, UCA, and UCG

the genetic code is said to be ________ because several codons may correspond to the same amino acid. a) depraved b) degenerate c) deteriorate d) despicable e) decadent

b) degenerate

Transfer RNA molecules are involved in ________. a) reverse transcription b) replication c) transcription d) post-translation processing e) translation

e) translation

which of the following is required for the correct charging of a tRNA? a) tRNA, amnio acid, GTP and transpeptidase b) tRNA, amino acid, ATP and transpeptidase c) tRNA, mRNA, amino acid, ATP and transpeptidase d) tRNA, mRNA, amino acid, GTP and aminoacyl-tRNA synthetase e) tRNA, amino acid, ATP and aminoacyl-tRNA synthetase

e) tRNA, amino acid, ATP and aminoacyl-tRNA synthetase

during the charging of a tRNA, what intermediate is formed? a) tRNA-adenylate b) aminoacyl-ADP c) aminoacyl-tRNA d) none of the above e) aminoacyl-adenylate

e) aminoacyl-adenylate

what is the minimum number of mutations that can convert a codon for Ile into a codon for Ser? a) 1 b) 2 c) 3

a) 1

which of the following tRNA binding sites is correctly defined? a) A site: accepts incoming aminoacyl-tRNA b) E site: entrance site for initial tRNA binding c) P site: site occupied by the tRNA that accepts the growing peptide chain d) T site: site that is briefly occupied while the tRNA is passed from the A site to P site e) all of the above

a) A site: accepts incoming aminoacyl-tRNA

approximately what fraction of the mass of a ribosome is due to protein? a) 1/6 b) 1/5 c) 1/3 d) 1/2 e) 1/4

c) 1/3

what are the predominant interactions between the 30S and 50S subunits that allow the formation of the 70S ribosome? a) interactions of 50S rRNA with tRNA D loop interactions of 30S rRNA with anticodon loop are the only interactions holding the 70S ribosome together b) rRNA-rRNA interactions from both subunits c) 30S rRNA with 50S protein d) 30S protein with 50S rRNA e) protein-protein interactions from both subunits

b) rRNA-rRNA interactions from both subunits

in the translocation step of translation, EF-G is able to bind in the A site on the ribosome because of its structural similarity to which of the following? a) tRNA b) EF-Tu-tRNA c) EF-Tu d) EF-Ts

b) EF-Tu-tRNA

which of the following antibiotics mimics an aminoacyl-tRNA? a) puromycin b) penicillin c) erythromycin d) streptomycin e) chloramphenicol

a) puromycin

which of the following initiation factors is a G protein? a) IF-3 b) IF-I c) eIF-4F d) IF-2

d) IF-2

the bacterial elongation factors EF-Tu and EF-G are essential for translation in vivo, but bacterial ribosomes can translate mRNA into protein in vitro in the absence of EF-Tu and EF-G. How does their absence affect the accuracy of translation? a) their absence decreases accuracy of translation b) their absence increases accuracy of translation c) their absence does not affect translation

a) their absence decreases accuracy of translation

what recognizes stop codons? a) nothing recognizes stop codons, that is why translation ceases b) ribosome recycling factors c) fMet-tRNA d) a termination of tRNA that does not carry an amino acid on its acceptor stem e) release factors

e) release factors

polypeptide synthesis proceeds from the _______ to the ______. a) 50S subunit; 30S subunit b) C-terminus; N-terminus c) peptidyl site; aminoacyl site d) entrance site; exit site e) N-terminus; C-terminus

e) N-terminus; C-terminus

DNA polymerase from Thermus aquatics is used in PCR because _________. a) the enzyme is readily deactivated by heat, effectively halting the reaction b) it is stable at high temperatures c) the genes from Thermus aquatics are readily distinguished from those of "normal" organisms d) it is not infectious e) it is a soluble protein

b) it is stable at high temperatures

which is more likely to be called a "rare cutter": a restriction enzyme with a four-base recognition sequence or a restriction with an eight-base recognition sequence? a) a restriction enzyme with a four-base recognition sequence b) a restriction enzyme with an eight-base recognition sequence

b) a restriction enzyme with an eight-base recognition sequence

because of the high temperature _______ step during a PCR reaction, the DNA polymerase from _______ is used. a) primer extension; bacteriophage b) primer annealing; thermos aquaticus c) primer extension; E. coli d) strand separation; Thermus aquaticus e) strand separation; E. coli

d) strand separation; Thermus aquaticus

mutations leading to changes that can be inherited by the next generation have to be introduced at the ________ level a) mRNA b) protein c) DNA d) rRNA e) tRNA

c) DNA

what enzyme is required to form a new phosphodiester bond when inserting DNA into a plasmid? a) ligase b) endonuclease c) exonuclease d) DNA polymerase e) clonase

a) ligase

a researcher trying to identify the gene for a known protein might begin by looking closely at the protein's sequence in order to design a single-stranded oligonucleotide probe that will hybridize with the DNA of the gene. Why would the researcher focus on a segment of the protein containing a methionine (Met) or tryptophan (Trp) residue? a) methionine and tryptophan are each encoded by a single codon b) methionine and tryptophan are average in amino acid molecular weight c) RNA polymerase most easily recognizes Met and Top d) none of the above

a) methionine and tryptophan are each encoded by a single codon

what term described the production of multiple identical organisms from a single ancestor? a) phenotyping b) transcription c) cloning d) sequencing e) ligation

c) cloning