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BCHM2072/2972 Semester 2, 2005 Page 1 ASSIGNMENT 3, WEEK 7 This assignment is due in the box at the front of the lecture theatre by no later than 10.10 am on Wednesday 14th September. Late assignments, assignments not answered on the grid provided, or assignments not covered by a plagiarism statement (universal or individual) will not be marked. Remember, submission of assignments is entirely voluntary. Enter your SID and answer all questions by filling in the relevant circles on the grid provided. Use the options A-F to answer questions 1-3 A. B. C. D. E. F. Every even numbered carbon Every even numbered carbon except C2 Every even numbered carbon except C16 None of the carbons Every odd numbered carbon except C3 Every odd numbered carbon except C15 If palmitoyl CoA (pictured below) was made from 15 16 13 14 11 12 9 7 10 8 14C malonyl CoA 5 6 CO 3 4 SCoA 2 which pattern of labeling would be observed if the malonyl CoA used was labeled: 1. 2. 3. at C1 (the terminal carboxylic acid end) at C2 (the –CH2- in the middle) at C3 (the carbon in a thioester with CoA) To help you, here is a picture of malonyl CoA with the carbon atoms numbered. 1 HOOC H2 C 3 2 CO SCoA BCHM2072/2972 Semester 2, 2005 4. Page 2 Which of the following (A-F) is not a fate of cholesterol in mammalian tissues? (1 mark) A. Bile salts B. Cell membranes C. Estrogen & Testosterone D. Incorporation into VLDL E. CO2 F. Cholesterol esters 5. Which of the following (A-E) would an inhibitor of lipoprotein lipase directly prevent? (1 mark) A. The uptake of dietary fat in the intestine B. The conversion from VLDLs to LDLs C. The release of fatty acids from adipose tissue D. The uptake of dietary cholesterol by cells from LDLs E. The formation of lipoproteins 6. Which of the following changes (A-F) would directly decrease the activity in vivo of Acetyl CoA Carboxylase? (1 mark) A. An increase in insulin B. An increase in acetyl CoA C. An increase in palmitoyl CoA D. An increase in cytoplasmic [citrate] E. An increase in G6P F. An increase in HCO3- The data in the table below relates to questions 7 – 8 (1 mark each). Individual A B C D E Endogenous HMG CoA reductase activity # LDL receptors on cell surface HDL:LDL High High High Low Low Low High Low Low Low High High High Low High Based on the data, which of the individuals (A-E) has the: BCHM2072/2972 Semester 2, 2005 7. Highest risk of coronary heart disease 8. Lowest risk of coronary heart disease Page 3 The following information relates to questions 9 -18 (1 mark each). The oxidation of glucose is often summarised as the balanced equation: C6H12O6 + 6 O2 + 32 ADP + 32 P 6CO2 + 6 H2O + 32 ATP Of course, this misses out all the juicy steps of glucose transport, glycolysis, PDH, Krebs cycle, electron transport, F1F0ATPase, etc. However, it does encapsulate the overall point and function of the pathway. The overall equation is actually made up of lots of ‘partial’ equations that are added together. OK, So that was just an example. The overall balanced equation for the synthesis of fatty acids from glucose (lipogenesis) can be written (for the 16carbon fatty acid, palmitate) as: 9 glucose + 8 O2 2 palmitate + 22CO2 + 22 H2O Hint : At this stage you will find it very useful to draw out the scheme of lipogenesis from glucose (eg as in the final slide for Lecture 12) to answer these questions. Do not think that you have to derive the equation. However, you should reflect on all the juicy steps that actually have to occur to make lipogenesis happen. 9. The lipogenesis equation does not mention ATP because: A B C D E 10. ATP is not produced or consumed in lipogenesis During lipogenesis as much ATP is produced as is consumed The equation refers to a section of lipogenesis in which ATP is not used The equation shows only the anabolic arm of lipogenesis The equation shows only the cytosolic part of the pathway In compiling this overall lipogenesis equation, which process would you NOT take into account? A B C D E The fatty acyl synthase reactions Esterification of fatty Acyl-CoAs The fate of 5-carbon sugar phosphates in the pentose phosphate pathway The reactions of glycolysis The trapping of glucose BCHM2072/2972 Semester 2, 2005 11. Why is oxygen required in this lipogenesis equation? A B C D E 12. Page 4 To provide reducing equivalents To mop up excess NADPH Oxygen gas isn't used in the grand scheme, it's just required here to make a balanced equation It reflects the consumption of oxygen at the end of the electron transport chain To enable carbon dioxide formation There is carbon dioxide release at several steps during lipogenesis. At which of the following steps is a carbon dioxide molecule released? A B C D E Pyruvate dehydrogenase Aldolase Acetyl CoA carboxylase Glucose 6-phosphate dehydrogenase ATP-citrate lyase 13. Which particular segment of the overall lipogenesis pathway does NOT involve NET release of carbon dioxide? A B C D E 14. As malonyl CoA is incorporated into the growing fatty acyl chain As pyruvate molecules are made into acetyl-CoA As acetyl-CoA molecules are oxidised in the Krebs cycle As ribulose 5-phosphate is produced in the pentose phosphate pathway As acetyl-CoA is made into malonyl-CoA The energetic values for glucose and fatty acids are 16 kJ/g and 37 kJ/g respectively. The molecular weights of glucose and fatty acids are 180 and 256 respectively. There is 'energy' in the glucose and 'energy' in the fatty acids. Which statement best describes the 'efficiency' of lipogenesis? A B C D E 2880 kJ of energy in glucose ends up as 9472 kJ fatty acids 27% of the energy in the glucose is lost as it is converted into fatty acids The fatty acids products contain about half as much energy as the glucose substrate A total energy of 1620 kJ in carbohydrate becomes just 512 kJ in the final fatty acid products The total energy of the fatty acid products is about twice that of the total energy of the glucose substrate BCHM2072/2972 Semester 2, 2005 15. Which description best describes the respiratory quotient of someone who has consumed a carbohydrate meal and is actively performing lipogenesis? A B C D E 16. about 0.7 over 1 less than 0.7 exactly 1 exactly 2.75 How would you adapt the lipogenesis equation so that it describes the conversion of glucose to fat? A B C D E 17. Page 5 At least three palmitates would be needed on the right hand side of the equation, so more glucoses would be needed on the left hand side Fewer glucoses would be needed on the left hand side of the equation because now glycerol would appear on the right hand side The equation would be exactly the same Fewer glucoses would be needed on the left hand side of the equation because glycerol is more reduced than glucose It would not be possible to produce a balanced equation for fat synthesis You have been asked to write the overall balanced equation for glycogen synthesis from glucose. It will have a similar form to the lipogenesis equation above ie: some amount of glucose (X) + one or more things some amount of glucose residues in glycogen + one or more other things What would best describe the sort of equation you'd come up with: A B C D E (X) Glucose + some amount of ATP (X) glucose in glycogen + some amount of ADP (X) Glucose + some amount of O2 (X) glucose in glycogen + some amount of CO2 (X) Glucose + some amount of UTP (X) glucose in glycogen + some amount of UDP (X) Glucose + some amount of O2 less than (X) glucose in glycogen + some amount of carbon dioxide (X) Glucose + some amount of UTP less than (X) glucose in glycogen + some amount of UDP BCHM2072/2972 Semester 2, 2005 18. Page 6 Which process would NOT be useful to take into account in making your balanced glycogenesis equation? A B C D E UDP-glucose + glycogen gluocse in glycogen + UDP UDP + ATP UTP + ADP UTP + glucose 1-phosphate UDP-glucose + 2 phosphate glucose 6-phosphate + NADP NADPH + 6-phosphgluconolactone glucose + 6O2 + 32ADP + 32 phosphate 6CO2 + 6H2O + 32ATP