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SBS017 Basic Biochemistry May examination 2012 SECTION C Answer question 4 OR question 5 in this booklet. Do not use additional paper or booklets. Do not take the booklet from the examination room. Student number: …………………………………………………………………. Desk number: …………………………………………………………………. Please fill in BOTH these boxes with the numbers of the questions you answered: SECTION B QUESTION ANSWERED SECTION C QUESTION ANSWERED Page 2 Section C –Short Answer questions - 33% Answer question 4 OR question 5 in this booklet. Each question is worth 33 marks. Question 4 A SBS017 – Section C Example Answer all parts Fill in the following blanks in these sentences with the candidate terms in boldface listed below. Note that not all the words are used. [1 mark each.] A ____________________________ reaction has a G (the change in freeenergy) that is negative in sign. A reaction of this kind can be used to drive one that is ____________________________ that is coupled to it in a series of reactions. The key molecule most used as the energy currency of biological systems is ________________. This energy carrier molecule contains two _____________________ bonds, and is an example of an activated carrier. The group this molecule carries is the ________________ group. Other activated carriers include ________________ which carries carbon dioxide, and ________________ which is a carrier of electrons in membrane proteins. Humans obtain their energy via the oxidation of foodstuffs and as such we are ________________. There are three stages in this overall oxidation process. The first takes Fats, Sugars and Proteins and breaks these large molecules into smaller ones. These are further processed to generate a common small molecule which is ________________. It is this molecule that links into the final stage, that of ____________________ and oxidative phosphorylation. Candidate terms: phototrophs; cysteine; phosphoryl; sulphur; disulphide; FADH2; the Calvin Cycle; methionine; biotin; thermodynamically favourable; phosphoanhydride; acetyl-CoA; chemotrophs; base pairs; guanine; tetrahydrofolate; thermodynamically unfavourable; the Citric Acid Cycle; ATP Continued on next page SBS017 – Section C Example B Page 3 Indicate TRUE or FALSE to each of these statements (2 mark each) i) Glucose is a five carbon containing sugar _______________________________ ii) Glucose-4-phosphate is a molecule used in glycolysis _______________________________ iii) 1,3-Bisphosphoglycerate is converted to 3-phosphoglycerate by the enzyme Phosphoglycerate kinase _______________________________ iv) Aldolase and Triosphosphate isomerase share a common TIM barrel threedimensional structure _______________________________ v) Pyruvate is the last molecule produced in the glycolysis pathway _______________________________ C) Draw the structures of the molecules indicated below i) Glucose as a ring structure (5 marks) Continued on next page SBS017 – Section C Example Page 4 ii) Glyceraldehyde 3-phosphate (4 marks) iii) Pyruvate (4 marks) SBS017 – Section C Example Question 5 A Page 5 Answer all parts The citric acid cycle is also known as: (1 mark) The Krebs cycle or __________________________________________ B Fill in the blanks. (8 marks) Prior to the citric acid cycle the enzyme complex Pyruvate dehydrogenase performs the reaction: Pyruvate + __________________ + _______________________ __________________ + CO2 + _______________________ C Fill in the blanks. (4 marks) The enzyme Citrate synthase performs a condensation reaction: ____________________ + oxaloacetate + H2O _____________________ D + Citrate Draw the following molecules. i) Citrate (5 marks) Continued on next page SBS017 – Section C Example Page 6 ii) Oxaloacetate (5 marks) E Fill in the blanks from the list of choices given below. (10 marks). In the citric acid cycle the enzyme _______________________converts _______________________to succinyl-CoA. This enzyme process is one of two _______________________________ steps in the cycle the other being the previous step in the cycle carried out by the enzyme ___________________________. In each of these processes the coenzyme ________________________ is converted to ______________________. The enzyme ____________________________ converts succinate to the molecule _______________________. This molecule is then hydrated by the addition of water to form malate by the enzyme _________________. From this product by an ____________________ process we then arrive back at oxaloacetate. It is this molecule that is involved in the initial processes of the citric acid cycle and proves that the process is indeed cyclic. Candidate terms: NADH; alpha-ketoglutarate dehydrogenase; transcarbamoylase; citrate synthase; oxidation; dehydrogenase; oxidative decarboxylation; dehydrogenase; fumarate; citrate; End of section C FADH2; FAD; CO2; NAD+; succinate chymotrypsin; dehydration; ornithine isocitrate alpha-ketoglutarate; argininosuccinate synthetase; fumarase; isocitrate