{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

BIBC 102 FInal Scheffler

BIBC 102 FInal Scheffler - METABOLIC BIOCHEMISTRY BlBC102...

Info icon This preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: METABOLIC BIOCHEMISTRY BlBC102 Fal12007 lmmo E. Scheffler FINAL EXAM All answers are to be written into the Blue Book. Leave the first inside page blank for scoring. There are 10 questions. Make sure that each answer is clearly identified with the question number at the top or left side of the page. Consider the statement on the back of the Blue Book; fill it out and sign it if you want to have your exam returned in the hallway outside of 3234 Bonner Hall. -H(:\'. 5}}ch tau/ll Like a drug (12.1! 1mm? ‘2', n lvc‘fh'l‘ (I! u'nrr/viu'q Tl '. won/ll”? val/7" ***~k***3!**************~k************~k***********************‘k******~k*********************** QUESTION 1 a) (3 min) Gluconeogenesis must use "bypass reactions“ to circumvent three reactions in the glycolytic pathway that are highly exergonic and essentially irreversible. Reactions carried out by which three of the enzymes listed must be bypassed in the gluconeogenic pathway? (1) Hexokinase. (WWWSC. (3) Phosphofructokinase-l . (4) Pyruvate kinase ( isomerase 0 1,2,3 0 1.2.4 0 1.4.5 ($1.14 4—47—374— b) (2 min) Which of the following statements about gluconeogenesis in animal cells is true? A) A rise in the cellular level of fructose—Mosphate stimulates the rate of gluconeogenesis. B) An animal fed a large exce fat in e die ill convert any fat not needed for energy production into glycogen to be stored f ate use. The conversion of fructose l,6-bisphosphate to fructose 6-phosphate is no! catalyzed by phosphofi'uctokinase-l, the enzyme involved in glycolysis. D) The conversion of g ose 6-phosphate to glucose is catalyzed by hexokinase. the same enzyme involved in glycoly IS. E) The conversion ofphosphoeno'lvaate to 2-phosphoglycerate occurs in two steps. including a carbox lation. , y “(L/Z, L c) (6 min) Under what circumstances does the bifunctional protein phosphofructokinase-Z/fructose 2.6- C M - bisphosphatase (PFK-Z/FBPase—Z) become phosphorylated. and what are the consequences of its ' phosphorylation to the glycolytic and gluconeogenic pathways? 9 5 4 V I 1 c, v 49 0 . i #0 _ C a 1A , 'c' "* + ’f " ’ i Q” i QUESTION 2 #1 ' ‘0 5’ a) (4 min) Acetyl-CoA labeled with HC in both of its acetate carbon atoms is incubated with unlabeled oxaloacetate and a crude tissue preparation capable of carrying out the reactions of the citric acid cycle. The a-ketoglutarate dehydrogenase can be inhibited with a specific inhibitor (e. g. arsenite) such that a-ketoglutarate accumulates. Show the structure of this compound and indicate all the carbons In this compound that would be radioactive (”C). b) (4 min) Malonate is a competitive inhibitor of succinate dehydrogenase. lf malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate. which of the following compounds would you expect to decrease in concentration? W B) F umarate Clencitcate We Ei/Saafiate c) (6 min) The two moles of C03 produced in the first turn of the citric acid cycle have their origin in the: A) carboxyl and methylenec ons of oxaloacetate B) carboxyl group of acetate an a ca yl group of oxaloacetate. C) carboxyl group of acetate and the group of oxaloacetate. D) two carbon atoms>Ka cetate. ® two carboxyl groups derived from oxaloacetate. [1f your answer is not correct (you are not sure) you can get partial credit by “showing" your thinking] d) (2 min) The reaction of the citric acid cycle that produces an ATP equivalent (in the form of GTP) by substrate level phosphorylation is the conversion of: A) citrat\o isocitrate B) fumanke to malate. C) mal to oxaloacetate. D) sud te to fumarate. @uccinyl-COA to succinate. e) (5 min)The conversion of 1 mol of pyruvate to 3 mol of C02 via pyruvate dehydrogenase and the citric acid cycle also yields mol of NADH. mol of FADHZ. and mol of ATP (or GTP). A)2: 2:2 B)3; 1:1 C)3;2;0 D)4: |:1 E)4;2;1 l) (4 min)The citric acid cycle is frequently described as the major pathway of aerobic catabolism. which means that it is an oxygen-dependent degradative process. However, none of the reactions of the cycle directly involves oxygen as a reactant. Why is the pathway oxygen-dependent? QUESTION 3 a) (2 min) During seed germination, the glyoxylate pathway is important to plants because it enables them to: A) carry out the net synLWf glucose from acetyl-CoA. B) form acetyl-C fro malate. @et rid of iso itrate formed from the aconitase reaction. 0 btain glyoxylate for chole I biosynthesis. E) obtain glyoxylate for pyrin$e synthesis. b) (4 min) A function of the glyoxylate cycle, in conjunction with the citric acid cycle, is to accomplish the: net conversion of lipid bohydrate. (33$ net synthesis of four-ca bon dicarboxylic acids from acetyl-CoA. D) net synthesis of long-chain fatty acids ' m citric acid cycle intermediates. E) both B and C are correct A) complete oxidation of acegl-COA to 7 plus reduced coenzymes. QUESTION 4 a) (6 min) Describe two possible sources/pathways for the production of acetyl-CoA in animals (name of pathway only). Where is the acetyl CoA produced? b) (6 min) Describe three pathways (name of end product only) that use acetyl-CoA as a starting material QUESTION 5 Several reactions in the citric acid cycle (Krebs cycle) are similar to reactions in the B—oxidation of fatty acids in mitochondria. a) (12 min) Show the starting material and intermediates for one cycle of fatty acid oxidation and give the corresponding sequence in the Krebs cycle with the names of the compounds only. \\b) (4 min) Name the co-factors involved in each of the relevant oxidation-reduction reactions QUESTION 6 The light-driven electron transport in chloroplasts drives the production of oxygen. the reduction of NADP+. and indirectly the synthesis of ATP. a) (3 min) Draw a schematic diagram to show where in the chloroplast this electron transport takes place b) (2 min) Show/name the compartment where ATP and NADPH are produced c) (l 0 min) Draw the schematic Z scheme for the light reactions, labeling all the essential components d) (10 min) How does the chemi-osmotic hypothesis of P. Mitchell apply to ATP synthesis in chloroplasts. A highly schematic diagram will be very useful for the explanation. QUESTION 7 The dark reactions in photosynthesis use the ATP and NADPH produced by the light reactions to fix C02 and to produce carbohydrate (hexoses). a) (8 min) Show with structural formulae the C02 fixation reaction by the enzyme "rubisco" (substrates and products) b) (5 min) What happens when oxygen participates in place of C02? c) (8 min) Part of the Calvin cycle includes the reactions used in gluconeogenesis; without explicit formulae, but with the names of the compounds. describe the starting intermediate and the final three- carbon intermediate(s) for this segment of the pathway. What co-factors are needed to drive these reactions? ‘ “ d) (6 min) Some of the three-carbon intermediates have to converted to the five carbon intermediate needed for C02 fixation; the reactions include two transketolase reactions: illustrate one of these with structural formulae for substrates and products. e) (6 min) Light regulates the activity of several enzymes involved in the Calvin cycle. Illustrate the mechanism with a very schematic diagram QUESTION 8 a) (6 min) Draw the complete structural formula for a fatty acyl cholesterol ester. b) (8 min) HMG-CoA reductase is the target for several related drugs (e.g. Zocor) widely advertised and used in our society. Give the structural formulae for the substrate of this enzyme and explain briefly the rationale for using these drugs. c) (10 min) The substrate for HMG-CoA reductase is also the intermediate for the synthesis of an important group of compounds. the ketone bodies. Name and give structural formulae for the ketone bodies and explain briefly why and when they become important. QUEsn0N9 a) (4 min) Transamination reactions are important in the metabolism of amino acids. Illustrate the reaction with a general example b) (4 min) Name the cofactor for these reactions and give its structural formula c) (2 min) The reaction depends on the formation of an intermediate; what is its generic name? QUESTION 10 The urea cycle serves to produce urea. for the secretion of excess nitrogen in mammals and other organisms. a) (4 min) Draw the structure of urea; where do the nitrogens. carbon and oxygen come from? b) (6 min) The compound entering the urea cycle is carbamoyl-phosphate; describe its synthesis c) (10 min) Intermediates relevant in the urea cycle are the following: carbamoyl-phosphate. citrulline. arginino-succinate. ornithine. arginine. fumarate. and urea. Draw the cycle with the intermediates in the correct order and show what enters and exits the cycle. THEEND ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern