bchem EOY 2014 (2) — Past Paper Questions & Answers

Biochemistry EOY 2014 — Complete Scanned Examination All 12 scanned pages were processed locally. The source contains multiple sections, including structured and multiple-choice questions. Page context is preserved because handwriting, diagrams and some degraded question numbers cannot safely be flattened into a single inferred sequence. Original page images remain attached and authoritative. UNIVERSITY EXAMINATIONS 2013/2014 YEAR ONE EXAMINATIONS FOR THE DEGREE OF BACHELOR OF MEDICINE, BACHELOR OF SURGERY, BACHELOR OF PHARMACY AND BACHELOR OF : DENTAL SURGERY : HBC 100/UPC 100/VBC 100: BIOCHEMISTRY DATE: AUGUST 5, 2014 TIME: 9.00 A.M. - 12.00 NOON SECTION A (30 MARKS): Attempt any THREE Questions. l. The Henderson — Hasselbalch equation is important in the calculation of a pH of a buffer q Pp solution. (a) With a specific, physiological example, explain the term “buffer solution”. (2 Marks) (b) Derive the Henderson Hasselbalch equation using a hypothetical: weak acid HA. (3 Marks) (c) How many grams of acetic acid (CH3CO;H) and sodium acetate are needed to make up to one litre of a 50 mm acetate buffer with a pH of 5.0. ka = 1.76 x 10°. 2 (a) State 4 functions of carbohydrates. (4 Marks): (b) Explain the basis of reduction tests as a means of identifying sugars in unknown solutions. 2 Marks) . Page 1 of 12 anr an “pd . A (c) Convert the following Fischer profection simuctu € [MO possible cide structures and state their full stereoisomeric names. (3 Marke . Ks) O C—— HO—-C— H HO—C—H H—C— OH — OH CH,0H GQ) What are enzymes? (3 Marks) (ii) Explain how enzymes work? 3 Marks P ( ) (iii) Where do enzymes come from and where do they go? (4 Marks) With full details, describe the enzymatic reactions that form a reversible link between the pentose phosphate pathway and the glycolytic pathway. (a) Suppose skeletal muscles were devoid of lactate dehydrogenase, could it carry out strenuous activity? Explain in detail? (b) People with beriberi, a disease caused by thiamine deficiency have elevated levels of blood pyruvate and a -ketoglutarate especially after consuming a meal rich in slucose. Write a detailed account on the biochemical basis of this elevation. Page 2 of 12 HON B 30 MARKS re St estions in the spaces provided ate o: iq . Me amino acid derivative ang , One function of the following amino acids. Asians [chums mo acid derivative Biological function frouce LMenionne Give the name and the general structure of a functional group that confers the following characteristics to organic molecules (biomolecules). Functional group General structure i Pleasant smell to fruits. Gives onion a pungent smell. Important in the manufacture of anaesthetics Page 3 of 1 rF Some enzymes require cofactors for their activities. Fill in the empty boxes in ‘\ following table. j COFACTOR ENZYME a. Coenzyme Flavin pyrophosphate monoamine oxidase Nicotineamide adenine Dinucleotide Pyridoxal phosphate t~—‘SY AcetylCoA carboxylase Zinc ees eee " Vitamin A is required for production of rhodopsin, thus too little of it can lead to and too much make you think you have tumor. Vitamin C is required for the production of the protein of connective tissue known as ; Vitamin C is also an and protects system, helping fight infections and reduces reactions. Too little of vitamin C can cause . Too much of vitamin C ( 1000 meg) may cause upset of , diarrhea or eee Too litle of vitamin Dcanecause weak bones (rickets) in children. (a) nee is necessary to . a fatty acid. Thisinvolves ofthe group of a fatty acid with the group of coenzyme A and where all subsequent intermediates of the fattyacidare of coenzyme A. Subsequent removal of 2-carbon fragments is catalysed by a a ——————— wa enzyme respectively. Page 4 of 12 (a) Gluconeogenesis is an exnensiy: reactions that provide e RENSIVe process. Name the enzymes that catalyse the (i) nergy for the conversion of lactate to glucose. 1 ee Gi) a (ait) a (b) Fill in the b ank boxes. The arrow denotes a one-step enzymatic reaction. == a ee Page 5 of 12 ‘ i ayers h ne . a — Sal a ~ 2 AN o wo q ™“ SECTION C (40 MARKS): MULTIPLE CHOICE QUESTIONS 4 \ For each statement, choose the most suitable answer from the 5 choices (A-E) and mary ‘X’ in the appropriate box in the answer sheet provided. Marks will not be awarded wher, more than one box is marked for each question. : 1. The following statement are true of hydrogen bond, except: (a) Hydrogen bonds account for the anomalously high boiling point of Wat (b) In liquid water, the average water molecule forms hydrogen bonds with three to four other water molecules. (c) Individual hydrogen bonds are much weaker than covalent bonds aa arog! i , (d) Individual hydrogen bonds in liquid water exists for many seconds and sometimes for minutes (e) The strength of hydrogen bond depends on the linearity of the three atoms involved in the bond 2. Dissolved solutes alter some physical properties of the solvent water because they change the: (a) Concentration of the water (b) Hydro