Answers to the questions are marked on your test answer sheet.

BCHS 3305 Exam #1 09/21/09

Multiple-Choice. Fill in the circle under the “letter” for your answer to each question. Each correct answer gets two points. A wrong answer or no answer gets zero point but no extra penalty.

On your answer sheet, identify (a) your name AND (b) the last four digits of your UH student ID number (It is NOT your SS#).

Ø Glycogen phosphorylase catalyzes the formation of (#1) ____ as a product whereas the glycogen debranching enzyme can generate (#2) ____ as a product. [(a) glucose; (b) glucose-1-phosphate; (c) glucose-6-phosphate] (97-#11)

Ø In glycogen metabolism (including degradation and synthesis), the enzyme (#3) ____ can utilize inorganic phosphate (Pi) as a substrate in its catalytic reaction. [(a) glycogen phosphorylase; (b) glycogen debranching enzyme; (c) UDP-glucose pyrophosphorylase; (d) glycogen synthase; (e) branching enzyme]

Ø Two branches of a glycogen molecule are shown below as A and B with each circle (open or filled) as a glucose unit. The only α(1-6) bond is shown. As such,

· glycogen phosphorylase can utilize (#4) ____ [(a) both A and B as substrates, (b) A or B as a substrate but not both, (c) neither A nor B as a substrate].

· the debranching enzyme can utilize (#5) ____ [(a) only A as a donor and B as an acceptor; (b) only B as a donor and A as an acceptor; (c) either A or B as a donor and the other chain as an acceptor; (d) neither A nor B as a donor] in transferring a segment of glucose units from one branch to another.

Ø The enzyme UDP-glucose pyrophosphorylase by itself can (#6) ____ [(a) catalyze only the conversion of Glucose-1-P + UTP ® UDP-glucose + PPi in the direction as shown by the arrow but not in the reversed direction; (b) catalyze only the conversion of UDP-glucose + PPi ® Glucose-1-P + UTP in the direction as shown by the arrow but not in the reversed direction; (c) catalyze the reversible conversion of Glucose-1-P + UTP D UDP-glucose + PPi].

Ø In a glycogen molecule, branches A and B containing a single α(1-6) bond are shown below. The “branching enzyme” (#7) ____ cut off a segment of glucose units from the end of branch A for transferring to another branch, and the glycogen branching enzyme (#8) ____ utilize branch B as an acceptor of a new segment of glucose units (not necessarily from the same glycogen) to generate a new branch point. [(a) can; (b) cannot]

Ø Allosteric activation or inhibition is an important mechanism for metabolic regulation. Following such a mechanism, glucose is an allosteric inhibitor for (#9) ____ [(a) glycogen phosphorylase a; (b) glycogen phosphorylase b; (c) glycogen synthase], and fructose-2,6-bisphosphate is an allosteric activator for (#10) ____ [(a) phosphofructokinase; (b) fructose-1,6-bisphosphatase; (c) phosphofructokinase-2; (d) fructose-2,6-bisphosphatase-2].

Ø In glycogen metabolism and under normal physiological conditions, (#11) ____ [(a) the more active R form; (b) the less active T form] is the predominant species of glycogen phosphorylase b. Moreover, only the (#12) ____ [(a) R form; (b) T form] of glycogen phosphorylase b can be phosphorylated by ATP.

Ø In glycogen metabolism, higher activity of protein kinase A will step-wise lead to (#13) ____ [(a) higher; (b) lower] activity of glycogen phosphorylase.

Ø Isoleucine(#14) ____ [(a) is; (b) is not] an active precursor for gluconeogenesis in animals.

Ø For gluconeogenesis, the conversion of pyruvate to phosphoenol pyruvate is a rather energy-consuming process in which pyruvate carboxylase requires (#15) ____ and phosphoenol pyruvate carboxykinase requires (#16) ____ as a substrate. [(a) ATP; (b) GTP; (c) UTP].

Ø For the indirect transport of one molecule of oxaloacetate from mitochondrial inner space to cytosol through the malate dehydrogenase-coupled pathway, one molecule of NADH is (#17) ____ [(a) generated; (b) consumed] inside a mitochondrion.

Ø For the synthesis of 1 molecule of glucose from 2 molecules of pyruvate in gluconeogenesis, (#18) ____ [(a) 1; (b) 2; (c) 3; (d) 4] molecule(s) of ATP will be utilized as substrate.

Ø A decrease in blood glucose level will step-wise lead to (#19) ____ [(a) an increase; (b) a decrease] in the activity of phosphofructokinase.

Ø For those reactions of the glyoxylate pathway that occur WITHIN the glyoxysome, FAD (#20) ____ [(a) is; (b) is not] required.

Ø For those reactions of the glyoxylate pathway that occur WITHIN the mitochondrion, FAD (#21) ____ [(a) is; (b) is not] required.

Ø Usually NADH and NADPH have different metabolic functional roles. (#22) ____ is primarily involved in ATP synthesis by oxidative phosphorylation whereas (#23) ____ is important in reductive biosynthesis. [(a) NADH; (b) NADPH]

Ø In the pentose phosphate pathway:

· The reaction catalyzed by phosphogluconate dehydrogenase involves (#24) ____ [(a) an oxidation; (b) a reduction; (c) neither an oxidation nor a reduction] of 6-phosphogluconate to generate ribulose-5-phosphate.

· Xylulose-5-phosphate is generated from ribulose-5-phosphate by an enzyme of the type of (#25) ____ [(a) lactonase; (b) isomerase; (c) epimerase (d) transketolase; (e) transaldolase].

· Sedoheptulose-7-phosphate is a product of the reaction catalyzed by an enzyme of the type of (#26) ____ [(a) lactonase; (b) isomerase; (c) epimerase (d) transketolase; (e) transaldolase].

Ø A triacylglycerol containing three linoleic acid molecules through ester linkages is expected to have (#27) ____ [(a) a higher melting point than; (b) the same melting point as; (c) a lower melting point than] another type of triacylglycerol containing three oleic acid molecules.

Ø For naturally occurring fatty acids that contain double bonds in their aliphatic chains, the double bonds are almost always (#28) ____ [(a) cis; (b) trans] in configuration.

Ø In phosphatidylethanolamine, the phosphoethanolamine group is esterified to -CH₂-OH at the (#29) ____ [(a) pro-S position 1; (b) pro-S position 3; (c) pro-R position 1; (d) pro-R position 3] of the glycerol molecule.

Ø A cerebroside is a (#30) ____ [(a) sphigophospholipid; (b) sphingoglycolipid].

Ø (#31) ____ [(a) Sphingophospholipid; (b) Sphingoglycolipid] is a major component of the membranous structure that surrounds and electrically insulates nerve cells.

Ø In general, single-hydrocarbon-tail lipids tend to have (#32) ____ [(a) a higher; (b) the same; (c) a lower] critical micelle concentration than double-hydrocarbon-tail lipids (assuming all hydrocarbon tails are fully saturated and similar in length).

Ø The outer surface of a lipid micelle is a lipid (#33) ____ [(a) monolayer; (b) bilayer].

Ø (#34) ____ [(a) All; (b) Some; (c) None] of the extrinsic proteins are trans-membrane proteins (i.e. they span the entire thickness of a membrane).

Ø In general, (#35) ____ [(a) peripheral but not integral; (b) integral but not peripheral; (c) neither peripheral nor integral; (d) both peripheral and integral] proteins are asymmetrically associated with biological membranes.

Ø (#36) ____ [(a) All; (b) Some; (c) None] of the “nonmediated” transport systems can generate a net flow of molecules from a low concentration compartment through a membrane barrier to a high concentration compartment.

Ø (#37) ____ [(a) All; (b) Some; (c) None] of the “mediated” transport systems can generate a net flow of molecules from a low concentration compartment through a membrane barrier to a high concentration compartment.

Ø A uniport system (#38) ____ [(a) must always be; (b) may or may not be; (c) can never be] an electroneutral transport system.

Ø A neutral compound X can pass, by free diffusion, through a membrane barrier which separates two compartments. If the net flow of the compound X is from the “out” compartment that is high in X concentration to the adjacent “in” compartment that is low in X concentration, such a process is associated with a D(defined as - ) that is (#39) ____ [(a) positive; (b) negative; (c) zero; (d) any of the above] in value.

Ø The free diffusion of a neutral molecule through a membrane (#40) ____ [(a) should; (b) should not] be affected by any existing membrane potential of the system.

Ø An ionophore molecule (#41) ____ [(a) will always; (b) may or may not; (c) will never] move from one side to the other side of a membrane.

Ø The efficiency of gramicidine as an ionophore (#42) ____ [(a) should; (b) should not] be highly sensitive to temperature.

Ø A carrier protein (#43) ____ [(a) is always; (b) may or may not be; (c) is never] involved in a passive transport system.

Ø For the plasma membrane (Na⁺-K⁺)-ATPase, the phosphorylated form of the enzyme has a (#44) ____ [(a) high; (b) low] affinity for Na⁺ binding.

Ø For the Ca²⁺-ATPase, the enzyme can be phosphorylated by ATP when it is (#45) ____ [(a) free from any Ca²⁺ binding; (b) bound by one Ca²⁺; (c) bound by 2 Ca²⁺].

Ø The normal operation of active glucose transport from outside of the brush border cells of intestinal villi all the way to blood capillaries on the other side of the brush border cells require (#46) ____ [(a) only a symport system; (b) only an antiport system; (c) only a uniport system; (d) two of the three systems listed above; (e) all three systems listed above.]

Ø Bacterial lactose permease is a H⁺-lactose (#47) ____ [(a) electroneutral antiport; (b) electrogenic antiport; (c) electroneutral symport; (d) electrogenic symport].

Ø The molecule as shown is (#48) _____.

[(a) ribose-5-P; (b) ribulose-5-P; (c) xylulose-5-P]

Ø The molecule as shown is (#49) _____.

[(a) oleic acid; (b) linoleic acid; (c) α–linolenic acid; (d) none of the above ]

Ø The molecule as shown is (#50) a _____.

[(a) ceramide; (b) cerebroside; (c) ganglioside; (d) sphingomyelin; (e) none of the above]