Cell Bio Practice Exam 2|32 Questions with Verified Answers
RNA in cells differs from DNA in that ___. - CORRECT ANSWER it is single-stranded and can
... [Show More] fold up into a variety of structures
Transcription is similar to DNA replication in that ___. - CORRECT ANSWER nucleotide polymerization occurs only in the 5′-to-3′ direction.
Which of the following statements is FALSE? (a) A new RNA molecule can begin to be synthesized from a gene before the previous RNA molecule's synthesis is completed. (b) If two genes are to be expressed in a cell, these two genes can be transcribed with different efficiencies. (c) RNA polymerase is responsible for both unwinding the DNA helix and catalyzing the formation of the phosphodiester bonds between nucleotides. - CORRECT ANSWER (d) Unlike DNA, RNA uses a uracil base and a deoxyribose sugar.
Which of the following statements is FALSE? (a) RNA polymerase can start making a new RNA molecule without a primer; DNA polymerase cannot. (b) RNA polymerase does not proofread its work; DNA polymerase does. (c) RNA polymerase catalyzes the linkage of ribonucleotides while DNA polymerase catalyzes the linkage of deoxyribonucleotides. (d) RNA polymerase adds bases in a 3′-to-5′ direction; DNA polymerase adds bases in a 5′-to-3′ direction. - CORRECT ANSWER (d) RNA polymerase adds bases in a 3′-to-5′ direction; DNA polymerase adds bases in a 5′-to-3′ direction.
Which one of the following is the main reason that a typical eukaryotic gene is able to respond to a far greater variety of regulatory signals than a typical prokaryotic gene or operon? (a) Eukaryotes have three types of RNA polymerase. (b) Eukaryotic RNA polymerases require general transcription factors. (c) The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter. (d) Prokaryotic genes are packaged into nucleosomes. - CORRECT ANSWER The transcription of a eukaryotic gene can be influenced by proteins that bind far from the promoter.
Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus? (a)The ribosome binds to the mRNA. (b) The mRNA is polyadenylated at its 3′ end. (c) A guanine nucleotide with a methyl group is added to the 5′ end of the mRNA. (d) RNA polymerase dissociates. - CORRECT ANSWER (a)The ribosome binds to the mRNA.
Which of the following statements about the genetic code is CORRECT? (a) All codons specify more than one amino acid. (b) The genetic code is redundant. (c) All amino acids are specified by more than one codon. (d) All codons specify an amino acid. - CORRECT ANSWER The genetic code is redundant.
A neuron and a white blood cell have very different functions. For example, a neuron can receive and respond to electrical signals, while a white blood cell defends the body against infection. This is because ___. (a) all of the proteins found in a neuron are completely different from the proteins found in a white blood cell. (b) the neuron and the white blood cell within an individual have the same genome.(c) the neuron expresses some mRNAs that the white blood cell does not. (d) neurons and white blood cells are differentiated cells and thus no longer need to transcribe and translate genes. - CORRECT ANSWER the neuron expresses some mRNAs that the white blood cell does not.
The distinct characteristics of different cell types in a multicellular organism result mainly from the differential regulation of the ___. (a) replication of specific genes. (b) transcription of genes transcribed by RNA polymerase II. (c) transcription of housekeeping genes. (d) proteins that directly bind the TATA box of eukaryotic genes. - CORRECT ANSWER transcription of genes transcribed by RNA polymerase II
The human genome encodes about 21,000 protein-coding genes. Approximately how many such genes does the typical differentiated human cell express at any one time? (a) 21,000—all of them (b) between 18,900 and 21,000—at least 90% of the genes (c) between 5000 and 15,000 (d) less than 2100 - CORRECT ANSWER between 5000 and 15,000
Which of the following statements about differentiated cells is TRUE? (a) Cells of distinct types express nonoverlapping sets of transcription regulators. (b) Once a cell has differentiated, it can no longer change its gene expression. (c) Once a cell has differentiated, it will no longer need to transcribe RNA. (d) Some of the proteins found in differentiated cells are found in all cells of a multicellular organism. - CORRECT ANSWER Some of the proteins found in differentiated cells are found in all cells of a multicellular organism.
Which of the following statements about transcriptional regulators is FALSE? (a) Transcription regulators interact only with the sugar-phosphate backbone on the outside of the double helix to determine where to bind on the DNA helix. (b) Transcription regulators will form hydrogen bonds, ionic bonds, and hydrophobic interactions with DNA. (c) The DNA-binding motifs of transcription regulators usually bind in the major groove of the DNA helix. (d) The binding of transcription regulators generally does not disrupt the hydrogen bonds that hold the double helix together. - CORRECT ANSWER Transcription regulators interact only with the sugar-phosphate backbone on the outside of the double helix to determine where to bind on the DNA helix.
Which of the following is NOT involved in post-transcriptional control? (a) the spliceosome (b) Dicer (c) Mediator (d). RISC - CORRECT ANSWER mediator
miRNAs, tRNAs, and rRNAs all ___. (a)do not code for proteins. (b). act in the nucleus. (c) are packaged with other proteins to form RISC. (d) form base pairs with mRNA molecules. - CORRECT ANSWER do not code for proteins.
MicroRNAs __. (a) are produced from a precursor miRNA transcript. (b) are found only in humans. (c) control gene expression by base-pairing with DNA sequences. (d) can degrade RNAs by using their intrinsic catalytic activity. - CORRECT ANSWER are produced from a precursor miRNA transcript
Which of the following statements about miRNAs is FALSE? (a) One miRNA can regulate the expression of many genes. (b) miRNAs are transcribed in the nucleus from genomic DNA. (c) miRNAs are produced from rRNAs. (d) miRNAs are made by RNA polymerase. - CORRECT ANSWER miRNAs are produced from rRNAs.
Which of the following statements about RNAi is TRUE? (a) The RNAi mechanism is found only in plants and animals. (b) RNAi is induced when double-stranded, foreign RNA is present in the cell. (c) RISC uses the siRNA duplex to locate complementary foreign RNA molecules. (d) siRNAs bind to miRNAs to induce RNAi. - CORRECT ANSWER RNAi is induced when double-stranded, foreign RNA is present in the cell.
The properties of a lipid bilayer are determined by the structures of its lipid molecules. Predict the properties of the lipid bilayers that would result if the following was the case: phospholipids had only one hydrocarbon chain instead of two.
(a) still form bilayers (b)form micelles rather than bilayers. - CORRECT ANSWER form micelles rather than bilayers.
The properties of a lipid bilayer are determined by the structures of its lipid molecules. Predict the properties of the lipid bilayers that would result if the following was the case: if all of the hydrocarbon chains were saturated, ___.
(a) Bilayers formed by lipids with saturated hydrocarbon tails would be much less fluid. (b) Their fatty acid tails are trans-conformation - CORRECT ANSWER Bilayers formed by lipids with saturated hydrocarbon tails would be much less fluid.
Which one of the followings proteins contains a single Transmembrane (TM) region?
(a) Growth factor receptor (Receptor Tyrosine Kinase) (b) Sos (c) Ras - CORRECT ANSWER Growth factor receptor (Receptor Tyrosine Kinase)
Which of the following events in necessary for establishing lipid anchor of a membrane protein on the extracellular side?
(a) Myristoylation (b) Prenylation (c) Glycosylphosphatidylinositol (GPI) anchor (d) Ubiquitylation - CORRECT ANSWER Glycosylphosphatidylinositol (GPI) anchor
A biological membrane can be solubilized with a mild detergent such as Triton X-100. The shape of the phospholipids in the mixed micelle is _____. (a) a cone (b) a cylinder (c) a cube (d) an Icosahedron - CORRECT ANSWER cylinder
You generated a light activatable chloride channel and successfully expressed it in a mouse neuron of which function is not known. During the period of the channel activation, the mouse failed to make any memory. What can you say from the experiment?
(a) The targeted neuron is positively involved in memory formation. (b) The targeted neuron is negatively involved in memory formation.
(c) The targeted neuron is not involved in memory formation. - CORRECT ANSWER The targeted neuron is positively involved in memory formation.
Some proteins are almost as mobile as lipids, whereas others are virtually immobile. Which of the following proteins would be the fastest moving membrane protein? (a) fibronectin, a peripheral glycoprotein that interacts with the extracellular matrix. (b) Bacterial rhodopsin a 7-TM protein (c) E-Cadherin at the cell-cell junction linked to the F-Actin - CORRECT ANSWER Bacterial rhodopsin a 7-TM protein
Which of the following ions has the highest cytosolic concentration? (a) Na+ (b) K+ (c) Mg2+ (d) Ca2+ - CORRECT ANSWER K
Which of the following ions has the lowest cytosolic concentration? (a) H+ (b) K+ (c) Mg2+ (d) Ca2+ - CORRECT ANSWER H
Cells with aquaporin channels in the plasma membrane can NOT maintain electrochemical gradient. Is this statement true or false?
(a) True (b) False - CORRECT ANSWER False
If all the sodium glucose symporter and the glucose uniporter localize to the basal membrane of the intestinal epithelial cells (facing the connective tissue), what would be the happening? (a) Glucose molecules would flow from the epithelial cells to the connective tissue (b) Glucose molecules would shuttle between the connective tissue and the epithelial cells (c) Glucose molecules would be depleted from the epithelial cells (d) Glucose molecules cannot be transported to the connective tissue from the epithelial cells - CORRECT ANSWER Glucose molecules would shuttle between the connective tissue and the epithelial cells
Macrophages remove dead cells by recognizing a signal on their targets: apoptosed cells populate phosphatidylserine on their outer leaflet, but not the healthy ones. If you have a mutant cell that is efficiently phagocytosed by macrophages, what would be the problem of the mutant cell?
(a) The mutant cells failed to keep the Phosphatidylserine in the inner leaflet of their plasma membrane. (b) The mutant cells failed to keep the Phosphatidylserine in the outer leaflet of their plasma membrane. (c) The mutant cells have excessive flippase activity and thus the Phosphatidylserine stay exclusively at the inner leaflet of the plasma membrane. - CORRECT ANSWER The mutant cells failed to keep the Phosphatidylserine in the inner leaflet of their plasma membrane.
The resting membrane potential of an animal cell _____. (a) has a negative value that can be changed into a positive value (b) is generated by the Calcium ATPase that pumps out positively charged Calcium ions from the cell (c) is generated by the Sodium/Potassium ATPase that pumps out positively charged ions from the cell (d) is generated by the sodium leak channel - CORRECT ANSWER has a negative value that can be changed into a positive value
Which of the following statement is true? (a) During the action potential propagation, the unidirectional propagation of the action potential is mediated by sodium potassium pump. (b) During the action potential propagation, the three distinct forms (conformations) of the voltage sensitive potassium channel spatially localize around region of the action potential. (c) During the action potential propagation, the three distinct forms (conformations) of the voltage sensitive calcium channel spatially localize around region of the action potential. (d) The sodium ions entering the axon through the voltage sensitive sodium channel diffuse randomly. - CORRECT ANSWER The sodium ions entering the axon through the voltage sensitive sodium channel diffuse randomly.
Which membrane lipid does not contain a fatty acid tail - CORRECT ANSWER cholesterol [Show Less]