36. The double bonds in naturally-occuring fatty acids are usually isomers. A. cis B. trans C. both cis and trans D. D- E. L-

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1 36. The double bonds in naturally-occuring fatty acids are usually isomers. A. cis B. trans C. both cis and trans D. D- E. L- 37. The essential fatty acids are A. palmitic acid B. linoleic acid C. linolenic acid D. both A and B E. both B and C 38. Phospholipids are A. found only on the cytosolic side of the plasma membrane B. cellular energy sources C. structural components of membranes D. found in ribosomes E. all of the above 39. The preferred energy source of the brain is A. fatty acids B. ketone bodies C. ribose D. glucose E. asparagine 40. The fluidity of a membrane is largely determined by its percentage of A. phosphatidyl choline B. phosphatidyl ethanolamine C. cholesterol D. unsaturated fatty acids E. both C and D 41. Energy requiring transport mechanisms include A. simple diffusion B. active transport C. receptor-ligand binding D. facilitated diffusion E. both A and B

2 42. Glutamate is the precursor of all of the following amino acids EXCEPT A. proline B. arginine C. ornithine D. glutamine E. lysine 43. Which of the following statement concerning THF (tetrahydrofolate) is NOT correct? A. The source of one-carbon units for THF transfer is serine. B. THF derivatives are involved in the synthesis of purine bases. C. Methyl groups are transferred from methylthf to SAM. D. THF is oxidized to DHF during the synthesis of thymidine nucleotides. E. Humans synthesize THF from acetyl CoA. 44. The oxidation state of the methenyl group (-CH=) is comparable to that of A. methane B. methanol C. formaldehyde D. formic acid E. carbon monoxide 45. All of the following are carriers of single carbons for biosynthesis EXCEPT A. choline B. biotin C. tetrahydrofolate (THF) D. S-adenosylmethionine (SAM) E. carnitine 46. All of the following are purine bases except A. guanine B. adenine C. xanthine D. thymine E. hypoxanthine 47. Which of the following molecules does NOT activate a protein kinase? A. insulin B. camp C. diacylclycerol (DAG) D. AMP E. carnitine

3 48. According to the central dogma of biology, genetic information flows in the following direction A. RNA --> protein --> DNA B. RNA --> DNA --> protein C. protein --> RNA --> DNA D. DNA --> RNA --> protein E. protein --> DNA --> RNA 49. are RNA products of gene sequences that code for a protein. A. introns B. exons C nucleosomes D. rrnas E. helicases 50. Elements of condensation of DNA include all of the following EXCEPT A. nucleosomes B. supercoiling C. histones D. fatty acids E. All of the above are involved. 51. All of the following proteins are involved in DNA replication EXCEPT A. the replication fork. B. DNA polymerase. C. primase D. DNA ligase E. helicase 52. All of the following are essential amino acids except A. phenylalanine B. valine C. cysteine D. histidine E. leucine 53. A codon is a three-nucleotide sequence of A. trna B. DNA, read in the 5' to 3' direction C. mrna, read in the 5' to 3' direction D. rrna E. mrna, read in the 3' to 5' direction

4 54. The sequence of a DNA strand is 5'---pApGpCpG--3'. The sequence of a complementary segment of DNA is: A. 5'--pTpCpGpC--3' B. 5'--pCpGpCpU--3' C. 5'--pCpApTpA--3' D. 5'--pCpGpCpT--3' E. 5'--pUpCpGpC--3' 55. Which of the following provides the energy to move the ribosome along the mrna? A. ATP B. datp C. GTP D. UTP E. dutp 56. Molecules involved in purine nucleotide synthesis include all of the following EXCEPT: A. Phosphoribosyl pyrophosphate (PRPP) B. Aspartate C. S-adenosylmethionine (SAM) D. N 10 -formyl THF E. CO Which of the following statements is FALSE? A. There is at least one trna for each of the amino acids. B. The attachment site for the amino acid is at the 3' end of the trna molecule. C. Each trna accepts a specific amino acid. D. A, C, G and U are the only bases in trna. E. There is a specific trna for initiation of protein synthesis. 55. Indicate where in the eukaryotic cell the following processes take place: (2 pts each) A. Glycolysis B. Urea Cycle C. DNA replication D. RNA synthesis E. Fatty acid synthesis F. Protein synthesis G. Fatty acid oxidation

5 56. Mark each of the following statements T (true) or F (false) (1 pt each) Acyl carrier protein is the principal regulated protein of fatty acid synthesis. Ribonucleotides are reduced to deoxyribonucleotides at the di- phosphorylation level. Membranes are phospholipid monolayers containing imbedded proteins. Carbon atoms in the purine base ring structure come from CO 2, N 5,N 10 - formylthf and alanine. Most phospholipids contain glycerol, two fatty acids, phosphate and an organic base. DNA replication is semi-conservative. DNA with high GC content has a lower melting point than DNA with high AT content. Eukaryotic DNA is linear. Okazaki fragments are involved in the synthesis of the lagging strand of DNA during replication. RNA polymerases require a primer. The sense of the strands in the DNA double helix is anti-parallel. In eukaryotes, all proteins are synthesized in the compartment in which they will function. DNA polymerase I does not require a template. The link between nucleotides in RNA and DNA is a phosphodiester bond. RNA polymerase binds to DNA at promoter regions. 57. On the last page is a genetic code table. Determine the sequence of the protein segment that would be synthesized by transcription and translation of the following DNA sequence. (Assume that his sequence is in the middle of the gene, i.e., no start codon is needed.) 5' -paptpcpcpcpgpgpapcpcpapt- 3' 3' - TpApGpGpGpCpCpTpGpGpTpAp- 5'

6 THE GENETIC CODE First position Second Position Third position 5' end U C A G 3' end Phe Ser Tyr Cys U U Phe Ser Tyr Cys C Leu Ser STOP STOP A Leu Ser STOP Trp G Leu Pro His Arg U C Leu Pro His Arg C Leu Pro Gln Arg A Leu Pro Gln Arg G Ile Thr Asn Ser U A Ile Thr Asn Ser C Ile Thr Lys Arg A Met Thr Lys Arg G Val Ala Asp Gly U G Val Ala Asp Gly C Val Ala Glu Gly A Val Ala Glu Gly G

Basic concepts of molecular biology

Basic concepts of molecular biology Gabriella Trucco Email: gabriella.trucco@unimi.it Life The main actors in the chemistry of life are molecules called proteins nucleic acids Proteins: many different