Kopiereg voorbehou/copyright reserved Faculty of Natural and Agricultural Sciences / Fakulteit Natuur- en Landbouwetenskappe Department of Biochemistry / Departement Biochemie Lipid and Nitrogen metabolism 261 / Lipied-en stikstofmetabolisme 261 SEMESTER TEST 1 / SEMESTERTOETS 1 BSc Biochemistry / BSc Biochemie Time / Tyd: 1 hour/ 1 uur BCM 261 15 September 2016 /15 September 2016 Total/Totaal: 60 marks / 60 punte Internal examiner / Interne eksaminator: Internal moderator / Interne modereerder External moderator/ Eksterne modereerder Miss N Gama Prof A Neitz Prof A. Louw Instructions/ Instruksies: Answer all the questions. / Beantwoord al die vrae. The question paper consists of 11 pages. / Die vraestel bestaan uit 11 bladsye. Question /Vraag Maximum/ Maksimum Marks / Punte 1 10 2 10 3 10 4 10 5 10 6 10 Total/Totaal: 60 /60 Page 1 of 11
QUESTION/ VRAAG 1 (10) Define the following terms associated with the metabolism of nitrogen/ Definieer die volgende terme geassosieerd met die metabolisme van stikstof: A. Nitrogen fixation/ Stikstof-fiksasie (2) The incorporation of inorganic molecular nitrogen in the atmosphere first into ammonia then organic compounds used by the organism. / The conversion of molecular nitrogen to ammonia. B. Nitrogen assimilation/ Stikstof-assimilasie (2) The incorporation of produced ammonia into biological compounds such as amino acids. C. Essential amino acids/ Essensiële aminosure (2) An amino acid that cannot be synthesized by the body and must be obtained through diet. D. Purine salvage reactions/ Purien herwinningsreaksies (2) Reactions that reuse compounds that require a large amount of energy to produce. E. Glucogenic amino acids/ Glukogeniese aminosure (2) An amino acid that has pyruvate or oxaloacetate as a catabolic breakdown product. Page 2 of 11
QUESTION / VRAAG 2 (10) Answer the following questions by writing down the letter that corresponds to the correct answer. There is only one correct answer for each question. Write the letter of your choice in the box provided. / Beantwoord die volgende vrae deur die letter te gee wat ooreenstem met die korrekte antwoord. Daar is slegs een antwoord vir elke vraag. Skryf die letter van jou keuse in die boks voorsien. A. D B. A C. B D. A E. C F. C G. C H. D I. A J. B Page 3 of 11
QUESTION / VRAAG 3 (10) State whether the following statements are TRUE or FALSE, and GIVE A REASON for your statement./ Dui aan of die volgende stellings WAAR of ONWAAR is en GEE n REDE daarvoor A. Ribose-5-phosphate is the precursor molecule for the aromatic family of amino acids./ Ribose-5- fosfaat is die voorloper-molekuul vir die aromatiese familie van aminosure (2) False. Ribose-5-phosphate is the precursor for the histidine family of amino acid./ Phosphoenol pyruvate and Erythrose-4-phosphate are the precursors for the aromatic family of amino acids B. The citric acid cycle is amphibolic. / Die sitroensuur-siklus is amfibolies (2) True. The citric acid cycle has a part in both amino acid catabolism and anabolism. C. Pyridoxal phosphate only participates in transamination reactions. / Piridoksaal-fosfaat neem alleenlik deel in transaminasie-reaksies (2) False. Pyridoxal phosphate also participates in decarboxylation and racemization reactions. D. Gout occurs due to the inhibition of the enzyme xanthine oxidase./ Jig kom voor as gevolg van inhibisie van die ensiem xantien-oksidase (2) False. Gout occurs due to over production of Uric acid (Xanthine oxidase is active). E. ATCase in pyrimidine synthesis is inhibited by UMP/ ATCase in pirimidien-sintese word deur UMP geïnhibeer (2) False. ATCase is inhibited by CTP./ UMP inhibits CPS-II (carbomoyl phosphate synthetase). Page 4 of 11
QUESTION / VRAAG 4 (10) Answer the following questions: Antwoord die volgende vrae A. Refer to the reaction below and label i, ii and iii./ Verwys na die reaksie hieronder en benaam i, ii en iii (3) i- NH 4 + (Ammonium) ii- ATP iii- ADP + P B. The common name of reactions where glutamine donates an amino group is known as:/ n Algemene naam vir reaksies waartydens glutamien n aminogroep skenk is bekend as: Transamination reactions (1) C. Label the following structures and state what type of carriers they are/ Benaam die volgende strukture en meld watter tipe van draers hulle is: (6) i- Folic Acid (Tetrahydrofolate/ THF), methyl carrier/ formyl carrier ii- PAPs (3 -Phospho-5 -adenylyl-sulfate), sulphide carrier (S 2- ) iii- SAM (S-adenosylmethionine), methyl carrier Page 5 of 11
QUESTION / VRAAG 5 (10) Refer to the reaction below and answer the following questions:/ Verwys na die reaksie hieronder en beantwoord die volgende vrae: A. Where does this reaction take place during the urea cycle?/ Waar vind hierdie reaksie plaas tydens die ureum-siklus? (1) Mitochondria B. What is the name of the enzyme catalyzing the above reaction? / Wat is die naam van die ensiem wat die bostaande reaksie kataliseer? (1) Carbomoly phosphate synthetase 1 (CPS-1) C. What are the effects of increased arginine concentrations on the enzyme catalyzing the above reaction? / Wat is die effekte van verhoogde arginien-konsentrasies op die ensiem wat bostaande reaksie kataliseer? (4) High [Arginine] will result in the activation of N-acetylglutamate synthase which results in the formation of N-acetylglutamate. N- acetylglutamate will then activate CPS-1 resulting in increases in the rate of the urea cycle. D. How would the above reaction differ in the synthesis of pyrimidines? / Hoe sou die bostaande reaksie verskil in die sintese van pirimidiene? (3) In pyrimidine synthesis the location is the nitrogen donor is glutamine, the enzyme catalyzing the reaction is CPS-II and the reaction takes place in the cytosol. E. In pyrimidine synthesis, the enzyme that catalyzes the production of carbamoyl phosphate is feedback inhibited by which compound?/ In pirimidien-sintese, word die ensiem wat die produksie van karbamoïelfosfaat kataliseer deur terugvoer geïnhibeer deur watter verbinding? (1) The enzyme is feedback inhibited by UMP Page 6 of 11
QUESTION/ VRAAG 6 (10) Refer to the reaction below and answer the following questions/ Verwys na die onderstaande reaksie en beantwoord die volgende vrae: A. Give the name and structure of i./ Gee die naam en struktuur van i (2) B. What type of reaction is depicted above?/ Watter tipe van reaksie word hierbo gewys? A one-carbon transfer reaction. (1) C. The produced N 5, N 10 -methylene tetrahydrofolate participates in thymidine synthesis in the reaction below. Give labels ii to vi./ Die geproduseerde N 5,N 10 -metileen tetrahidrofolaat neem deel aan timidien-sintese in die reaksie hieronder. Benaam ii tot vi. (7) iiiii- dump ivv- dtmp vi- Thymidylate synthase Page 7 of 11
Page 8 of 11