複選題

34. Which of the following descriptions about eukaryotic cells are CORRECT?
(A) Eukaryotic cells gain many advantages from organelle development.
(B) Phospholipids are the conserved building blocks of cellular membranes.
(C) Eukaryotic cells utilize a similar cycle to regulate their division.
(D) The genetic information is carried and passed by the messenger ribonucleic acid (mRNA) in most eukaryotes.
(E) Bacteria are eukaryotes and widely used in biology research.

30. You are studying the function of a recently identified gene in C. elegans. You have been performing genetic screens for several months in an attempt to isolate loss-of-function mutations in this gene, but unfortunately you have been unsuccessful. Your advisor suggests that you try another approach to eliminate gene function. Which of the following techniques would accomplish this goal? (A) Design a repressor to bind to the operon of this gene. (B) Use a histone deacetylase to induce a transcriptionally inactive state. (C) Use RNA interference to prevent mRNA translation. (D) Use a wild type strain and mutagenize it with a UV light. (E) Use antisense DNA to block RNA transcription.

複選題31. Proteins give cells structure and perform most cellular tasks, thus functions of proteins could be regulated via several different ways. Which of the following descriptions about regulating protein function are CORRECT? (A) Proteins are regulated at the level of synthesis, degradation or the intrinsic activity. (B) Proteins are marked for degradation with ubiquitin tag and then degraded within proteasomes or lysosomes. (C) Ubiquitination of proteins is irreversible. (D) Phosphorylation and dephosphorylation covalently regulate protein activity. (E) Protein activity could be regulated by controlling protein location and concentration.

32. Upon adding more NaCl into a protein solution, the electrostatic interaction between charged groups on the protein surface will be (A) strengthened due to ion exchange. (B) strengthened due to charge induction effect. (C) weakened due to charge induction effect. (D) weakened due to shielding effect. (E) will not be effected.

複選題33. Once transcription is finished and the primary RNA transcript is produced, it must undergo various processing reactions to yield functional RNAs. Which of the following descriptions about pre-mRNA processing are CORRECT? (A) In eukaryotic cells, pre-mRNAs are processed by 5' capping, 3' cleavage, polyadenylation and splicing in the cytoplasm. (B) Spliceosome is a large ribonucleoprotein complex catalyzing two transesterification reactions that joint two exons and remove the intron as a lariat structure. (C) Translation can be repressed by micro RNAs (miRNAs), which form imperfect hybrids with sequences in the 3' untranslated region (UTR) of specific target mRNAs. (D) RNA interference, which probably evolved as an early defense system against viruses and transposons, leads to degradation of mRNAs that form perfect hybrids with short interfering RNAs (siRNAs). (E) Many mRNA are transported to specific subcellular location by sequence-specific DNA-binding protein thus permit production of proteins at specific regions.

複選題35. Which of the flowing descriptions about gene structure and chromosomal organization are CORRECT? (A) A gene is the entire DNA sequence required for synthesis of a functional protein or RNA molecule, including coding region, control region and intron. (B) Many genes encode functional RNAs that are not translated into proteins but perform significant functions, such as rRNA, tRAN, and snRNAs. Among these are the exception micro RNAs (miRNAs), although up to 1000 in humans, have no any biological significance. (C) Although DNA transposons occur in eukaryotes, retrotransposons generally are much more abundant in vertebrates. (D) Each eukaryotic chromosome contains a single DNA molecular packaged into nucleosomes and folded into a 30-nm chromatin fiber. (E) In eukaryotic cells, the organization of DNA into chromatin allows a mechanism for regulation of gene expression.

複選題36. Which of the flowing descriptions about transcriptional control of gene expression are CORRECT? (A) Gene expression in both prokaryotes and eukaryotes is regulated primarily by mechanisms that control the initiation of transcription. (B) The primary purpose of gene control in multicellular organisms is the execution of precise developmental decisions so that the proper genes are expressed in the proper cells. (C) Enhancers direct binding of RNA polymerase II to DNA, determine the site of transcription initiation, and influence transcription rate. (D) The activity of many transcription factors are indirectly regulated by binding of extracellular proteins and peptides to cell-surface receptors. (E) Epigenetic control of transcription refers to repression or activation that is maintained after cells replicate as the result of DNA methylation or post-translational modification of histones.

複選題37. The advanced fluorescent microscopy not only leads the development of cell biology, but also facilitates the progress of molecular biology. Which of the following descriptions about microscopy are CORRECT? (A) The resolution of light microscope, about 0.2 micro-meter, is limited by the wavelength of light. (B) Confocal microscopy provides better resolution in fluorescent imaging by removing out-of-focus fluorescent signals. (C) Electron microscopy gives better resolution by providing shorter wavelength of illumination source. (D) Total internal refection fluorescence (TIRF) microscopy allows fluorescent sample very close to a coverslip to be seen with great clarity. (E) Super-resolution microscopy allows for detailed fluorescent images at nanometer resolution by using shorter wavelength of light.

複選題38. Plasma membrane defines the cell and separates the inside from the outside. Which of the following descriptions about the characteristics of biomembranes are CORRECT? (A) Biomemrbranes contain three principle classes of lipids: phosphoglycerides, sphingolipids and sterols. (B) Most lipids and many proteins are laterally mobile in biomembranes. (C) The asymmetry of lipid composition across the membrane bilayer is a characteristic of all biomembranes, yet the lipid composition would not influence the physical properties of membranes. (D) The shape of membrane can be changed by transmembrane or peripheral membrane proteins. (E) Lipid droplets are storage vesicles for lipids, originating in the ER.

複選題39. The existence of water channel had been proposed since 1970 but was eventually identified till 1992 by Peter Agre. Which of the following sentences could support the existing of water channel on the membrane of a cell? (A) The transport of water is ATP-independent. (B) Red blood cells, but not the frog eggs, swell with water. (C) Mercurials would inhibit water transport in red blood cells. (D) There is a maximal rate (Vmax) for water transport of red blood cells. (E) Water (H2O) crosses through the red blood cell membrane with almost no resistance, while acid hydronium ion (H3O+) does not permeate.

複選題40. Cells convert external nutrients as sources of energy into biologically universal, intracellular, chemical energy carrier, adenosine triphosphate (ATP). Which of the following descriptions about cellular energetics are CORRECT? (A) Glucose oxidation in eukaryotic cells can be divided into four stages: glycolysis, citric acid cycle, electron transport chain and ATP synthesis, where all take place in mitochondria. (B) The oxidation of short- to long-chain fatty acids occurs in mitochondria with production of ATP, whereas oxidation of very long-chain fatty acids occurs primarily in peroxisomes and is not linked to ATP production. (C) The rate of glucose oxidation via glycolysis is regulated by the inhibition or stimulation of several enzymes, depending on the cell's need for ATP. (D) Neither glycolysis nor the citric acid cycle directly use molecular oxygen. (E) ATP synthase catalyzes ATP synthesis as electron flow through the inner mitochondrial membrane down their electrochemical gradient.