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Cell Molec > EXAM 1 & 2 > Flashcards

EXAM 1 & 2 Flashcards

1
Q 
Which of the following proteins is involved in the process of translation?
A) topoisomerase
B) RNA polymerase
C) Aminoacyl-tRNA synthetase
D) Ligase
E) Ribosomal RNA
A

Aminoacyl-tRNA synthetase

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2
Q 
A nucleotide can vary in:
A) the base
B) the sugar
C) the phosphate group
D) the base and the phosphate group
E) the sugar and the base
A

the sugar and the base

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3
Q 
The first stage of protein translation occurs when tRNA-Met base pairs with the mRNA being translated in the ribosomal:
A) P site
B) A site
C) E site
D) T site
E) R site
A

P site

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4
Q

A protein containing several Proline residues is:
A) Not likely to form quaternary structures
B) Not likely to form alpha helices
C) Likely to be found in beta turns
D) Likely to form alpha helices
E) Likely to be an integral membrane protein

A

Not likely to form alpha helices

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5
Q 
Which of the following recognizes the UAG, UAA, and UGA codons?
A) release factors
B) elongation factors
C) various tRNAs
D) RNA polymerase
E) DNA polymerase
A

release factors

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6
Q 
When a protein is targeted for destruction by the proteasome, it must be ubiquitinylated. A ubiquitin is added to what in the target protein?
A) Proline residue
B) Leucine reside
C) Arginine residue
D) Glycine residue
E) Lysine residue
A

Lysine residue

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7
Q 
A double-stranded breakage repair pathway that requires the presence of a second chromosome carrying the same sequence of genes as the damaged chromosome is:
A) NHEJ
B) DNA methylation repair
C) Nonhomologous end joining repair
D) Homologous recombination
E) Nonhomologous recombination
A

Homologous recombination

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8
Q

The 3’ end of most eukaryotic mRNAs contains a _____, while the 5’ end has a _____.
A) Poly(U) tail, methylated guanosine cap
B) Poly(A) tail, sulfonated guanosine cap
C) Poly(A) tail, methylated guanosine cap
D) Methylated guanosine cap, Poly(A) tail
E) Methylated guanosine cap, Poly(U) tail

A

Poly(A) tail, methylated guanosine cap

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9
Q 
Which of the following is a mechanism for regulating protein activity?
A) ligand binding
B) phosporylation
C) dephosphorylation
D) proteolytic processing 
E) All of the above
A

all of the above

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10
Q

GTPases serve in many signal transduction pathways and the presence of GTP or GDP indicates whether the pathway is on or off, respectively. Which of the following statements is true regarding guanine nucleotide exchange factors (GEF) and their role in these signaling pathways?
A) They catalyze the dissociation of GDP on the G-protein to therefore promote the replacement of GTP
B) They hydrolyze GTP into GDP and Pi
C) They decrease the GTPase activity of the G-protein
D) None of the above
E) All of the above

A

They catalyze the dissociation of GDP on the G-protein to therefore promote the replacement of GTP

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11
Q 
Which enzyme gives the ubiquitin-proteasome system specificity as to which protein gets targeted from degradation?
A) E1
B) Ubiquitin
C) E2
D) E3
E) DUB
A

E3

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12
Q 
What type of protein secondary structure is characterized as being highly extensible because of its coiled structure?
A) supercoiling
B) beta turns
C) beta sheets 
D) double helix
E) alpha helix
A

alpha helix

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13
Q

Which of the following is defined as the tertiary structure of a protein?
A) the primary amino acid sequence
B) structural features such as a turn
C) structural domains such as DNA binding domain
D) folded structures such as an alpha helix
E) none of the above

A

structural domains such as DNA binding domain

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14
Q 
Phospholipids assemble in bilayers because they are:
A) water-loving
B) amphipathic
C) phospholipid derivatives
D) water-hating
E) steroid-derivatives
A

amphipathic

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15
Q 
What kind of membrane protein is found entirely outside the bilayer on either the extracellular or cytoplasmic surface and linked to a membrane lipid situated within the bilayer?
A) galactocerebroside
B) lipid-anchored protein
C) integral protein
D) peripheral proteins
E) phosphatidylcholine
A

lipid-anchored protein

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16
Q

All of the following steps are performed by the enzyme transposase during transposition of bacterial insertion sequences exept:
A) synthesis of DNA to fill in the single-stranded gaps
B) introduction of blunt-ened cuts into the donor DNA
C) ligation of the IS element to the target DNA
D) excision of the IS element from the door DNA molecule
E) introduction of staggered cuts into the target DNA molecule

A

synthesis of DNA to fill in the single-stranded gaps

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17
Q 
Changes in the conformational shape of an enzyme that diminish the size of its ligand-binding pocket are likely to affect an enzyme's:
A) epitope
B) affinity
C) specificity
D) specificity and affinity
E) epitope and affinity
A

specificity and affinity

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18
Q 
Kinases, which are responsible for the activation or inactivation of a number of proteins, can add phosphate groups onto:
A) tryptophan residues
B) cysteine residues
C) serine residues
D) tryptophan and serine residues
E) cysteine and tryptophan residues
A

serine residues

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19
Q 
Histone modifications play integral roles in chromatin condensation and function. Which of the following is NOT considered to be a histone modification?
A) ubiquitinylation
B) phosphorylation
C) prenylation
D) acetylation
E) methylation
A

prenylation

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20
Q

All the following statements about molecular chaperones are true EXCEPT:
A) they are found only in mammals
B) they sequester the polypeptide from other components of the cytoplasm
C) they bind a wide range of proteins
D) they are located in every cellular compartment
E) they play a role in the proper folding of proteins

A

they are found only in mammals

21
Q 
Which amino acid is capable of forming a disulfide bond?
A) cytosine
B) cysteine
C) asparagine
D) glutamine
E) methionine
A

cysteine

22
Q

You disrupt all of the hydrogen bonds in a protein. What level of structure will be preserved?
A) primary structure
B) secondary structure
C) tertiary structure
D) quaternary structure
E) no level of protein structure will be preserved

A

primary structure

23
Q 
In which of these polymers are the monomers added one at a time?
A) DNA
B) mRNA
C) protein
D) none of the above
E) all of the above
A

all of the above

24
Q 
An enzyme that breaks DNA, dispels the tension, and reseals the strand ahead of the DNA replication fork is called a:
A) helicase
B) topoisomerase 
C) DNA polymerase
D) phosphodiesterase 
E) ligase
A

topoisomerase

25
Q

Place the events below in the correct order:
1 - G protein binds to activated receptor forming a receptor-G protein complex
2 - release of GDP by the G protein
3 - binding of GTP by the G protein
4 - binding of a hormone or neurotransmitter to a G protein-coupled receptor
5 - conformational shift I the alpha subunit of the G protein
A) 4-1-2-5-3
B) 3-4-1-5-2
C) 4-1-5-3-2
D) 4-5-1-2-3
E) 4-1-3-5-2

A

4-1-2-5-3

26
Q

What happens to membrane proteins that have been attached to a single ubiquitin molecule?
A) they stay in the membrane
B) they are selectively incorporated into endocytic vesicles
C) they move immediately to proteasomes
D) they move directly to the smooth endoplasmic reticulum
E) they move to the rough endoplasmic reticulum

A

they are selectively incorporated into endocytic vesicles

27
Q

Where are v-SNARES and t-SNARES found, respectively?
A) incorporated into transport vesicle membranes during fusion; in target compartment membranes
B) in target compartment membranes; incorporated into transport vesicle membranes during fusion
C) in target compartment membranes; incorporated into transport vesicle membranes during budding
D) incorporated into transport vesicle membranes during budding; in target compartment membranes
E) in target compartment membranes; in target compartment membranes

A

incorporated into transport vesicle membranes during budding; in target compartment membranes

28
Q

Amino acid entry into cells can occur via uniporters or symporters. If the rate of leucine entry into the cells increases when the pH decreases, what does this suggest?
A) Leu is crossing the membrane via simple diffusion
B) Leu is being transported by a uniporter
C) Leu is being transported by a H+ symporter
D) Leu is being transported through a Cl- channel
E) Leu is being actively pumped across the membrane against its concentration gradient

A

Leu is being transported by a H+ symporter

29
Q

What does Sar1 bind after it binds to GTP?
A) the cytosolic side of the plasma
B) the cytosolic side of the ER membrane
C) the cytosolic side of the Golgi membrane
D) the luminal side of the Golgi membrane
E) the luminal side of the ER membrane

A

the cytosolic side of the ER membrane

30
Q 
Which molecule below is a GTP-binding protein that is required for the release of a clathrin-coated vesicle from the membrane on which it was formed?
A) GGA
B) Opsonin
C) Clathrin
D) Dynamin
E) AP2
A

Dynamin

31
Q

What kinds of responses are NOT initiated when signals traveling down signaling pathways reach their target proteins?
A) a change in ion permeability
B) cessation of DNA synthesis and degradation of DNA
C) a change in gene expression
D) an alteration of the activity of metabolic enzymes
E) the death of the cell

A

cessation of DNA synthesis and degradation of DNA

32
Q 
Proteins destined for the inner mitochondrial membrane or the mitochondrial matrix must pass through the:
A) TIM complex
B) TOM complex
C) intermembrane space
D) at least one protein channel
E) all of the above
A

all of the above

33
Q

What phenotype would be observed in a cell containing a non-hydrolysable form of GTO with respect to the vesicles of the secretory pathway?
A) coated vesicles would accumulate
B) uncoated vesicles would accumulate
C) secretion of peptide from the cell would be increased
D) vesicles would be delivered to incorrect target membranes
E) all of the above

A

coated vesicles would accumulate

34
Q

How do protein coats select the cargo molecules to be carried by the vesicles they help to form?
A) the coat proteins attach to the extracellular matrix
B) the coat proteins directly attach to the cargo proteins in the lumen of the forming vesicles
C) the coats contain a targeting signal located at the luminal tails of proteins that interacts with the cargo proteins
D) the protein coats have a specific affinity for the sorting signal located at the cytosolic tails of cargo proteins
E) they electromagnetically attract the correct cargo proteins

A

the protein coats have a specific affinity for the sorting signal located at the cytosolic tails of cargo proteins

35
Q 
When present, the TAT, CAAT, and GC boxes are typically found within 100-150 base pairs upstream from the transcription start site. Due to their closeness to the start gene, they are often called:
A) primary promoter sites
B) proximal promoter elements
C) primary promoter elements
D) distal promoter elements
E) central promoter sites
A

proximal promoter elements

36
Q 
Muscarinic acetylcholine receptors are GCPRs that slow the rate of heart muscle contraction upon ligand binding/activation. Activation of this receptor leads to opening of potassium channels triggered by decreases in cAMP levels. The muscarinic acetylcholine receptor likely couples to:
A) Gai
B) Gas
C) Gao
D) Gat
E) Gaq
A

Gai

37
Q

The binding of a hormone to a receptor tyrosine kinase (RTK) causes all of the following except:
A) dimerization of the receptor
B) hydrolysis of GTP bound to Ras
C) autophosphorylation of the receptor
D) activation of Ras through an interaction with GRB2 and Sos
E) all of the above result from the binding of a hormone to a RTK

A

hydrolysis of GTP bound to Ras

38
Q

How is RISC directed to the target mRNA that it is destined to destroy?
A) the siRNA is magnetically attracted to the target mRNA
B) the siRNA is complementary to the slicer ribonuclease
C) the single-stranded siRNA is complementary to the target mRNA and directs the RISC to it
D) the passenger strand acts like a guide to direct the RISC to the target
E) the ribonuclease slicer directs RISC to the cleavage site

A

the single-stranded siRNA is complementary to the target mRNA and directs the RISC to it

39
Q 
What process is responsible for the organelle turnover in the cell and carries out the regulated destruction of the cell's own organelles for the purpose of recycling the components of which they are made?
A) autophagy
B) autonomy
C) apoptosis 
D) autolysis 
E) autophagolysosome
A

autophagy

40
Q

What would happen if the enzyme that adds phosphate groups to the appropriate mannose residues on the carbohydrate chains of lysosomal enzymes were defective?
A) lysosomes would be degraded
B) lysosomal enzymes would continue through the Golgi complex to secretory vesicles and would be constitutively secreted
C) lysosomal enzymes would be localized to peroxisomes
D) lysosomal enzymes would be localized to lysosomes
E) lysosomal enzymes would be degraded

A

lysosomal enzymes would continue through the Golgi complex to secretory vesicles and would be constitutively secreted

41
Q

Which of the following is NOT true about the role of adapter proteins in the activation of Ras by receptor tyrosine kinases?
A) GRB2 interacts with the receptor via SH2 domain
B) Sos acts as a GAP which helps convert RasGDP to activate RasGTP
C) GRB2 and Sos proteins couple the receptor to the inactive RasGDP complex
D) following dimerization and autophosphorylation of receptor tyrosine kinases, GRB2 and Sos proteins couple to the receptor
E) GRB2 interacts with Sos via its Sh3 domain

A

Sos acts as a GAP which helps convert RasGDP to activate RasGTP

42
Q 
What is responsible for synthesizing hnRNAs?
A) general transcription factors
B) reverse transcriptase
C) RNA polymerase I
D) RNA polymerase II
E) RNA polymerase III
A

RNA polymerase II

43
Q 
Which of the following events occur during epinephrine-stimulated glycogen metabolism?
A) activation of PKA by cAMP
B) decreased glycogen synthesis 
C) increased cAMP
D) inactivation of protein phosphatases 
E) all of the above
A

all of the above

44
Q

Which of the following small GTPases are NOT involved in vesicle budding or docking?
A) ARF
B) Ras
C) Rab
D) Sar
E) all of these are GTPases involved in vesicle budding or docking

A

Ras

45
Q

You are studying the effects of a-amanitin, a poisonous cyclic octapeptide, on eukaryotic cells and have noticed that following treatment, there is no miRNA transcription. Based on this evidence you conclude that a-amanitin must be inhibiting:
A) DNA polymerase
B) RNA polymerase I and RNA polymerase II
C) RNA polymerase I
D) RNA polymerase II
E) RNA polymerase III

A

RNA polymerase II

46
Q

How are integral membrane proteins thought to enter the lipid bilayer?
A) it is thought that they are enzymatically implanted in the lipid bilayer
B) it is thought that they burrow into the lipid bilayer
C) they insert into the membrane from the cytosol after their synthesis is complete
D) the translocon channel gives each nascent polypeptide segment a chance to partition itself into the lipid bilayer’s hydrophobic core
E) they instert into the membrane from the RER lumen after their synthesis is complete

A

the translocon channel gives each nascent polypeptide segment a chance to partition itself into the lipid bilayer’s hydrophobic core

47
Q 
Which amino acids are known to be phosphorylated by protein kinases?
A) serine, leucine, tyrosine
B) phenylalanine, serine, tyrosine
C) tyrosine, threonine, glycine
D) serine, threonine, tyrosine
E) threonine, serine, tryptophan
A

serine, threonine, tyrosine

48
Q

When the regulatory domain of a protein kinase A (PKA) is bound to cAMP:
A) the regulatory subunit travels to the nucleus
B) the AKAP adaptor protein sequesters the catalytic subunit
C) the catalytic subunit acts on CRE to stimulate gene transcription
D) the released catalytic subunit travels to the nucleus where it phosphorylates CREB
E) PDE is inhibited to cause cAMP levels to rise

A

the released catalytic subunit travels to the nucleus where it phosphorylates CREB

49
Q 
In the absence of targeting information, what is the default location of proteins synthesized on cytosolic ribosomes?
A) the nucleus
B) the cytoplasm
C) the rough ER
D) the plasma membrane
E) the Golgi complex
A

the cytoplasm

Cell Molec (16 decks)

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