BCHS 3305                Exam #3                           11/17/08

Multiple-Choice.  Each correct answer gets two points.  Each wrong (or no) answer gets zero point without any extra penalty.

 

o [(a) NAD+; (b) NADH; (c) NADP+; (d) NADPH; (e) FAD]  Choose one from this list to fill in each of the following blanks.

·      As a part of the acetyl-CoA transport across the inner mitochondrial membrane, the conversion of malate to pyruvate by malic enzyme in cytosol requires (#1) ____ as a reactant. 

·      In β-oxidation of fatty acids, the conversion of fatty acyl-CoA to enoyl-CoA by acyl-CoA dehydrogenase requires (#2) ____ as a reactant.

·      In β-oxidation of fatty acids, the conversion of 3-hydroxyacyl-CoA to β-ketoacyl-CoA by 3-hydroxyacyl-CoA dehydrogenase requires (#3) ____ as a reactant.

·      In fatty acid biosynthesis, the conversion of acetoacetyl-ACP to 3-hydroxybutyryl-ACP by β-ketoacyl-ACP reductase requires (#4) ____ as a reactant.

·      For fatty acid biosynthesis in cytosol, the formation of butyryl-ACP from butenoyl-ACP by enoyl-ACP reductase requires (#5) ____ as a reactant. 

·      For further elongation of palmitate in mitochondria, the conversion of enoyl-CoA to acyl-CoA by enoyl-CoA reductase requires (#6) ____ as a reactant. 

·      In the conversion of a saturated acyl-CoA to an unsaturated enoyl-CoA containing a cis double bond, the enzyme desaturase requires (#7) ____ as a reactant.

·      For cholesterol biosynthesis, the formation of mevalonate from hydroxy-methylglutaryl-CoA by hydroxy-methylglutaryl-CoA reductase requires (#8) ____ as a reactant.

o For the activation of fatty acid to acyl-CoA by acyl-CoA synthetase, (#9) ____ are produced as by products.

[(a) ADP + Pi; (b) AMP + PPi]. 

o The inner mitochondrial membrane [(a) contains; (b) does not contain]:

·      (#10) ____ specific carrier proteins which can bind and mediate the DIRECT transport of pyruvate.

·      (#11) ____ specific carrier proteins which can bind and mediate the DIRECT transport of oxaloacetate.

·      (#12) ____ specific carrier proteins which can bind and mediate the DIRECT transport of fatty acyl-CoA.

o For fatty acid β-oxidation, the 3-hydroxyacyl-CoA formed by enoyl-CoA hydratase is in the (#13) ____ [(a) L; (b) D] configuration.

o Propionyl-CoA is converted to the (#14) ____ [(a) S; (b) R] form of methylmalonyl-CoA by propionyl-CoA carboxylase.

o

A desaturase (#15) ____ [(a) can; (b) cannot] introduce a new double bond to the acyl-CoA with the following structure (regardless where the new double bond may be in the molecule).

o The metabolite

can be converted to (#16) ____ by the mammalian 2,4-dienoyl-CoA reductase, and by the bacterial 2,4-dienoyl-CoA reductase to (#17) ____.

 

(a)        (b)

 

(c)                                                                       (d) none of the above

     

o  

o Citrate is an allosteric activator for (#18) ____ [(a) acyl-CoA synthetase; (b) acetyl-CoA carboxylase; (c) β-hydroxy-β-methylglutaryl-CoA reductase].

o In cholesterol biosynthesis, the step-wise conversion of one molecule of mevalonate to one molecule of isopentenyl pyrophosphate consumes a total of (#19) ____ molecule(s) of ATP as reactant.  [(a) 0;  (b) 1;  (c) 2;  (d) 3;  (e) 4]

o The addition of geranyl pyrophosphate to isopentenyl pyrophosphate to form farnesyl pyrophosphate is a(#20)  ____ [(a) head to tail; (b) head to head] reaction.

o HCO3– is required for the synthesis of fatty acid.  In such a process, the carbon from HCO3– (#21) ____ [(a) is; (b) is not] incorporated into the fatty acid product.

o The enzyme squalene epoxidase requires (#22) ____ as substrate(s).

[(a) NADPH but not O2; (b) O2 but not NADPH; (c) neither O2 nor NADPH; (d) both O2 and NADPH]

Phosphatidic acid (#23) ____ a precursor for the synthesis of phosphatidylcholine, and (#24) ____ a precursor for the synthesis of phosphatidylinositol.            [(a) is; (b) is not]

o  (#25) ____ is/are required as substrate(s) for the synthesis of phosphatidylethanolamine from ethanolamine.

[(a) ATP but not CTP; (b) CTP but not ATP; (c) neither ATP nor CTP; (d) both ATP and CTP]

o (#26) ____ is excreted by ureotelic animals as the major end product derived from the amino group of amino acids. [(a) Urea; (b) Uric acid; (c) NH4+]

o The cofactor pyridoxamine phosphate is bound by aminotransferase through a (#27) _____ linkage.  [(a) covalent;  (b) non-covalent]

o The hydrolysis of the ketimine intermediate of aminotransferase by water will produce (#28) _____.  [(a) an amino acid and pyridoxal phosphate cofactor; (b) an amino acid and pyridoxamine phosphate cofactor; (c) a ketoacid and pyridoxal phosphate cofactor;  (d) a ketoacid and pyridoxamine phosphate cofactor.]

o In most organisms, (#29) ____ [(a) only glutamatecan can be oxidatively deaminated by a specific glutamate dehydrogenase; (b) each of the 20 common amino acids can be oxidatively deaminated by their corresponding dehydrogenases].

o Glutamate dehydrogenase is an allosteric enzyme, which can be activated by (#30) ____ [(a) ADP but not GDP;  (b) GDP but not ADP;  (c) ADP and GDP;  (d) none of the above.]

o Several enzymes play a minor role in the deamination of certain amino acids.  For example, a/an (#31) ____ type of enzyme can convert histidine to urocanate and NH4+. 

[(a) oxidase; (b) dehydratase; (c) lyase]

o N-Acetylglutamate is an allosteric activator for the enzyme (#32) ____. [(a) cytosolic Carbomoyl Phosphate Synthetase (CPS) I;  (b) mitochondrial CPS I; (c) cytosolic CPS II; (d) mitochondrial CPS II]

o In the urea cycle, all carbon atoms from the carbon skeleton of aspartate are recovered in (#33) ____. [(a) urea; (b) arginine; (c) fumarate]

o For the synthesis of one urea molecule from HCO3- and NH3, a total of (#34) ____ATP molecule(s) is/are required as substrate(s).  [(a) 0;  (b) 1;  (c) 2;  (d) 3;  (e) 4]

o The catabolism of the carbon skeletons of certain amino acids leads to the formation of pyruvate.  Pyruvate feeds into gluconeogenesis by being converted directly to a glucogenic metabolite (#35) ____. [(a) α-ketoglutarate; (b) succinyl-CoA; (c) fumarate; (d) oxaloacetate].

o Following is a list of catabolites derived from amino acids.

Acetyl-CoA; Acetoacetate; Pyruvate; α-Ketoglutarate; Oxaloacetate; Fumarate; Succinyl-CoA

 

An amino acid is ketogenic if its degradation leads to the formation of acetyl-CoA or acetoacetate as the earliest catabolite from the above list.  On the other hand, an amino acid is glucogenic if its degradation leads to the formation of any one of the other five catabolites as the earliest degradative product from the above list.

Choose from [(a) Valine; (b) Threonine; (c) Serine; (d) Tryptophan; (e) Glutamate] to answer the followings:

·      (#36) _____ is both glucogenic and ketogenic because it produces pyruvate by one pathway and acetoacetate by another pathway as the earliest catabolic products.

·      (#37) _____ is glucogenic only because its degradation produces α-ketoglutarate as the earliest catabolic product.

·      (#38) _____ is glucogenic only because its degradation produces pyruvate as the earliest catabolic product.

·      (#39) _____ is glucogenic only because its degradation produces succinyl-CoA as the earliest catabolic product.

·      (#40) _____ is both gucogenic and ketogenic because it produces pyruvate by one pathway and acetyl-CoA by another pathway as the earliest catabolic products.

o Hydroxymethylglutaryl-CoA syhthase is involved in the synthesis of (#41) ____.  [(a) ketone bodies but not cholesterol;  (b) cholesterol but not ketone bodies;  (c) both ketone bodies and cholesterol;  (d) neither ketone bodies nor cholesterol]

o β-Hydroxybutyrate dehydrogenase catalyzes the conversion of acetoacetate to the ketone body β-hydroxybutyrate in the (#42) ____ [(a) L-; (b) D-] configuration.

o The hydroxymethylglutaryl-CoA (#43) ____ [(a) lyase; (b) reductase] is involved in the formation of the ketone body acetoacetate.

o For the utilization of ketone bodies, the conversion of β-hydroxybutyrate to acetoacetate by β-hydroxybutyrate dehydrogenase requires (#44) ____ as a reactant.  [(a) NAD+;  (b) NADH;  (c) NADP+;  (d) NADPH]

o For human, methionine is (#45) ____ and proline is (#46) ____ amino acid.  [(a) an essential; (b) a nonessential]

o The conversion of homocysteine to methionine requires (#47) ____ as a one-carbon donor. [(a) N5-methyl-THF; (b) N5,N10-methylene-THF; (c) N5,N10-methenyl-THF; (d) N5-formyl-THF; (e) N10-formyl-THF] (where THF = tetrahydrofolate)

o The conversion of N5-formyl-THF to N5,N10-methenyl-THF is (#48) ____ reaction.  The conversion of N5,N10-methylene-THF to N5-methyl-THF is (#49) ____ reaction. 

[(a) an oxidation; (b) a reduction; (c) neither an oxidation nor a reductation]

o For the following tetrahydrofolates, the oxidation state of (#50) ____ is equivalent to that of formate. [(a) N5-methyl-tetrahydrofolate; (b) N5,N10-methenyl-tetrahydrofolate; (c) N5,N10-methylene-tetrahydrofolate]