Cell Biology Exam 2

Consider two genes that are next to each other on a chromosome, as arranged in the figure Q5Q9.pdfPreview the document Which of the following statements is true? A) Gene A and gene B can be transcribed at different rates, producing different amounts of RNA within the same cell. B) The two genes must be transcribed into RNA using the same strand of DNA. C) If gene A is transcribed in a cell, gene B must be transcribed. D) If gene A is transcribed in a cell, gene B cannot be transcribed.

A) Gene A and gene B can be transcribed at different rates, producing different amounts of RNA within the same cell.

Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus? A) The ribosome binds to the mRNA. B) RNA polymerase dissociates. C) The mRNA is polyadenylated at its 3' end. D) 7-methylguanosine is added in a 5'-to-5' linkage to the mRNA.

A) The ribosome binds to the mRNA.

Cholesterol serves several essential functions in mammalian cells. Which of the following is not influenced by cholesterol? A) membrane thickness B) membrane fluidity C) membrane permeability D) membrane rigidity

A) membrane thickness

In the diagram it shows you two neurons that are in tandem in the brain (one right next to the other). When these cells need to have one turn on the next cell, cell 1 releases a neurotransmitter (ligand) or "propagate" the signal in the brain. What likely happens to "propagate" the electrical signal from cell one end terminal to cell 2 start receiver side? A) Both A and B B) A neurotransmitter passes between cells and activates the inward ion channel C) None of these answers- neurons only fire based on voltage gated channels D) There is a physical protein linker that pulls on the next neuron to let it know it is its turn to start an action potential

B) A neurotransmitter passes between cells and activates the inward ion channel

If Na+ channels are opened in a cell that was previously at rest, how will the resting membrane potential be affected? A) It becomes more negative. B) It becomes more positive. C) The membrane potential is not affected by Na+ D) It is permanently reset.

B) It becomes more positive.

Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes. This is largely because ___________________. A) RNA bases cannot form hydrogen bonds with each other. B) RNA is single-stranded. C) RNA contains uracil and uses ribose as the sugar. D) RNA nucleotides use a different chemical linkage between nucleotides compared to DNA.

B) RNA is single-stranded.

Which of the following statements about genetic code is correct? A) all codons specify an amino acid B) The genetic code is redundant C) All codons specify more than one amino acid

B) The genetic code is redundant

A potassium channel conducts K+ ions several orders of magnitude better than Na+ ions, because A) the hydrated Na+ ion occupies a larger volume compared to the hydrated K+ ion, and is too large to pass through the channel pore. B) the Na+ ion is too small to interact with the channel in a way that facilitates the loss of water from the ion. C) the Na+ ion is too large to pass through the channel pore. D) the Na+ ion cannot bind to the high-affinity K+-binding sites in the channel pore.

B) the Na+ ion is too small to interact with the channel in a way that facilitates the loss of water from the ion.

Which of the following statements about prokaryotic mRNA molecules is false? Hint: Keep in mind we really focused on discussions in lecture on eukaryotic cells. What aspect of central dogma is not applicable when we are talking about prokaryotic? What don't prokaryotes have? A) mRNAs are not polyadenylated. B) single prokaryotic mRNA molecule can be translated into several proteins. C) Ribosomes must bind to the 5' cap before initiating translation. D) Ribosomes can start translating an mRNA molecule before transcription is complete.

C) Ribosomes must bind to the 5' cap before initiating translation.

Voltage-gated channels contain charged protein domains, which are sensitive to changes in membrane potential. By responding to a threshold in the membrane potential, these voltage sensors trigger the opening of the channels. Which of the following best describes the behavior of a population of channels exposed to such a threshold? A) All channels open completely. B) All channels open partly, each to a different degree. C) Some channels remain closed and some open completely. D) All channels open partly, to the same degree.

C) Some channels remain closed and some open completely.

In the primary research article, why did the authors have to do the research in the first place? A) because some scientists used different detergents and came up with different responses B) because some scientists used different cell types and came up with different answers C) all of these answers (except none of these answers) D) none of these answers E) because the difference in all of the data coming our about lipid rafts was confusing people

C) all of these answers (except none of these answers)

A hungry yeast cell lands in a vat of grape juice and begins to feast on the sugars there, producing carbon dioxide and ethanol in the process: C6H12O6 + 2ADP + 2Pi + H+ 2CO2 + 2CH3CH2OH + 2ATP + 2H2O Unfortunately, the grape juice is contaminated with proteases that attack some of the transport proteins in the yeast cell membrane, and the yeast cell dies. Which of the following could account for the yeast cell's demise? A) diffusion of ATP out of the cell B) toxic buildup of ethanol inside the cell C) inability to import sugar into the cell D) toxic buildup of carbon dioxide inside the cell

C) inability to import sugar into the cell

Our understanding of membrane potential has led to our understanding of how to use drugs to affect cells. For example, many sedatives target the GABA stimulated Cl- channel. GABA is the ligand that normally opens this Chloride channel to allow Chloride to go INTO the cell. In terms of membrane potential, how does Cl- in affect the cell? A) Raises the membrane potential making it easier to fire B) lowers the membrane potential making it easier to fire C) lowers the membrane potential making it harder to fire D) Raises the membrane potential making it harder to fire

C) lowers the membrane potential making it harder to fire

The sigma subunit of bacterial RNA polymerase ___________________. A) recognizes transcription termination sites in the DNA. B) remains part of the polymerase throughout transcription. C) recognizes promoter sites in the DNA. D) contains the catalytic activity of the polymerase.

C) recognizes promoter sites in the DNA.

You have a segment of DNA that contains the following sequence: 5'-GGACTAGACAATAGGGACCTAGAGATTCCGAAA-3' 3'-CCTGATCTGTTATCCCTGGATCTCTAAGGCTTT-5' You know that the RNA transcribed from this segment contains the following sequence: 5'-GGACUAGACAAUAGGGACCUAGAGAUUCCGAAA-3' Which of the following choices best describes how transcription occurs A) the top strand is the template strand; RNA polymerase moves along this strand from 5' to 3' B) the top strand is the template strand; RNA polymerase moves along this strand from 3' to 5 C) the bottom strand is the template strand; RNA polymerase moves along this strand from 3' to 5' D) the bottom strand is the template strand; RNA polymerase moves along this strand from 5' to 3'

C) the bottom strand is the template strand; RNA polymerase moves along this strand from 3' to 5'

Consider the apical location of a particular protein expressed in epithelial cells, illustrated in the figure. Which type of defect described below is the most likely to cause the redistribution of that protein around the entire cell, shown in the figure? A) the truncation of a protein found in the extracellular matrix B) a nonfunctional flippase C) the deletion of a junctional protein D) a nonfunctional protein glycosylase

C) the deletion of a junctional protein

In the primary research article the authors utilized a two step cell extraction method in Figure 1. What was the purpose and order of those steps? A) western blot analysis B) Chemical homogenization to break open and separate with centrifugation to remove the cytoplasm from the membrane and them cell shearing to breakdown the remaining membranes C) Thin layer chromatography D) Cell Shearing to break open and separate the cytoplasm from the membrane and them chemical homogenization to breakdown the remaining membranes

D) Cell Shearing to break open and separate the cytoplasm from the membrane and them chemical homogenization to breakdown the remaining membranes

A poison added to an in vitro translation mixture containing mRNA molecules with the sequence 5'-AUGAAAAAAAAAAAAUAA-3' has the following effect: the only product made is a Met-Lys dipeptide that remains attached to the ribosome. What is the most likely way in which the poison acts to inhibit protein synthesis? A) It inhibits peptidyl transferase activity. B) It inhibits release factor. C) It mimics release factor. D) It inhibits movement of the small subunit relative to the large subunit.

D) It inhibits movement of the small subunit relative to the large subunit.

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant outside a typical mammalian cell? A) Cl- B) K+ C) Ca2+ D) Na+

D) Na+

The ribosome is important for catalyzing the formation of peptide bonds. Which of the following statements is true? A) Once the large and small subunits of the ribosome assemble, they will not separate from each other until degraded by the proteasome. B) The number of rRNA molecules that make up a ribosome greatly exceeds the number of protein molecules found in the ribosome. C) The large subunit of the ribosome is important for binding to the mRNA. D) The catalytic site for peptide bond formation is formed primarily from an rRNA.

D) The catalytic site for peptide bond formation is formed primarily from an rRNA.

Which of the following might decrease the transcription of only one specific gene in a bacterial cell? A) a decrease in the amount of RNA polymerase B) a decrease in the amount of sigma factor C) a mutation that introduced a stop codon into the DNA that precedes the gene's coding sequence D) a mutation that introduced extensive sequence changes into the DNA that precedes the gene's transcription start site

D) a mutation that introduced extensive sequence changes into the DNA that precedes the gene's transcription start site

The figure illustrates changes in membrane potential during the formation of an action potential. What membrane characteristic or measurement used to study action potentials is indicated by the arrow? A) resting membrane potential B) effect of a depolarizing stimulus C) threshold potential D) action potential

D) action potential

In the primary article the authors separated their lipids using thin layer chromatography which separated them based on A) size B) charge C) density D) polarity

D) polarity

Ribozymes catalyze which of the following reactions? A) protein degradation B) transcription C) DNA synthesis D) splicing

D) splicing ( Yes! Not only do . the ribosomes work beacuse RNAs act like enzymes but the spisosome is also made up of RNAs that act the enzymes)

Use the genetic decoder provided to assist in answering this question. Quiz 4 decoder.pdfPreview the document What do you predict would happen if you created a tRNA with an anticodon of 5'-CAA-3' that is charged with methionine, and added this modified tRNA to a cell-free translation system that has all the normal components required for translating RNAs? A) methionine would be incorporated into proteins at some positions where leucine should be B) methionine would be incorporated into proteins at some positions where valine should be C) methionine would be incorporated into proteins at some positions where valine should be D) methionine would be incorporated into proteins at some positions where glutamine should be

A) methionine would be incorporated into proteins at some positions where leucine should be

The plasma membrane serves many functions, many of which depend on the presence of specialized membrane proteins. Which of the following roles of the plasma membrane could still occur if the bilayer were lacking these proteins? A) selective permeability B) import/export of molecules C) intercellular communication D) cellular movement

A) selective permeability

Which of the following statements about the proteasome is false? A) Ubiquitin is a small protein that is covalently attached to proteins to mark them for delivery to the proteasome. B) Proteases reside in the central cylinder of a proteasome. C) Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold. D) The protein stoppers that surround the central cylinder of the proteasome use the energy from ATP hydrolysis to move proteins into the proteasome inner chamber.

C) Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold.

You are studying a disease that is caused by a virus, but when you purify the virus particles and analyze them you find they contain no trace of DNA. Which of the following molecules are likely to contain the genetic information of the virus? A) lipids B) high energy hydride ions from NADH C) RNA D) sugars

C) RNA

The concentration of a particular protein, X, in a normal human cell rises gradually from a low point, immediately after cell division, to a high point, just before cell division, and then drops sharply. The level of its mRNA in the cell remains fairly constant throughout this time. Protein X is required for cell growth and survival, but the drop in its level just before cell division is essential for division to proceed. You have isolated a line of human cells that grow in size in culture but cannot divide, and on analyzing these mutants, you find that levels of X mRNA in the mutant cells are normal. Which of the following mutations in the gene for X could explain these results? A) the introduction of a stop codon that truncates protein X at the fourth amino acid B) a change of the first ATG codon to CCA C) a change at a splice site that prevents splicing of the RNA D) the deletion of a sequence that encodes sites at which ubiquitin can be attached to the protein

D) the deletion of a sequence that encodes sites at which ubiquitin can be attached to the protein

Which of the following concentration gradients is considered a passive movement of a ions? A) None of these answers B) Na+ moves into the cell C) Ca2+ moves into the cytosol D) K+ moves out of the cell E) All of these answers (except none of these answers)

E) All of these answers (except none of these answers)