MCAT FSQ Bio/Biochem

Which portion of the central nervous system confers balance by coordinating the activity of various motor units? Question 13 Answer Choices A. Cerebrum B. Cerebellum C. Medulla D. Hippocampus

B

Decreased secretion of aldosterone has all of the following effects EXCEPT: Question 30 Answer Choices A. increased loss of Na + in urine. B. decrease in extracellular fluid volume. C. increase in arterial pressure. D. increase in urine volume.

C

(+)-Ginkgolide B is a diterpenoid trilactone with six five-membered rings, and is extracted from the root bark and leaves of the Ginkgo biloba tree. This molecule has blood-brain barrier permeability, the molecular formula C20H24O10 and a molecular weight of 424.4 g/mol. This molecule must contain: Question 57 Answer Choices A. four isoprene units, additional functional groups and is able to perform simple diffusion through endothelial cells connected by tight junctions. B. four isoprene units, no additional functional groups and is able to perform simple diffusion through endothelial cells connected by tight junctions. C. four terpene units, additional functional groups and is able to perform simple diffusion through neurons connected by tight junctions. D. four isoprene units, additional functional groups and is able to perform simple diffusion through endothelial cells connected by gap junctions.

A

A barometer is made by erecting an evacuated glass tube over a dish filled with mercury. Atmospheric pressure at sea level causes the mercury to rise inside the tube. If this barometer were moved from sea level to a mountain several kilometers in altitude, the mercury column would most likely: Question 14 Answer Choices A. fall due to the decreased atmospheric pressure. B. rise due to the decreased atmospheric pressure. C. fall due to the increased atmospheric pressure. D. rise due to the increased atmospheric pressure.

A

TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) is a method for detecting DNA fragmentation by labeling the terminal end of nucleic acids. BrdU (5-bromo-2'-deoxyuridine) can also be used in staining protocols, as this synthetic nucleoside can be incorporated into nucleic acids during replication instead of thymidine. Tumor cells have: Question 58 Answer Choices A. minimal TUNEL staining due to their low apoptotic rate, but strong BrdU staining due to active genome replication. B. strong TUNEL staining due to their high apoptotic rate, and strong BrdU staining due to active genome replication. C. strong TUNEL staining due to their high apoptotic rate, but weak BrdU staining due to minimal genome replication. D. minimal TUNEL staining due to their low apoptotic rate, and weak BrdU staining due to minimal genome replication.

A

The amphoteric character of amino acids best explains their ability to: Question 47 Answer Choices A. form dipolar ions. r B. form peptide bonds. C. contribute directly to a protein's secondary structure. D. dissolve in nonpolar solvents.

A

Which of the following describes the molecular geometry of a carbon dioxide molecule? Question 24 Answer Choices A. Linear B. Trigonal planar C. Tetrahedral D. Bent

A

E. coli is a generally harmless bacterium, often used for research purposes. Some strains of E. coli live mutualistically inside human digestive tracts. Sometimes these bacteria can cause infection outside the iinfection outside the intestinal tract, most notably in the urinary tract, the biliary tract, and the nervous system. In which of the following structures is E. coli most likely to cause infection? Question 28 Answer Choices A. Trachea B. Bladder C. Small intestine D. Large intestine

B

Muscle fibers are composed of small contractile units called sarcomeres. During contraction, which of the following occurs within a sarcomere? Myosin filaments shorten. Actin filaments shorten. Overlap between actin and myosin filaments increases. Question 46 Answer Choices A. I only B. III only C. II and III only D. I, II, and III

B

Which of the following equilibria could be present in a buffered solution? Question 44 Answer Choices A. HCl( aq ) H + ( aq ) + Cl - ( aq ) B. H 2 CO 3 ( aq ) H + ( aq ) + HCO 3 - ( aq ) C. H2O 2 ( aq ) + 2KI( aq ) 2KOH( aq ) + I 2 ( aq ) D. CaCl 2 ( aq ) Ca 2+ ( aq ) + 2 Cl - ( aq )

B

Which of the following is the LEAST characteristic of the Krebs cycle? Question 59 Answer Choices A. Oxaloacetate is combined with acetyl-coA to produce citrate. B. Most of the energy is produced through substrate-level phosphorylation. C. Most of the energy is produced indirectly through high-energy electron carriers. D. 6 NADH, 2 FADH2, and 2 GTP are produced per glucose.

B

A semipermeable membrane separates an aqueous solution of 0.003 MNaCl from an aqueous solution of 0.0025 MBaF2. With this apparatus, one would observe that water crosses the membrane: Question 31 Answer Choices A. from the BaF 2 solution to dilute the NaCl solution. B. from the NaCl solution to dilute the BaF 2 solution. C. from the BaF 2 solution to concentrate the NaCl solution. D. from the NaCl solution to concentrate the BaF 2 solution.

B

A tall plant with curly leaves (TT/CC ) was crossed with a dwarf plant with straight leaves (tt/cc). Two of the resulting F1s were crossed with each other and produced F2s as follows: 34 tall plants with curly leaves 4 dwarf plants with straight leaves 11 tall plants with straight leaves 12 dwarf plants with curly leaves. Based on these results, are the genes for plant height and leaf shape linked? Question 22 Answer Choices A. No, since recombination occurred. B. No, since the phenotype ratio is close to the expected ratio for this cross. C. Yes, since the recombination frequency is less than 50%. D. Yes, since there are considerably fewer recombinant plants than expected.

B

All of the following statements regarding enzymes are true EXCEPT that they: Question 13 Answer Choices A. can be stereospecific in substrate recognition. B. alter reaction equilibria. C. are often regulated by feedback inhibition. D. reduce the activation energy of reactions.

B

During spermatogenesis, spermatids: Question 23 Answer Choices A. are frozen in meiosis II until after fertilization. B. have already undergone meiotic recombination. C. have four copies of the genome per cell. D. have no nucleus.

B

Fluoroquinolones are a new class of antibiotics that are extremely effective against a wide range of bacteria. It has been determined that fluoroquinolones enter cells along with water via a passive transport mechanism. After exposing both bacterial and human cells to high concentrations of fluoroquinolones, a researcher discovered that, in the bacterial cells only, the DNA was nicked and supercoiling had been disrupted. Of the following, the most likely explanation for this is that fluoroquinolones: Question 21 Answer Choices A. are unable to diffuse into human cells. B. interfere with DNA polymerase, which is not present in human cells. C. interfere with DNA gyrase, which is not present in human cells. D. interfere with DNA helicase, which is not present in human cells.

C

Tryptophan, an essential amino acid found in banana, turkey, and milk proteins, can induce sleep in some people. Warm milk causes greater sleepiness than cold milk because heating the milk: Question 39 Answer Choices A. reduces the solubility of tryptophan in the milk. B. causes hydrolysis of lactose, releasing tryptophan. C. releases free tryptophan from proteins, causing more rapid intestinal absorption. D. increases the rate of absorption of tryptophan by the stomach.

C

Which of the following are products of the pentose phosphate pathway? NADH NADPH Ribose-5-phosphate Question 53 Answer Choices A. I only B. III only C. II and III only D. I, II, and III

C

Which of the following best describes the role of fructose-2,6-bisphosphate? Question 36 Answer Choices A. It exerts reciprocal control on glycolysis and gluconeogenesis by stimulating fructose-1,6-bisphosphatase and inhibiting phosphofructokinase. B. It exerts reciprocal control on glycolysis and gluconeogenesis by stimulating phosphofructokinase and inhibiting hexokinase. C. It exerts reciprocal control on glycolysis and gluconeogenesis by stimulating phosphofructokinase and inhibiting fructose-1,6-bisphosphatase. D. It exerts reciprocal control on glycolysis and gluconeogenesis by stimulating hexokinase and inhibiting fructose-1,6-bisphosphatase.

C

All of the following contribute to speciation EXCEPT: Question 12 Answer Choices A. geographic isolation of populations. B. genetic diversity. C. natural selection. D. maintenance of Hardy-Weinberg equilibrium.

D

During the exponential phase of bacterial growth, bacteria are reproducing by: Question 11 Answer Choices A. sexual reproduction. B. transduction. C. conjugation. D. binary fission.

D

Most biological unsaturated fatty acids are cis and contain non-conjugated double bonds. Because of this, additional steps are required in β-oxidation. These most likely include: Question 45 Answer Choices A. Changing a single double bond to trans via a reductase enzyme in the mitochondrial matrix. B. Combining two double bonds via a reductase enzyme (which uses NAD+ as a reducing agent), then changing the resultant trans double bond to cis via an isomerase enzyme. C. Moving a single double bond down the fatty acid chain via a translocase enzyme in the mitochondrial matrix. D. Combining two double bonds via a reductase enzyme (which uses NADPH as a reducing agent), then changing the resultant cis double bond to trans via an isomerase enzyme.

D

Some vitamins are essential to humans because they act as precursors of: Question 54 Answer Choices A. auxins. B. glucose. C. enzymes. D. coenzymes.

D

The diaphragm plays an important role in respiration. During inspiration, the diaphragm: Question 38 Answer Choices A. relaxes, causing alveolar pressure to drop below atmospheric pressure. B. contracts, causing alveolar pressure to rise above atmospheric pressure. C. relaxes, causing alveolar pressure to rise above atmospheric pressure. D. contracts, causing alveolar pressure to drop below atmospheric pressure.

D

Which of the following intermolecular attractions will exhibit the greatest strength? Question 52 Answer Choices A. London dispersion forces B. Induced dipole interactions C. Instantaneous dipole interactions D. Hydrogen bonds

D