MCMP 208 Exam III Key - 1 Examination III Key MCMP 208 – Biochemistry for Pharmaceutical Sciences I April 8, 2015 Correct answers in multiple choice questions are indicated in RED and underlined. Correct answers to essay questions are indicated in RED in comic book font. In some cases and explanation is provided in BLUE/BLUE MATCHING. For problems 1 to 3, a set of numbered answers is provided immediately below. For each problem, select from the list of answers the single choice that best matches the item described in the problem. Mark that answer on your answer sheet. An answer may be used more than once or not at all. [3 points each] Cholesterol Cholic acid Prostaglandin Leukotriene Saturated fatty acid ω-3 fatty acid ω-6 fatty acid Sphingomyelin Phosphatidylserine Phosphatidylcholine 1. R and R′: hydrocarbon chains 2. 3. MCMP 208 Exam III Key - 2 MULTIPLE CHOICE. For problems 4 to 23, select from the list immediately following each question the single most correct choice to complete the statement, solve the problem, or answer the question. Mark that answer on your answer sheet. [3 points each] 4. What are the constituent(s) of the core of lipoproteins? Apolipoprotein Amphipathic Triacylglycerol Hydrophobic Phospholipids Amphipathic Cholesterol Amphipathic Cholesterol ester Hydrophobic and and The core of lipoproteins is composed of insoluble hydrophobic molecules, while the shell of lipoproteins is composed of amphipathic molecules. 5. Which of the following statements is INCORRECT about biological membranes? Membranes serve as a barrier to ionic and polar substances. Proteins and lipids can diffuse and interact in the membrane. Tissue and various cell membranes have a distinctive lipid composition. Unsaturated fatty acyl groups decreases the fluidity of membranes. The transverse movement (flip-flop) of membrane lipids is catalyzed by enzymes. Unsaturated fatty acyl groups make poor packing, which increases the fluidity of membranes. 6. Transmembrane helices of integral membrane proteins are composed of mostly ____________ residues. small hydrophobic polar charged branched aromatic Transmembrane helices of integral membrane proteins contact the hydrophobic layer of the membrane. The hydropathy plot of the amino acid sequence of an integral membrane protein is used to identify transmembrane helices. 7. Which of the following is a transporter with a uniport mechanism? Glucose transporter Uniport ATP–ADP transporter Antiport Na+/K+-ATPase Antiport Na+/glucose cotransporter Symport Acetylcholine receptor Not a transporter Voltage-gated Na+ channel Not a transporter MCMP 208 Exam III Key - 3 8. Which of the following is a secondary active transporter? Glucose transporter Passive ATP–ADP transporter Passive Na+/K+-ATPase Primary active Na+/glucose cotransporter Secondary active Acetylcholine receptor Not a transporter Voltage-gated Na+ channel Not a transporter 9. Which organ or tissue is the greatest contributor of lipids into the blood circulation during times of prolonged fasting? liver brain intestines adipose mammary muscle 10. Lipoproteins released into the blood differ in many ways from the lipoprotein remnants that are endocytosed from the blood for recycling of their components. Of these differences, the greatest change(s) is(are) that remnants have lost most of their apolipoproteins cholesterol and cholesterol esters phospholipids phospholipids, cholesterol and cholesteryl esters phospholipids and apolipoproteins phospholipids and triacylglycerol triacyglycerol, cholesterol and cholesteryl esters The PL and protein are the “packaging” on the surface so the droplet can travel in the circulation, but they are not consumed by the rest of the body. While some proteins are lost during the depletion of TG and cholesterol because the particle diameter decreases, the loss of protein is much smaller than the loss of TG, cholesterol, and cholesterol esters. 11. Before β-oxidation of palmitate can occur in the mitochondrial matrix, it must be converted to palmitoyl-CoA outside the mitochondrial matrix palmitoyl-CoA inside the mitochondrial matrix palmitoyl-ACP outside the mitochondrial matrix pallmitoyl-ACP inside the mitochondrial matrix palmitoyl-carnitine outside the mitochondrial matrix palmitoyl-carnitine inside the mitochondrial matrix palmitoyl-CoA then palmitoyl-carnitine outside the mitochondrial matrix, then palmitoyl-CoA inside the mitochondrial matrix palmitoyl-CoA then palmitoyl-carnitine inside the mitochondrial matrix, then palmitoyl-CoA outside the mitochondrial matrix palmityl-pyrophosphate outside the mitochondrial matrix palmityl-pyrophosphate inside the mitochondrial matrix MCMP 208 Exam III Key - 4 12. All acylation of alcohol or amino groups occurring during the biosynthesis of triglycerides, phospholipids, and sphingolipids involve transfer of acyl groups from acyl carrier protein serum albumin apolipoproteins lipid droplets coenzyme A pyrophosphate CDP pyridoxal phosphate 13. The molecule with the structure shown to the right is synthesized malonoyl-CoA in order to serve as the starting molecule for extension into fatty acids by addition of subsequent acetate units in order to make it easier to produce a carbanion of acetate during fatty acid synthesis in order to make condensation into ketone bodies more energetically favorable during glyeroneogenesis in order to make sphinganine in order to shuttle acetate units out of the mitochondria during catabolism of odd chain length and branched fatty acids 14. The olefin bonds in fatty acids which are biosynthesized entirely in human cells are created during the oligomerization process and simply left in the fatty acid are created during the oligomerization process by condensing an unsaturated 4-carbon acid are added in the endoplasmic reticulum after the oligomerization process are added in the peroxisomes before the oligomerization process are added only during the catabolism of fatty acids include both cis and trans configurations, depending on the specific fatty acid length None of the above are correct. 15. In mammals, including humans, fatty acid biosynthesis in lactating mammary tissue differs from fatty acid synthesis occurring in other tissues in that fatty acid synthesis in the lactating mammary gland occurs exclusively in the endoplasmic reticulum sometimes occurs in the mitochondria frequently produces fatty acids longer than 16 carbons frequently produces fatty acids shorter than 16 carbons frequently produces fatty acids with odd numbers of carbons frequently produces branched chain fatty acids MCMP 208 Exam III Key - 5 16. Hormonal regulation of the biosynthesis and catabolism of fatty acids occurs primarily at acetyl coenzyme A carboxylase acyl coenzyme A ligase hormone sensitive lipase lipoprotein lipase carnitine acyl transferase fatty acid synthase pyruvate dehydrogenase ACC not only is where fatty acid synthesis is regulated, but because mitochondrial FA oxidation is regulated by Acylcarnitine transferase, and it is inhibited by malonyl-CoA, ACC activity also regulates mitochondrial fatty acid oxidation. 17. Nitrogenous bisphosphonates are intermediates in the biosynthesis of glycolipid intermediates in the biosynthesis of isoprenoids drugs used to treat hypercholesterolemia drugs used to treat obesity drugs that block protein prenylation drugs that block mono-oxygenases 18. A person who has a positive nitrogen balance likely is suffering from protein malnutrition has recently suffered from trauma or severe burns or has had major surgery has difficulty absorbing amino acids from ingested foods is growing, pregnant, or lactating None of the above are correct. 19. Neutral (zwiterionic) phosphoglycerolipids differ in their synthesis from some acidic phosphoglycerolipids in that neutral phosphoglycerolipids are nearly always made by head group transfer to DAG involving the CDP-activated head group acylation of the lysophospholipid addition of the head group to phosphatidic acid head group exchange with a molecule of phospholipid head group transfer to CDP-DAG from the phosphorylated head group 20. Methionine is an essential amino acid that is also glucogenic It’s carbons are converted to proprionyl-CoA a non-essential amino acid that is also glucogenic is a semi-essential amino acid that is also glucogenic an essential amino acid that is also ketogenic a non-essential amino acid that is also ketogenic is a semi-essential amino acid that is also ketogenic an essential amino acid that is both ketogenic and glucogenic a non-essential amino acid that is both ketogenic and glucogenic is a semi-essential amino acid that is both ketogenic and glucogenic MCMP 208 Exam III Key - 6 21. Homocysteine is converted into cysteine by removal of a methylene group from homocysteine converted into cysteine by addition of a methylene group to homocysteine converted into cystathionine by the addition of serine to homocysteine made from cystathionine by removal of a cysteine from homocysteine made from methionine by the addition of a cysteine to methionine made from methionine by the addition of a serine to methionine made from methionine by the addition of a methyl group to methionine used to make one-carbon groups that are bound to THF used to make phosphatidylcholine from phosphatidyethanolamine 22. The proteasome is a supramolecular structure responsible for the multistep process of fatty acid synthesis involved in membrane-vessicle fusion during membrane remodeling responsible for degrading all molecules endocytosed by cells responsible for ATP-dependent protein degradation responsible for determining the half-life of all proteins responsible for the synthesis and initial post-translational modifications to proteins involved in movement of proteins into and out of the cell nucleus 23. L-α-amino acids that serve as intermediates in the biosynthesis of arginine from the first non-nitrogenous molecule in its biosynthetic pathway are glutamate, glutamine, and aspartate glutamate, ornithine, and aspartate glutamate, ornithine, citrulline, and argininosuccinate glutamate, proline, ornithine, citrulline, and argininosuccinate glutamate, ornithine, citrulline, asparatate, and argininosuccinate glutamate, proline, and aspartate An intermediate is a molecule made in the pathway that is also consumed in the pathway, with both of those events happening after the starting material and before production of the final product. Aspartate is consumed, but not produced by the arginine biosynthesis pathway, so is not an intermediate (it is an input to the reactions of the pathway, just as are ATP, bicarbonate, and water.) ESSAY PROBLEMS. Write your answers to problems 24 to 30 in the space immediately below each problem (or in the blanks for problem 25). 24. [3 points] Triacylglycerol is the main constituent of both butter and olive oil. However, butter is solid, and olive oil is liquid at room temperature. Explain briefly the chemical basis of this difference. Olive oil has a higher content of unsaturated fatty acids than butter. Unsaturated fatty acids makes poor packing compared with saturated fatty acids. Poor packing decreases the melting point. MCMP 208 Exam III Key - 7 25. [3 points] The action of ATP–ADP transporter is shown below. Fill the blanks in the following questions. ADP3- ADP3- ATP4- ATP4- (a) [2 points] When ATP and ADP are exchanged in the direction indicated above, the net charge of ______-1_______ moves from Side _____2____ to Side _____1_____. (b) [1 points] When Side ____2______ has a more negative membrane potential, the exchange in the direction indicated above is more favorable. 26. [3 points] Explain briefly the molecular origin of cystic fibrosis. Patients with cystic fibrosis have mutations in a membrane channel. The mutations interfere with the folding of the channel protein, and the amount of the active channel is insufficient in the patients. 27. [6 points] There are six entry points into metabolism for the catabolism of amino acids. Each of these entry points is either glucogenic or ketogenic, but not both. List these metabolic entry points. Also, for each entry point, indicate if that entry point is for glucogenic amino acids (or fragments of amino acids) or if it is for ketogenic for amino acids (or fragments of amino acids) by placing the word (glucogenic or ketogenic) next to the entry point in your answer. α-ketoglutarate oxaloacetate pyruvate fumarate succinyl-CoA glucogenic glucogenic glucogenic glucogenic glucogenic acetyl-CoA ketogenic MCMP 208 Exam III Key - 8 28. [5 points] Of the 20 L-α-amino acids used for protein synthesis, list those that are made directly from the carbons in α-ketoglutarate (without having to go through any other pathways in intermediary or carbohydrate metabolism.) For each of the amino acids you list, indicate which category the synthetic pathway length belongs in, choosing only from these three categories of length (in terms of number of steps catalyzed by different enzymes): “1 or 2 steps”; “3 or 4 steps”; “more than 4 steps”. Glutamate Glutamine Proline Arginine 1 or 2 steps 1 or 2 steps Either “3 or 4 steps” or “more than 4 steps” are allowed as correct. This is because the cyclization reaction (Schiff base formation) is likely to be spontaneous and not catalyzed by an enzyme, hence only 4 enzymes are needed from α-KG, though it may take 5 reactions.) more than 4 steps 29. [6 points] Complex lipids can be described as oligomers of oligomers. When this is concept is applied to cholesterol, it is actually an oligomer of an oligomer of an oligomer. a. [2 points] What is the name of the metabolite produced by the first stage of oligomerization (before it is further modified for use in the next stage)? 3-Hydroxy-3-methylglutaryl-CoA also acceptable are HMG-CoA and HMG-coenzyme-A HMG-CoA is made from three molecules of acetyl-CoA. Even though the two condensations are not identical types of condensations, this is still an oligomerization b. [2 points] What is the name of the metabolite produced by the second stage of oligomerization? Farnesy-pyrophosphate This is made from three isoprenes (one dimethylallyl-PP and two isopentenyl-PPs), added in two identical condensation reactions. c. [2 points] What is the name of the metabolite produced by the third stage of oligomerization (before it is further modified)? Squalene This is made from two farnesyl-PP. 30. [5 points] This question is about ketone bodies. a. [2 points] What are the names OR structures of the ketone body molecules? Acetoacetate β-hydroxybutyrate Note that either the correct structure or the name of the molecule will be awarded credit for each of the two keto bodies. Also, structures of either the acid or carboxylate forms will be considered correct as well as the acid or conjugate base names. MCMP 208 Exam III Key - 9 b. [1 point] In what organ/tissue are ketone bodies synthesized? Liver or hepatocytes c. [1 point] When are ketone bodies synthesized? During prolonged fasting d. [1 point] Why are ketone bodies synthesized? To reduce consumption of blood glucose by the brain. Ultimately, this reduced utilization of blood glucose spares body protein which must be broken down for use by the liver to make blood glucose.
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