2005exam2key

2005exam2key - BCH227 Name " Number b A, i i...

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Unformatted text preview: BCH227 Name " Number b A, i i EXAMINATION 2 BIOCHEMISTRY 227 November 2, 2005 Instructions: Write your name and number on each page of the examination. Answer questions in the space provided after each question. The number in parenthesis is the number of points for a given question. The examination is expected to take 50 minutes, but you will be given 60 minutes if you Wish. 1.5 05) 6(6) 7.(8) 8.02) 9.00) 10.(8) 11.02) 12(8) 13.0) 14.07) BCH227 ' Name i“ Number [For multiple choice, circle the correct answer.] (3) 1. The multi-drug resistant (MDR) transporters that remove anti—cancer drugs from cancerous cells operate: A) Via passive diffusion B) Using the K+ gradient C) Using the Na+ gradient \/ D) Using ATP hydrolysis E) Using the H+ gradient (3) 2. The following compound is not a cholesterol derivative \/A) Vitamin A B) Vitamin D C) Estradiol D) Testosterone E) Ouabain (3) 3. Membranes typically do not contain A) Phosphoglycerolipids B) Glycoproteins C) Cholesterol D) Beta-barrel proteins ‘x/ E) Glucose-6-phosphate (3) 4. From the abbreviated name of the compound Gal([31 —>4)Glc, we know that: v/ A) C-4 of glucose is joined to C-1 of galactose by a glycosidic bond. B) the compound is a D-enantiomer. C) the galactose residue is at the reducing end. D) the glucose is in its pyranose form. E) the glucose residue is the [3 anomer. (3) 5. Enzymes that catalyze the synthesis of long chain fatty acids in vertebrate cells: A) act as seven separate proteins. B) are encoded in mitochondrial genes. C) are localized in the mitochondrial matrix. D) are in a monomer of a polypeptide containing several distinct enzyme activities. \/E) are in a dimer of a polypeptide with several distinct enzyme activities. BCH227 Name k 26* ‘ Number (6) 6. This compound is the linear (open) form of fructose. T A) Is thi or L- fructose? (circle correct answer) HwC—OH émo B) Is this an aldose, or “ l HO—C—H . . . . l C) Sometimes the r1ng form of fructose 1s a furanose, and sometimes H“c"0H it is a yranose. To form a yranose rin , which 0 atom would 1 P P g H—CI—OH attack which C atom? (Draw an arrow from the O to the C) CH20H (8) 7. Passage of one glucose through glycolysis yields 2 pyruvates, 2 ATPs and 2 NADHs. Lactate dehydrogenase catalyzes the reduction of pyruvate by NADH, as shown. 0 0~ 0 O \xc/ NADH + H+ \c/ | NAD" I $=O HO—t‘i iattata CH3 dehydmgefiase CH3 Pyruvate L—Lactate A) Circle the H atom on lactate that was transferred directly from NADH. B) Under anaerobic conditions (in muscle, e.g.), glycolysis stops unless the above reaction takes place. Why? NQDH accumu\c.)"cs H E/UA’B‘FJ 4W5. Wfi'lwd “J‘Ide MW+) ghjcevtldekjc. 3' Wm... W cm h BCH227 Name r: ‘ Number (12) 8. Citrate synthase catalyzes the attack of acetyl-SCoA on the Carbonyl of oxaloacetate, in the first step of the reaction sequence that produces citrate. The enzyme helps stabilize a normally less stable form of the acetate moiety, one carbon of which acts as the nucleophile in the attack on oxaloacetate. A) Draw acetyl-SCoA B) indicate how it is converted to the intermediate C) what is this form of acetate called? C) Show how the intermediate attacks oxaloacetate (just use “SCoA” for coenzyme A in your answers). scoA —°‘\ 196°? Osc/ .._.._A c ‘L/ \ .‘_._— H “'9“ /C n ‘H L. eno‘b+e ‘ ks a - (w n‘ w Ac ‘5‘ 563A uf H+ 3 4mm“- o“ /5CaA C (6A \ ,_9?,,\C/S a“ “’0’ c9?— é, H f; é— C00, (22 I’ H7. <’ HO"l / ' \ H ‘.R_ , - Coo; $347. w wk. Oxaleml-de coo' BCH227 Name Number (10) 9. The first step in the conversion of alpha-keto glutarate to suc inyl-CoA is chemically the same as for the conversion of pyruvate to acetyl-CoA. Draw this step for alpha-keto glutarate (that is, draw the carbanion of TPP attacking alpha-keto glutarate, and draw the resulting addition compound). {‘9 r ‘ - f Rw§iCNS é - //C~ ;\/,\d; J H“ 09¢ — ’C...¢..\LC‘Ha COO M i 2 ’Ne C H ,_>——> R \/ I 7. C CH 1 9 l s," // \ S 3 CH7. _,. we; C”? \ , Q / I 600 K a L‘V‘hfik H ' «~ch 5 3 “(QM-Hm cm- ‘ a b (0“ “8 o w; ‘OOC- C - (8) 10. Complex 111 in the respiratory chain accomplishes the net transfer of 2 electrons from reduced coenzyme Q (QHZ) to two molecules of cytochrome-c. In concert with this electron transfer, there are protons “pumped” through the inner mitochondrial membrane. A) How is coenzyme Q suited (in terms of redox properties) for its role in receiving electrons from NADH and transferring them (through Complex 111) to cytochrome:c? it tan +YW5RV am. 3' at a 'i'o curb-c .‘L’ MM TICOVQ Z e' d“ 4 4N4. (MAM-:0») B) In what direction are the protons pumped as a consequence of electron transport through Complex III? F, m ' 3‘45 ."(1 'w .‘l-o (mash-3:) out 4mm mm “mm meM L a, ’bmw’un, ,‘ntw-wembfivvq C) What is the current best estimate for the number of protons pumped by Complex 111 per NADH oxidized by Complex 1? F0 “ Y . BCH227 Name if 12 w Number (12) 11. In the F1 complex of mitochondrial ATP synthase, an uhusual property of each enzyme active site is that it binds to the product of the reaction (ATP) tightly enough that the product, in the active site, has about the same stability as the reactants (ADP + Pi). Because of this feature, energy is required to cause ATP to be released from an active site. The proton gradient across the inner mitochondrial membrane is the immediate source of energy that causes ATP to be released from an active site. Proton gradient energy is made available to the F1 complex by the passage of protons through the “c-ring” of the F0 complex. A) How many active sites are there per F1 complex? e ‘ (:2 M?) B) What are the two main components, in terms of potential energy, of the “proton ’ motive force” available from the proton gradient? It I' 6 m, e lecho' abm Mg 7" ' +r dz +4 “1; a 19¢; L elec it foiu— ‘ “+47- 4 lung: 5 t . M f (w (Mar; inhsi-r- bud-NA achs WWI "Mg Ca ,0ij fins 2.. chomqu fol-MAMA Dana‘s? ) Arm auH. («W'M ' 09 5,0111%} «(v-ass inuw-MML. C) Briefly, describe how the F0 complex of ATP synthase transduces energy in the proton gradient into mechanical force. I P7?) Prams $10.4 "fiWsm\ TO. TU) teSuH’S in fobkmwoz' FORWW) i .).\M.\M\,3 9‘s" X (Shkw’fluCM-x "V'gifll-I F1... T‘LM‘S Ynchu/l} “cu-(1.9.4. .240!“ «L'h‘v? 5'2": ‘H’WH 59?)““4‘1 "’1 (7.0?) cmfirrM'M sides. W- ke’df ‘ mfléluflésis 1 I‘d”: ‘ C 6mg; "any:ng custard; “1: 59-57:? A‘mm’L" ‘ (i m D) Scientists found that in normal mitochondria, there are nine c-subunits per c-ring in the F0 complex. Interestingly, they also found that in mutant, UNC mitochondria, there are 15 c-subunits per c-ring. Are the mutant mitochondria more or less efficient in converting proton gradient energy into ATP? (How many protons are required per ATP in each case? [Assume ATP is inside the mitochondria.]) Le 5; (f and _ (1 FT) EL+m = EATP 4am : 113: : rot/MP NHWQ‘ qf'9t/hm‘ W 3MP 3? .21“; .-. = 5’ mi A) . I 5 emf/iurw 3N“, 3””? P / “NC: BCH227 Name Number (8) 12. Protein phosphorylation plays a key role in regulating enzy ' activities. Indicate the effects of phosphorylation on the following enzymes by marking “up” for activation or “down” for inactivation. Glycogen phosphorylase /f‘ ( W Glycogen phosphorylase kinase Triacyl glycerol lipase A IT\ PPl when GM (Glycogen targeting protein) is phosphorylated by insulin—induced kinase PPl when GM (Glycogen targeting protein) is phosphorylated by CAMP-dependent kinase \L/ Glycogen synthase \g/ Glycogen synthase kinase Acetyl CoA carboxylase (4) 13. Write down the chemical structures of covalent intermediates involved in the reactions by branching enzyme and phosphoglucomutase. You do not need to write down a complete chemical structure. But you need to have the structure for the side chain of the active site amino acid and the ‘ nature of the covalent bond in the intermediate. BCH227 Name W Number \ 14. Following are the reactions in a metabolic pathway, arranged NOT in the right order. 0 “a j? R g” {: A 1 i ’” --------- "> * AK ‘0 Rxcxewif€ksflcm sac,» usage \Sx H2 at; “2 ré 312:} NE? ‘1‘ E a » R. a; C (29% 2. R\cf{c WiT/CXS/Coa ---------- --> xcx esp/r xfi/ Hg «3‘ .3 H2 *‘x :t é‘i Kl 0 k {3 3 a :5 1c]: c A ii a .m o _________ __ " xc/ xsx > ENC/{fiQ/CxS/C‘m $42 8 H2 ‘1» a 34»: 0 4 l i? l ---- n e R\C/€\C/C\S/CGR \C/ \S/«r “2 a“; “2 + l 7 C09; ch/c\s/ o O + """""" “> xx“ R a o. e; r: 5 H2 M2 H; I“? (2) A. Name the metabolic pathway which includes these reactions. (l * 0% l M : W» (/6 Ou £5 (£4 (5) B. Arrange the reactions in the right order (use the numerals in front of the reactions). s’ll/B/gx/(IL BCH227 Name K %g/ Number (10) C. From the following lists, identify the enzyme and cofactor involved in each of the reactions given in the previous page. You only need to name the cofactor that is required as a reactant (placed at the left side, or in front of the reaction arrow). Notice that some of the names on the list may be extraneous. If no cofactors are involved, just write down “None”. List of Enzymes: oxygenase, dehydrogenase, thiolase, reductase, hydratase, thioesterase, synthetase, dehydratase List of Cofactors: NADH, NAD+, NADPH, NADP+, ATP, cAMP, FAD, FADHZ, Biotin, Pyridoxal, Vitamin B12 Reaction Enz me Cofactor 1 dehyolvojwd/SQ FM) .4. 2 delayclvojmayga NAP 3 flamingo... liar/paw 4 flilolc’iSQi Mal/LL»! 5 fiwt’fix/HSQ, ...
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2005exam2key - BCH227 Name &amp;quot; Number b A, i i...

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