EBOV and clathrin-mediated endocytosis
- Dashboard
- EBOV and clathrin-mediated endocytosis
Most Recent Score Report
| Questions Correct | Questions Answered | Time Spent | Status | Attempt Date | |
|---|---|---|---|---|---|
| -- | -- | -- | -- | -- |
Previous Score Reports
| Questions Correct | Questions Answered | Time Spent | Status | Attempt Date | |
|---|---|---|---|---|---|
| -- | -- | -- | -- | -- |
EBOV and clathrin-mediated endocytosis
Array
(
[passage] => WP_Post Object
(
[ID] => 554574
[post_author] => 12815
[post_date] => 2024-12-23 17:52:36
[post_date_gmt] => 2024-12-23 22:52:36
[post_content] => Practice Passage (Question 1-6)
*This passage is the property of Khan Academy and has been reformatted into an AAMC-style interface in their entirety by MedLife Mastery. MedLife Mastery does not endorse and is not an affiliate of Khan Academy.
The Zaire ebolavirus (EBOV) is a negative-sense, single-stranded RNA virus composed of a helical RNA strand bound by several structural and regulatory proteins, including VP35, VP30, nucleoprotein (NP) and protein L, contained within the capsid. VP35 and VP30 are cofactors of protein L, which catalyzes the transcription of viral RNA within the cytosol of the host cell. The capsid is surrounded by an envelope derived from the host cell’s plasma membrane, which is studded with 10 nm spikes of viral glycoprotein (GP). Unlike positive-sense RNA viruses, such as poliovirus, the pure, isolated RNA from EBOV is not inherently infectious, because it must first be transcribed to produce functional viral mRNA. In comparison, the viral genome of poliovirus and other positive-sense pathogens can be immediately translated by the host cell into necessary viral proteins. The structure of EBOV is shown in Figure 1.
Figure 1 Structure of EBOV
Researchers were interested in investigating whether the mechanism of cell entry of EBOV differs from clathrin-mediated endocytosis, which is the mechanism used by many positive-sense RNA viruses like poliovirus. To investigate this, they separated 200 rats into two even groups. They infected group-1 rats with live poliovirus and group-2 rats with live EBOV. For each group, half of the rats were then injected with “drug X”, a drug known to inhibit dynamin. After two weeks, biopsies were taken, and immunohistochemical staining was used to identify the number of infected cells per high-powered microscope field. The results are shown in Figure 2.
Figure 2 Effect of drug X on viral infectivity
[post_title] => EBOV and clathrin-mediated endocytosis
[post_excerpt] =>
[post_status] => publish
[comment_status] => closed
[ping_status] => closed
[post_password] =>
[post_name] => ebov-clathrin-mediated-endocytosis
[to_ping] =>
[pinged] =>
[post_modified] => 2024-12-23 17:52:36
[post_modified_gmt] => 2024-12-23 22:52:36
[post_content_filtered] =>
[post_parent] => 0
[guid] => https://medlifemastery.com/?post_type=passage&p=554574
[menu_order] => 0
[post_type] => passage
[post_mime_type] =>
[comment_count] => 0
[filter] => raw
)
[questions] => Array
(
[0] => Array
(
[quiz_unique_key] => 602779517
[question] => From the results in Figure 2, what can be concluded about EBOV’s mechanism of cell entry, and why?
[value] => Array
(
[answer] => 4
[description] => Reason for Correct Answer:
During clathrin-mediate endocytosis, the vesicle is pinched off by the action of dynamin, which progressively tightens around the budding vesicle like a belt, until it is entirely endocytosed.
Inhibition of dynamin by drug X therefore likely inhibits clathrin-mediated endocytosis. (This also makes sense because researchers were using Drug X to investigate whether EBOV, like poliovirus, uses clathrin-mediated endocytosis.)
Figure 1 indeed shows that infection with poliovirus, which uses clathrin-mediated endocytosis, is inhibited by drug X.
Drug X, however, does not affect the ability of EBOV to infect host cells – as there is no significant difference in EBOV infection in cells receiving the drug and cells not receiving the drug (control cells).
This suggests that EBOV infection does not depend on clathrin-mediated endocytosis.
)
[answers] => Array
(
[0] => Array
(
[each_answer] => A. EBOV probably enters the cell via clathrin-mediated endocytosis because no significant change in the number of infected cells is seen between the control group and the group receiving the drug.
)
[1] => Array
(
[each_answer] => B. EBOV probably enters the cell via clathrin-mediated endocytosis because the EBOV group treated with drug X shows a decrease in the percentage of infected cells.
)
[2] => Array
(
[each_answer] => C. EBOV probably does not enter the cell via clathrin-mediated endocytosis because the number of infected cells is significantly higher in the EBOV control group than in the poliovirus group.
)
[3] => Array
(
[each_answer] => D. EBOV probably does not enter the cell via clathrin-mediated endocytosis because no significant change in the number of infected cells is seen between the control group and the group receiving the drug.
)
)
)
[1] => Array
(
[quiz_unique_key] => 1403770772
[question] => An EBOV protein is translated from the hypothetical mRNA sequence shown. 
This means that the corresponding segment of the original viral genome had what nucleotide sequence?
[value] => Array
(
[answer] => 2
[description] => Reason for Correct Answer:
As the passage states, EBOV is a negative-sense RNA virus, which means it must be transcribed to mRNA before it can be translated into protein.
RNA polymerase reads negative-sense RNA in the 3’ → 5’ direction, synthesizing mRNA in the 5’ → 3’ direction.
So, this would be the corresponding sequence for the viral RNA genome:
Because the answer choices are provided in the 5’ → 3’ direction, the answer is 5’-UUACAGCCUAGG-3’.
)
[answers] => Array
(
[0] => Array
(
[each_answer] => A. 5’-GGAUCCGACAUU-3’
)
[1] => Array
(
[each_answer] => B. 5’-UUACAGCCUAGG-3’
)
[2] => Array
(
[each_answer] => C. 5’-GGATCCGACATT-3’
)
[3] => Array
(
[each_answer] => D. 5’-TTACAGCCTAGG-3’
)
)
)
[2] => Array
(
[quiz_unique_key] => 1403770772
[question] => The pure, isolated EBOV genome is transcribed immediately after entering the host cell. Considering the products of this transcription, the pure, isolated EBOV genome is analogous to which molecule?
[value] => Array
(
[answer] => 2
[description] => Reason for Correct Answer:
EBOV is a negative-sense RNA virus; this means that it must first transcribe its genome before protein synthesis can begin. Negative-sense RNA viruses have a genome that is read in the 3’ → 5’ direction, producing mRNA in the 5’ → 3’ direction.
tRNA is used in translation and does not code for other RNA, so it’s not similar in this context.
mRNA codes for proteins, not other RNA, so it’s also not similar in this context.
DNA consists of two strands. The coding, or sense strand, is similar to the sequence of the mRNA (in mRNA, T is replaced with U and the introns are cut out). The template, or antisense strand, is used to make mRNA.
https://www.genome.gov/genetics-glossary/antisense
Like negative-sense RNA, the antisense strand, or template strand, of DNA is read in the 3’ → 5’ direction to make mRNA in the 5’ → 3’ direction.
)
[answers] => Array
(
[0] => Array
(
[each_answer] => A. Coding DNA strand
)
[1] => Array
(
[each_answer] => B. Antisense DNA strand
)
[2] => Array
(
[each_answer] => C. tRNA
)
[3] => Array
(
[each_answer] => D. mRNA
)
)
)
[3] => Array
(
[quiz_unique_key] => 1403770772
[question] => What is the fate of clathrin-coated vesicles after they pinch off from the plasma membrane?
[value] => Array
(
[answer] => 1
[description] => Reason for Correct Answer:
Clathrin-coated vesicles are involved in endocytosis, a process by which cells take in substances from the external environment.
After the intake of these vesicles, the cell needs to degrade and process the materials that were taken in through endocytosis.
After they pinch off from the plasma membrane, these vesicles therefore often fuse with lysosomes, which contain various enzymes that can break down the contents of the vesicles.
)
[answers] => Array
(
[0] => Array
(
[each_answer] => A. They fuse with lysosomes for degradation.
)
[1] => Array
(
[each_answer] => B. They enter the endoplasmic reticulum.
)
[2] => Array
(
[each_answer] => C. They become part of the Golgi apparatus.
)
[3] => Array
(
[each_answer] => D. They are expelled from the cell through exocytosis.
)
)
)
[4] => Array
(
[quiz_unique_key] => 1403770772
[question] => Based on the information in the passage, what is another name for Protein L in EBOV?
[value] => Array
(
[answer] => 4
[description] => Reason for Correct Answer:
Protein L catalyzes the transcription of the viral genome to produce a strand that is capable of being translated by the host cell’s machinery.
According to the passage, this transcription product is analogous to a positive-sense virus’s genome, which is analogous to mRNA.
Transcription is catalyzed by RNA polymerase.
)
[answers] => Array
(
[0] => Array
(
[each_answer] => A. Reverse transcriptase
)
[1] => Array
(
[each_answer] => B. DNA helicase
)
[2] => Array
(
[each_answer] => C. DNA polymerase
)
[3] => Array
(
[each_answer] => D. RNA polymerase
)
)
)
[5] => Array
(
[quiz_unique_key] => 1115843717
[question] => Researchers combined purified VP30 with a section of radiolabeled RNA from EBOV. They analyzed this sample, along with a sample of radiolabeled EBOV RNA that was not exposed to VP30, using non-denaturing polyacrylamide gel electrophoresis (native PAGE). The gel was visualized using autoradiography. What is the relationship between the gel bands, and why?
[value] => Array
(
[answer] => 3
[description] => Reason for Correct Answer:
The first paragraph of the passage states that the RNA strand of EBOV is “bound by several structural and regulatory proteins, including VP35, VP30…”.
Though PAGE is most often used to analyze proteins, it can also be used to analyze RNA and RNA-protein interactions.
Non-denaturing PAGE is a technique that preserves intermolecular interactions and secondary structure. This is in contrast to denaturing PAGE (such as SDS-PAGE). RNA–protein interactions are therefore maintained during the experiment.
The question states that the RNA was radiolabeled and that the gel was visualized with autoradiography.
The mobility of a band (how fast it moves) is inversely proportional to its size (it is also directly proportional to its charge, but that is less important here). An RNA–protein complex will have a larger size than the RNA alone, and will therefore migrate slower.
)
[answers] => Array
(
[0] => Array
(
[each_answer] => A. Both bands run at the same speed because they are run under native conditions.
)
[1] => Array
(
[each_answer] => B. The VP30-RNA band runs faster than the RNA band because VP30 binds to RNA.
)
[2] => Array
(
[each_answer] => C. The VP30-RNA band runs slower than the RNA band because VP30 binds to RNA.
)
[3] => Array
(
[each_answer] => D. The RNA band is absent and the VP30-RNA is present because the RNA cannot be visualized.
)
)
)
)
[total_question] => 6
[correct_answers] => Array
(
[554574|1] => D
[554574|2] => B
[554574|3] => B
[554574|4] => A
[554574|5] => D
[554574|6] => C
)
[hide_display_feedback_settings] =>
[hide_solutions] =>
)
Figure 1
Figure 2
