Biochemistry Practice Exam II

BIOCHEMISTRY EXAMS 2 NAME ______________________________________________________________ Attempt all questions. Read each question carefully before answering. Make sure to have your name on this test paper and the scantron. Multiple Choice Questions (2 points each) 1. When two carbohydrates are epimers: A) B) C) D) E) one is a pyranose, the other a furanose. one is an aldose, the other a ketose. they differ in length by one carbon. they differ only in the configuration around one carbon atom. they rotate plane-polarized light in the same direction. 2. The basic structure of a proteoglycan consists of a core protein and a: A) B) C) D) E) glycolipid. glycosaminoglycan. lectin. lipopolysaccharide. peptidoglycan. 3. In glycoproteins, the carbohydrate moiety is always attached through the amino acid residues: A) B) C) D) E) asparagine, serine, or threonine. aspartate or glutamate. glutamine or arginine. glycine, alanine, or aspartate. tryptophan, aspartate, or cysteine. 4. Which of the following is a dominant feature of the outer membrane of the cell wall of gram negative bacteria? A) B) C) D) E) Amylose Cellulose Glycoproteins Lipopolysaccharides Lipoproteins 5. In DNA sequencing by the Sanger (dideoxy) method: 1 A) radioactive dideoxy ATP is included in each of four reaction mixtures before enzymatic synthesis of complementary strands. B) specific enzymes are used to cut the newly synthesized DNA into small pieces, which are then separated by electrophoresis. C) the dideoxynucleotides must be present at high levels to obtain long stretches of DNA sequence. D) the role of the dideoxy CTP is to occasionally terminate enzymatic synthesis of DNA where Gs occur in the template strands. E) the template DNA strand is radioactive. 6. A convenient cloning vector with which to introduce foreign DNA into E. coli is a(n): A) B) C) D) E) E. coli chromosome. messenger RNA. plasmid. yeast "ARS" sequence. yeast transposable element. 7. Based on Chargaff's rules, which of the following are possible base compositions for doublestranded DNA? %A %G %C %T %U 5 45 45 5 0 A) B) 20 20 20 20 20 35 15 35 15 0 C) D) all of the above E) none of the above 8. The double helix of DNA in the B-form is stabilized by: A) covalent bonds between the 3' end of one strand and the 5' end of the other. B) hydrogen bonding between the phosphate groups of two side-by-side strands. C) hydrogen bonds between the riboses of each strand. D) nonspecific base-stacking interaction between two adjacent bases in the same strand. E) ribose interactions with the planar base pairs. 9. Fatty acids: a. are highly oxidized storage forms of hydrocarbons. b. are referred to as “saturated” if they have one or more C–C double bonds. c. are usually (but not always) unbranched. d. by definition, never exceed 20 carbons in length. 10. Which statement regarding linoleic acid (18:29,12) is FALSE? (a) It has 20 carbons. (b) It has two double bonds. (c) It has one carboxylic acid functional group (d) It has a C–C double bond between carbons 9 and 10. 2 11. Vitamin A1 and its derivatives: a. contain only trans C–C double bonds. b. are not stored in the body in significant amounts. c. act as antioxidants. d. are involved in regulating cell growth and differentiation. 12. A new plasmid can be purchased from a major supplier who claims it has the largest polylinker available. What is unique about this new plasmid? A. The plasmid can accept the longest DNA sequence insert compared with any other plasmid. B. It is the largest plasmid available based on base-pair size. C. It has the largest number of maintenance genes of any available plasmid. D. There are more endonuclease sites than any other plasmid. E. It is possible to incorporate more inserts than any other plasmid. 13. Why would a lab technician choose a bacterial artificial chromosome for cloning a gene, rather than a plasmid? A. because the DNA insert is from genomic DNA and not plasmid DNA B. because the insert to be cloned is very large C. because bacterial DNA will be used to make many copies of the gene (i.e., clone it) D. because the gene insert will eventually be used to transform cells, meaning incorporate the gene into genomic DNA E. because work on the gene will only be performed in a cell-free system, one without the genomic DNA required for cloning 14. ( 10 points) Carbohydrates: In the following structure: (a) How many of the monosaccharide units are furanoses and how may are pyranoses? (b) What is the linkage between the two monosaccharide units? (c) Is this a reducing sugar? Explain. (d) Convert this structure to linear form and name the sugar. 3 (e) How many chiral centers does the above sugar (in d) have and how many stereoisomers are theoretically possible for this aldohexose? 15. (10 points) Nucleotides (a) Compounds that contain a nitrogenous base, a sugar, and a phosphate group are called _________________. Two purines found in DNA are ______________ and __________________. A pyrimidine found in all DNA but in only some RNA is _________________. In DNA, the base pair ___-___ is held together by three hydrogen bonds; the base pair ___-___ has only two such bonds. (c) What is the approximate length of a DNA molecule (in the B form) containing 10,000 base pairs? (1 nucleotide has an approximate length of 3.4 Å) 16. (10 points) DNA Technology (a) Explain how each of the following is used in cloning in a plasmid: (a) antibiotic resistance genes; (b) origin of replication; (c) polylinker region. 4 (b) Several vectors can be used in the cloning. List these vectors and state the disadvantage of one. . 17. (4 points) List 4 sources of mutation in the DNA given specific examples of each. 18. (6 points) Describe the dependence of the melting point of a fatty acid upon (a) chain length and (b) unsaturation; (c) explain these dependencies in molecular terms. 19. (4 points What is the most significant chemical difference between triacylglycerols and glycerophospholipids that leads to their different functions? Discuss these functions. 20. (6 points) For each of the following polysaccharides state the monomers, the type of linkages present and function. Polysaccharide Glycogen Monomers Type of linkages Function 5 Cellulose Peptidoglycan Bonus points. 1. What is the name of the heat-stable DNA polymerase used in PCR? What is PCR? 6