B/B AAMC Sample Test - longer version
Terms in this set (66)
GTP, ATP, CTP, TTP are most closely related to
GAP belongs to what class of enzymes
move a functional group from one molecule to another
catalyze the interconversion of isomers, including both constitutional and stereoisomers
--Protein transcription occurs in the ER
--Proteins are then transported to Golgi apparatus for post translational modification, processing and packaging for proper localization
--would reverse the motion and return the protein to ER
#6. Which of the following experiments would provide the best supporting evidence that neutrophils are the cause of the reperfusion injury?
Performing the ischemia/reperfusion experiment using neutrophil-depleted animals ans examining whether the degree of tissue damage is reduced
--Coz this experiment focuses on the effects of presence and absence of neutrophils as a whole and that's what the question is asking
#8. Scientists claimed that antibody B offers a better means for preventing organ injury than agents such as free radical or protease inhibitors. Which of the following reasons offers the best support for this claim?
Antibody B can block the initiation of events that result in the release of harmful, biologically active molecules
--Because the results of the experiment presented in the passage show that the presence of antibody B, which is directed at subunit B, significantly reduces tissue injury. The results also suggest that the function of antibody B is to adhere the neutrophil to vascular endothelium, which occurs before the release of toxic molecules by the neutrophil. Thus, the use of antibody B would be proactive treatment that prevents the neutrophil adherence and the subsequent release of free radicals and proteases, rather than reactive treatment , such as free radical and protease inhibitors. This supports the clain that antibody B is a better treatment
#9. Scientist wanted to use antibody B clinically (to treat humans), but this proposal was rejected. Which of the following is the most logial reason for the rejection?
Because the antibody was generated in the mouse, repeated usage in the same patient would elicit the production of human anti-mouse antibodies
--Human immune system will recognize the mouse antibody as a foreign substance (antigen) and generate an immune response towards it, which may include a mild to severe allergic reaction. The immune response will generate antibodies against the mouse antibody, limiting its usefulness as a treatment
#10. A neutrophil has point mutations in the genes coding for the alpha and beta subunits of the adhesion receptor. However, this cell can still migrate through endothelium. Which of the following conclusions about the effect of this mutation can be drawn?
The cell can bind to endothelium
--THINK THAT THE MUTATION ISNT CHANGING ANYTHING IN THE CELL SO ITS GONNA KEEP DOING THE SAME FUNCTION IT DID BEFORE!!!
-- According to the passage, neutrophil migration into the endothelium occurs after the adhesion to endothelium. Thus, this cell must still be able to bind to endothelium, suggesting that mutation either does not affect the cell's adherence ability or enhances it
occur when one nucleotide in DNA is swapped for another
subcategorized as silent, missense, or nonsense mutations
Occur when the change in nucleotide has no effect on the final protein synthesized from the gene
occur when the change in nucleotide results in substituting one amino acid for another in the final protein
occur when the change in nucleotide results in substituting a stop codon for an amino acid in the final protein
#11 A hypothesis states that all mutations leading to hemophilia occur within the factor VIII gene. Which of the following pairs of inheritance patterns would fail to support this hypothesis?
I. Normal sons born to hemophiliac fathers
II. Normal sons born to hemophiliac mothers
III. Hemophiliac sons born to hemophiliac fathers
IV. Hemophiliac daughters born to normal fathers
II and IV only
-- passage states that hemophilia is a x-linked disease
--neither II nor IV show X-linked inheritance pattern
--Thus the inheritance patterns would not support the hypothesis that all mutations leading to hemophilia occur withing the Factor VIII gene.
--Pattern II is not consistent with X-linked inheritance, a mother homozygus for a recessive X-linked gene will ALWAYS pass that recessive gene to her son, and thus a normal cannot be produced
--Pattern IV is not consistent with X-linked inheritance because a daughter inherits one X-chromosome from her father; it would NOT be possible for a daughter that inherits one normal X-linked allele to have an X-linked recessive disorder, as this requires two recessive X-linked alleles
#12. A scientist claimed that hemophilia is caused by a functional deficiency in the factor VIII. The evidence in the passage that would best support this claim is that Factor VIII is:
Able to relieve symptoms of hemophilia
--The passage states that the symptoms of hemophilia can be at least partially alleviated by administration of functional Factor VIII, which would help encounter functional deficiencies in Factor VIII in the affected individual.
--All other options can be characteristics of both functional and non functional proteins and, thus, do not provide the best support for the claim
#13. The cutting of introns and the splicing associated with the expression of the Factor VIII gene occur during which of the following steps in the protein-synthesis process?
DNA --> mRNA
--Because removal of introns and splicing of the splicing of the remaining pieces (exons) is a step in the production of mature mRNA from the transcript produced from DNA (pre-mRNA)
#14. Recombinant DNA technology allows scientists to mass produce some human proteins by transferring hum genes into bacteria. The characteristic of bacteria that would most likely prevent Factor VIII from being produced in this was is that bacteria:
Lack of mechanism for splicing out of introns
-- According to the passage, the synthesis of Factor VIII requires mRNA spilcing. mRNA processing does not occur in prokaryotes . Because transcription in prokaryotes occurs in the cytoplasm, ribosomes are able to bind and begin translation even before transcription is complete; prokaryotic mRNA require no additional processing after transcription.
In Oxidative phosphorylation - Cyt C acts as
1- electron carrier
Cytochrome c is a heme protein that only cycles between a ferrous and ferric state during oxidative phosphorylation.
#17. Which primer is most suitable for PCR?
The one that has a HIGH G-C content and have G-C base pairs at 5' and 3' end
#18. In which phase of meiosis does NON DISJUNCTION occur?
FAILURE of homologous chromosomes to separate during anaphase I or meiosis or the failure o sister chromosomes to separate during anaphase II of meiosis II
#20. In the assay presented in figure 2, which combination of Lys529 codon (AAA or AAG) and genetic background (wold-type or deltayqeV) resulted in the highest level of mistranslation of the codon
AAG codon in the deltayqeV background
-- Based on the passage, levels of mistranslation of the Lys529 codon can be determined by measuring relative firefly luciferase activity (the FL to RL activity ratio). Because Lys529 is critical for FL activity, mistranslation of Lys529 will reduce FL activity. Lower FL activity reduces the FL to RL activity ratio (assuming that RL activity is not affected, or as affected, by mistranslation). According to Fig 2, the FL/RL ratio is lowest when Lys529 is encoded by AAG in the deltayqeV background
#21. According to the passage, CDKALI deficiency most likely causes which of the following to increase the mouse B(beta) cells?
MISFOLDING OF PROINSULIN
According to the passage:
-CDKAL1 is used in the synthesis of ms2t6A
-SO deficiency of CDKAL1 prevents the synthesis of ms2t62A, which is needed for ACCURATE translation of lysine codons
- This would cause abberant transcript processing during insulin synthesis, as the transcript contains two lysine codons.
-Mistranslation of codons would most likely INCREASE protein MISFOLDING
#22. Based on the passage, the level of which of the following is most likely lower in nonfasting wild-type mice than in nonfasting Cdkal1-/- mice?
Blood glucose levels
--Because according to fig 3 and 4, wild-type mice produce more proinsulin in response to a glucose injection and process more proinsulin to insulin than do Cdkal1-/- mice. Insulin stimulates cellular uptake of glucose, and higher cellular uptake of glucose would result in lower blood glucose levels
Stimulates cellular uptake of glucose
For Data-based questions
READ THE AXIS!!!!!
#23. Which feature of the kinetics of L-Alanine transport would provide evidence that DOM is an important source of nutrients under low-food conditions?
High affinity transport (Kt) of L-Alanine
-Under low food conditions, the capacity of transport is irrelevant as no transporters are saturated with L-alanine
-However, the transporter's affinity for L-alanine would be important as only HIGH AFFINITY transporters will be able to facilitate L-alanine uptake at low concentrations
#24. If [amino acid] transport protein is increased, the transport affinity Kt of L-alanine will:
Kt value is NOT dependent on [amino acid] transport protein
#26. If D-alanine is used in protein synthesis instead of L-alanine, then protein synthesis will be:
only L-isomers are used to form proteins during ribosomal protein synthesis
Average metabolic rate
will enable an organism to determine how long the stored energy reserves will last
LOWER metabolic rate = longer lasting energy reserves = best suited to withstand periods of long term nutrient deprivation
ATP in aerobic vs anaerobic
#ATP in aerobic = 38
#ATP in anaerobic = 2
#29. The figure below shows a population growth curve for a bacterial colony before and after the addition of a polysaccharide.
Which of the following most likely explains why the bacterial colony did NOT grow immediately after the polysaccharide was added?
The digestive enzymes for the polysaccharides had to be transcribed and translated
GADPH- where is it found?
Found in EUCHROMATIN
- Housekeeping gene
-gene that is always turned on must be accessible to transcription factors
-Euchromatin is in a loose conformation and readily accessible for transcription
#31. Which amino acids- neutral but zwitterionic at pH 7, despite possessing two nitrogen atom in its formula
GLUTAMINE, ASPARAGINE, TRYPTOPHAN
- carry equal amount of positive and negative charge a neutral pH
#32. Switching of var gene expression probably most directly benefits P. falciparum by reducing the parasite's
Elimination by human adaptive system
-specific var gene expressed switches, so does the antigenicity of PfEMP1 expressed on the erythrocyte surface. Thus, it is most , likely that antibodies that bind a specific PfEMP1 variant will not bind the next variant that is expressed, so a new adaptive immune response will have to be mounted against a new variant.
#33. The information in the passage supports the hypothesis that which type of filament is involved in the transport of var genes from heterochromatin to the active var gene expression site?
--Because discusses the role of actin in var gene silencing, and actin filaments are microfilaments
Actin filaments are
#34. The information in the passage suggests that which symptom or characteristic of malaria is PfEMP1-mediated?
Blood vessel blockage
PfEMP1 binds the parasite infected erythrocytes to endothelium and RBCs stuck to blood vessel walls likely cause blood vessel blockage
#35. If a cerebral malaria-causing infected erythrocyte, as described in the passage, lost its adhesion to endothelium, it would most likely first flow into which type of blood vessels
--Coz they are the first type of vessels downstream a venule
-- According to passage, binding of erythrocytes to brain VENULE endothelium causes cerebral malaria
--So if the binding/adhesion is lost, erythrocytes will flow first into VEINS
#36. Fewer visual pigment molecules are available to absorb light- which nervous system response occurs?
Fewer signals of weakly perceived color are sent to the brain
--Visual pigments absorb light
--So if there are fewer pigments, fewer signals of weakly perceived color will be sent to the brain
#38. A mother and father with normal color vision have a son who is color-blind with green pigment absent. What genotype did the mother most likely have?
Both red and green color defects are sex-linked, the mother must carry a defective allele for green color information only
#39. The genes for red-green color blindness will affect production of proteins in which of the following types of cells?
Visual receptor cells in the retina
--Photoreceptors, which are visual receptor cells in the retina , absorb light
#40. Which of the following organelles would be relatively more abundant in BAT (brown adipose tissue) than in white adipose tissue?
-- BAT is a specialized adipose tissue that contains large numbers of mitochondria generate heat during thermogenesis
#42. According to the passage, the pineal gland has what effect on thermogenesis in wintering natural populations of golden hamsters?
No effect, because BAT mass was equivalent in Normal/Sham and Normal/Px hamsters
--This is the ans coz the other choices examine effect of high temp exposure. The question asks the effect of the pineal gland on thermogenesis in wintering natural populations of hamsters. According to the data in table, BAT mass values for the Sham and Px groups, 275mg and 287mg respectively, did not differ significantly, so there was no effect.
#43. Consider an experiment in which normal golden hamsters are injected with either pineal gland extract (Pgex) or with physiological saline (Psal). Which of the following results would NOT validate the results of the first experiment?
Testes weights of Pgex/Hot hamsters are greater than those of Psal/Hot hamsters
--Because based on the data, testes weights in the Pgex/Hot hamsters are expected to be lower than those of Psal/Hot hamsters. From the data in the table, the testes weights of the sham-operated group (0.8 g) were significantly lower than those of the Px group (1.4 g) when both groups were exposed to high temp. In the experiment under consideration, Pgex replicates the presence of pineal secretions and corresponds to the sham-operated group, whereas Psal corresponds to the Px groups
#44. The individual cells making up a tissue differ from single celled organisms such as paramecium in that only the latter:
A. reproduce by mitosis
B. have subcellular organelles
C. are capable of extended independent life
D. can metabolize nutrient molecules
C. are capable of extended independent life
--Because rest three options are true for tissues!!!
#45. When a striated cell metabolizes glucose in the complete absence of O2, which of the following substances is NOT produces in a significant amount?
Coz in the absence of oxygen, pyruvate is converted to lactate in the cytoplasm and is not transported to the mitochondria to be converted to acetyl-coA
#47. A fatty acid is comprised of a long carbon hydrocarbon tail and a head consisting of:
A carboxyl group
Because a fatty acid contains a carboxylic acid head group and a hydrocarbon tail
#49. Would Cl- concentration of the RBCs be expected to be greater in the systemic veins or the systemic arteries
Veins, because HCO3- ions is higher in veins than in arteries
--Systemic veins and systemic arteries carry high and low carbondioxide levels, respectively. The passage states that Cl- ions enter the RBCs to equalize the HCO3- ions that leave the RBCs, and equation 1 shows that HCO3- ions are produced by a reaction involving carbondioxide
#50. O2 dissociates more readily from Hb in an acidic environment. This dissociation will therefore occur most readily when the Pco2 is:
High, because equation 1 will proceed to the right
The analysis of Equation 1 leads to the conclusion that increasing the concentration of CO2 will result in higher levels of H+ (lower pH) based on LeChatelier's principle. The lower pH will increase the dissociation of oxygen
#51. Lung capillaries are so narrow that RBCs must pass through them in single file. This feature aids respiration by:
Giving maximum exposure of each RBC to diffusing gases
#52. By allowing STx to move from early endosome to the Golgi, the subunit B permits the toxin to bypass which organelle?
because by its presence in the early endosome, STx would be bound for the lysosome without the retrograse trafficking
#53. The most likely result of various alanine to proline mutations in subunit A is:
Loss of secondary structure
--Because proline disrupts the alpha helices, and subunit A is primarily alpha-helical , which is a form a secondary structure
#54. Several strains of STx-producing E. coli are responsible for disease. Despite the availability of antibiotics that lyse E. coli cells, the reason this is NOT a recommended course of treatment is because:
Because bacterial lysate will disrupt host translation
--because the reason antibiotics are contraindicated for STx-producing bacterial infections is that increased release of STx will cause increased cleavage of ribosomal proteins and subsequent disruption of translation. Cell lysis will not prevent STx release.
#55. A novel compound was developed which occupies the site on STx where GPP130 binds the toxin. A drug with which value of Kd for binding to STx is most effective?
--because in order to be a feasible option, the Kd for the compound and STx must be below the Kd of STx and GPP130. The lower the Kd of the drug, the more effective it will be at inhibiting the interaction between STx and GPP130 because it will bind to STx instead of STx binding to GPP130
#56. What type of enzyme is responsible for activating subunit A?
--Because subunit A is part of polypeptide chain that is subject to hydrolytic cleavage. This reaction is most likely catalyzed by a protease
An enzyme that breaks down proteins and peptides
An enzyme that cleaves a polynucleotide chain by separating nucleotides other than the two end ones
An enzyme that removes successive nucleotides from end of a polypeptide nucleotide
Another term for RNase
An enzyme that promotes the breakdown of RNA into oligonucleotides and smaller molecules
#57. Given the information in the table, are CAP and LacI transcription activators or trascription repressors?
look at the image
CAP is a transcription activator, and LacI is a transcription repressor
THIS QUESTION WAS MAD EASY!! DONT GET INTIMIDATED BY LONG QEUSTIONS. THEY JUST APPEAR CONFUSING BUT ARE SUPER EASY
#58. Introduction of which amino acid substitution would result in the largest decrease in the entropic penalty associated with a protein folding into its native conformation?
A. Ile to Asp substitution at a buried site
B. Leu to Thr substitution at a surface exposed site
C. Gly to Pro substitution in a flexible loop
D. Arg to Tyr substitution at a surface exposed site
B. Leu to Thr substitution at a surface exposed site
Because changing a surface-exposed hydrophobic residue to more hydrophilic residue eliminates the entropic penalty ass w/ ordered water molecules around hydrophobic groups
#59. In humans, the lining of which structure is NOT primarily derived from the endoderm?