Altius FL 2 Bio/Biochem Flashcards
Given a genome content of 50% AT, and assuming random nucleotide variability, the probability of the AUUUA sequence is one in every:
Correct. If 100 percent then 1/2, so note how probability plays a role here.
Based on the amount of KLF6 mRNA expressed after treatment with actinomycin D (Figure 2), cell lines derived from liver carcinomas exhibit:
Wrong. Asking to think how the effect of something being removed, what does it do to the remaining ones that are available
7.) Researchers used the following assay to investigate whether the TRAF6 protein is required for the dissociation of IκB from NF-κB. The impact of TRAF6 on two kinases of the IκB-NF-κB dissociation pathway was measured. β-actin was included in the assay in order to:
Answer choice A is correct. The assay shown is a Western blot, and β-actin was used as a loading control. In a Western blot, researchers are usually trying to measure the expression of a protein, or the amount of a protein product. Students should recall that the proteins in the original tissue sample must first be separated by electrophoresis. If, during this step, an unequal amount of sample is loaded into each lane, the resulting Western blot could show a smaller signal in a given lane, NOT because there was less of the protein being studied, but simply because less sample was loaded. For this reason, a structural protein such as β-actin (that is not affected by any of the treatments) is used as a control. This allows confirmation on the final blot that all lanes contained equal samples. Loading controls also allow researchers to verify that proteins were transferred equally from the gel to the blotting membrane. This makes Answer A correct. If the researchers wanted to ensure the same levels of HTLV-1 were in all samples, they would need to add an HTLV-1 antibody, eliminating Answer B. Based on passage information, and the fact that β-actin is never mentioned, it is highly unlikely that β-actin is involved in this process or being investigated by the researchers. Nothing in the passage suggests the virus affects actin molecules. Even if it did, to examine the impact of the virus on β-actin (degradation or overexpression) the researchers would need to compare b-actin in HTLV-1 cells to β-actin in a control cell line such as Jurkat. This is not seen in the Western blot. Rather, TRAF6 is being compared to a control. Therefore, Answers C and D are both incorrect.
9.) Where X represents the conjugate base, which of the acids listed is expected to have the smallest H-X bond dissociation energy?
First, the stronger the bond is between an acidic hydrogen and its conjugate base, the weaker that acid will be. Strong acids are expected to have relatively weaker H-X bonds (smaller bond dissociation energies) than weaker acids (larger bond dissociation energies). Second, a strong acid is defined by the extent to which it dissociates in water. A measure of its dissociation is its Ka, a type of equilibrium constant. pKa is defined as: pKa = –log Ka. The relationship between Ka and Kb is defined by the dissociation of water: Kw = 1 x 10-14 = KaKb. It therefore follows that pKw = 14 = pKa + pKb. This relationship is important so that the pKb values given in the answer choices can be converted to pKa values for direct comparison. Therefore, the pKa values in the list are: A) pKa = 4.10 (given); B) pKa = 4.75 (given); C) pKa = 14 – 9.63 = 4.37; D) pKa = 14 – 10.90 = 3.10. Since choice D has the smallest pKa value, it is the strongest acid and will be expected to have the weakest H-X bond. Much of this information is presented as background info for the student. If an examinee easily recognizes that C and D can be converted to pKa values, this question is as simple as picking the answer with the lowest pKa.
12.) A student attempts to isolate a solid organic drug compound with a known melting point range of 148-151 °F. An impure sample of this drug is likely to have which melting point range?
Impurities in a solid both depress the melting point, and broaden the range over which the solid melts. Impurities never increase the temperature at which the solid melts, so Answer B is eliminated. Answer A suggests that the melting point stays approximately the same, but the melting point range becomes more narrow. Just the opposite is caused by an impurity, so Answer A must be rejected. Answer C is false because, although the melting range is depressed as expected, the melting point range is more narrow than the range for the pure solid given in the stem. Answer D is correct because the melting point is depressed and the range over which the solid melts is broadened. As is often the case, the lower end of the melting point decreases significantly, while the upper end of the range changes very little, resulting in a net broadening of the melting range.
16.) Early-onset Familial Alzheimer’s Disease (EOFAD) is a rare autosomal dominant form of Alzheimer’s that causes symptoms as early as age 15. EOFAD is accompanied by typical senile plaques and is nearly indistinguishable from AD in elderly patients. How does this information relate to the two theories proposed to explain AD?
Wrong. It is about understanding the wording of the question. If something is age-related decline, that means that it will start at a later age. But if the question now states that it is early onset, that then contradicts the previous claim.
18.) Large stores of glycogen in skeletal muscle are critical during prolonged periods of exercise, because:
ATP is required as part of the sliding filament model of muscle contraction, which is obtained by hydrolyzing stored glycogen to generate glucose and then metabolizing that glucose. Specifically, hydrolysis of ATP is necessary to cock the myosin head, and the binding of ATP to the myosin head is necessary to release the myosin head from the actin filament in preparation for the following contraction cycle. Answer B is a true statement, but it is not the correct answer since polymerization of actin is not the reason large amounts of ATP are required during extended exercise. Answer C is not correct since muscle glycogen is not responsible for the regulation of blood sugar. Answer D confuses ATP with calcium and troponin/tropomysin. Under normal conditions, the myosin binding site located on the actin filament is covered by tropomyosin. When calcium binds troponin, troponin undergoes structural changes that move tropomyosin, exposing the binding site.
21.) Following ingestion of a meal high in simple carbohydrates, the primary metabolic process at work is:
Glycogenesis is the process of building glycogen to store glucose for the future. Answer A is one of the ways to consume glucose from the blood stream. Glycolysis only consumes a small amount of glucose prior to the pathway being shut down because the cell has sufficient energy. Because glycolysis consumes such a small amount of glucose prior to shutting down, it is not a major player in the balancing of blood sugar. Glycogen can grow to any size and therefore Answer D plays a much larger role in balancing blood sugar. Answers B and C are not correct since both of these processes will result in increased blood sugar since glucose is released from the cell.
24.) Researchers wondered if ResV could improve age-related decreases in heart function to mimic the level of function observed in young mice. To explore this possibility, they administered high doses of ResV to old mice. For this study, researchers most likely used mice from which group as a control?
Wrong. The interpretation of this is that, if I give something to someone and i want to measure the effect, how do I compare it? To the one without an intervention or the result?
29.) Which mutation would represent an oncogenic activation of Ras if the normal Ras mRNA sequence is the one shown below?
Wrong. Easy one to give away. Although I grasped the concept, I did not realize and I forgot that the key is to pick the one that
31.) The primary mRNA transcript for dystrophin contains 300,000 fewer nucleotides than the DMD gene from which it is transcribed. The primary mRNA transcript is shorter because:
Wrong. The trick here is to realize that primary transcript means the first one that is transcribed NOT the mature transcript adn that is the trick here in this case.
32.) The average protein is composed of approximately 500 amino acids. This suggests that the average mature mRNA polymer contains approximately:
Wrong. The trick here is to recognize that apart from a translated region, there is the need to recognize the fact that
34.) Which of the following is the MOST likely explanation for the greater severity of Duchenne muscular dystrophy compared to Becker muscular dystrophy?
Tricky question framing. The key here is to realize what is said in the difference between them and that was in the molecular basis and given in the passage. Go from there to make my answers.
56.) S. aureus has a generation time of 20 min. If biofilm density is proportional to colony size, which value gives the optical density (OD560) of the biofilm formed by the SBY2 colony one hour after the measurements taken for Figure 2?
Wrong. My own mistake. It was critical to understanding the meaning of the two concepts and why they were placed there. This was my own interpretation issue.
