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Chem 153A Spring 2020 Final Exam June 7-9, 2020 Same things apply as Exam 1 and Exam 2 _________________________________________ ______________________________ ________ Signature Student ID Date ****NOTE: • This practice exam has been modified to only reflect questions on content you may see on your exam. • This exam is 2.5 times as long as yours will be. Question: 1 2 3 4 5 6 7 8 TOTAL Points: 16 3 13 12 10 20 9 25 108 Always assume physiological conditions UNLESS otherwise stated. Be sure to read all the questions carefully, and answer the question that is asked. For full credit show all your work. Always fully label axes on any graph, on this exam and in life. Answer questions as concisely as possible. The sentence limits include normal length sentences. Run-ons will be counted as 2 sentences. You do not have to use complete sentences. Abbreviations are acceptable for short answer questions.Chem153A Spring 2020 Final Exam Full Name:________________________________________ Page 2 of 7 UID:_______________________________ Lec: ________ Constants and values that may be necessary for the Exam: c ΔGo’ of ATP Hydrolysis = -30.5 kJ/mol ΔGcell of ATP Hydrolysis = -50 kJ/molChem153A Spring 2020 Final Exam Full Name:________________________________________ Page 3 of 7 UID:_______________________________ Lec: ________ 1.(16 pts) Identify the following compounds giving their full name and in 1 sentence describe the importance of their function in the cell. A Name: _Reduced Flavin mononucleotide__ Function: Electron carrier in Complex I of the ETC that connects NADH to metal ion carriers B Name: _(Reduced) or (dihydro)lipoamide__ Function: Prosthetic group for E2 of pyruvate dehydogenase complex that channels substrates within PDH (OR transfers the acetyl group to Coenzyme A) C Name: _Reduced Coenzyme Q__ Function: Lipophilic mobile electron carrier in the ETC (OR: carries electrons from complexes I or II to Complex III) D Name: __Adenosine Monophosphate___ Function: Allosteric regulator indicating low energy charge (OR activates catabolic pathways and inhibitsanabolic pathways).Chem153A Spring 2020 Final Exam Full Name:________________________________________ Page 4 of 7 UID:_______________________________ Lec: ________ 2). (3 pts) What determines the overall stability of the membrane? How might having shorter fatty acids in the membrane affect that stability? (2 Sentences MAX) • stability is determined by sum of all the non-covalent interactions that hold the membrane together. • fewer weak interactions can form between the fewer number of carbons (in the shorter fatty acid). • Thus the membrane would be less stable with shorter fatty acids. 3. (25 pts) The Enzyme Glutamine Synthetase has a Km of 8 mM for its substrate ammonia, which it binds cooperatively. It also binds an allosteric (non-competitive) inhibitor, CTP, with a Ki of 0.1 mM, but it does not bind CTP cooperatively. A). (2 pts) What is the definition of Km and what does it represent? Definition: the [substrate] required for the initial velocity to be ½ of the maximum velocity. Represents: the affinity of the enzyme for the substrate B). (2 pts) What is the definition of Ki and what does it represent? Definition: the [Inhibitor] required for half of the enzyme binding sites to be occupied Represents: The affinity of the enzyme for the inhibitor. C). (6 pts) Draw ligand binding curves for both the substrate and the inhibitor binding to the enzyme. D). (3 pts) What is the biochemical basis for the difference in the position of the curves along the X axis? Hint: it does NOT depend on shape (2 sentences MAX) The enzyme has a lower Kd for CTP than for ammonia. Thus it binds CTP tighter through overall stronger interactions. 00.10.20.30.40.50.60.70.80.910 5 10 15 20 25Fractional saturation (theta alone is not enough)[Ligand (OR Ammonia/CTP) (mM)*Substrate is not accepted as CTP is not a substrateAMMONIACTPChem153A Spring 2020 Final Exam Full Name:________________________________________ Page 5 of 7 UID:_______________________________ Lec: ________ 4. (12 pts) You are studying the use of glutamate as a potential source for glucose in cancer cells. You start with glutamate labeled on the alpha carbon. A). (4 pts) If the glutamate entered the TCA cycle as α-ketoglutarate show the labeling pattern and distribution on the first oxaloacetate formed. B). (2 pts) Describe the population of oxaloacetate your answer in part A represents. Half the OAA molecules are labeled on the carboxylic acid next to the carbonyl and half the OAA molecules are labeled on the other carboxylic acid. C). (2 pts) If this oxaloacetate were going through the TCA cycle where would you be able to find label after the next turn of the cycle? What would be the relative amounts in any molecules that contained label? All the label would be in carbon dioxide C). (4 pts) Oxaloacetate can also be directed through gluconeogenesis. If the oxaloacetate in part A were used to make glucose where would the label be found in the glucose: Carbons 3 and 4. Note: OAA → PEP the bottom carboxylic acid leaves (compare to pyruvate). Thus carbon 1 of PEP is labeled which corresponds to carbons 3 and 4 of glucose 5. (10 pts) An Acyl-phosphate (pictured below) is a type of high energy phosphate containing compound. A). (2 pts) What enzymes in the central metabolic pathway produce acyl-phosphates? Glyceraldehyde-3-phosphate and succinyl-CcoA Synthetase B). (2 pts) Ultimately, where does the energy to produce the acyl-phosphate come from? (5 words max) Oxidation of carbon. C). (6 pts) Briefly describe the mechanistic step that directly makes the acyl-phosphate. (2 sentences Max) The oxidation of the carbon forms a thioester, which is then nucleophillically attacked by an inorganic phosphate. This cleaves the thioester and attaches the phosphate to the molecule forming the acyl-phosphate. CCHO HCH2OP1,3-Bisphosphoglycerate(BPG)O OPRC OPOAcylphosphate("high energy")50% * 50% * * *Chem153A Spring 2020 Final Exam Full


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UCLA CHEM 153A - Practice Exam 3 Answer Key

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