Block 9 B & T Cell Bio Microb Growth Metab MCQ's
T/B cell biology; Microbe growth and metabolism; Replication, transcription and translation
- 1.
Humoral immunity can be acquired passively by
- A.
Receiving serum from someone who has recovered from an infection
- B.
Receiving a vaccine of influenza virus grown in eggs
- C.
Catching a virus from a friend by shaking hands.
- D.
Receiving leukocytes from an immune family member.
Correct Answer
A. Receiving serum from someone who has recovered from an infectionExplanation
Passive acquisition of humoral immunity refers to the transfer of pre-formed antibodies from one individual to another. When someone recovers from an infection, their body produces antibodies specific to that particular pathogen. By receiving the serum from this individual, the recipient gains temporary immunity as the transferred antibodies can recognize and neutralize the pathogen. This method is commonly used in the treatment of certain viral infections or to provide temporary protection against diseases. The other options mentioned in the question do not involve the transfer of antibodies and therefore do not contribute to passive acquisition of humoral immunity.Rate this question:
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- 2.
Cytotoxic T lymphocytes (CTL) recognize antigenic peptides presented by:
- A.
Adhesion molecules
- B.
MHC-II
- C.
MHC-I
- D.
Chemokine receptors
Correct Answer
C. MHC-IExplanation
Cytotoxic T lymphocytes (CTL) recognize antigenic peptides presented by MHC-I molecules. MHC-I molecules are found on the surface of almost all nucleated cells and they present peptides derived from intracellular antigens. CTLs have T cell receptors that can specifically bind to these antigenic peptides when they are presented on MHC-I molecules. This recognition is important for CTLs to identify infected or abnormal cells and initiate immune responses against them.Rate this question:
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- 3.
A fundamental difference between the antigen receptors on B cells (BCR) and receptors on T cells (TCR) is that
- A.
BCRs belong to the immunoglobulin superfamily while TCRs do not.
- B.
TCRs are MHC restricted while BCRs are not.
- C.
TCRs have the same specificity on all T cells while B cells have BCRs of only one specificity.
- D.
BCRs bind to carbohydrates while TCRs bind to peptides.
Correct Answer
B. TCRs are MHC restricted while BCRs are not.Explanation
The explanation for the given correct answer is that TCRs (receptors on T cells) are MHC (major histocompatibility complex) restricted, meaning they can only recognize antigens when they are presented by MHC molecules on the surface of other cells. On the other hand, BCRs (antigen receptors on B cells) are not MHC restricted, and they can directly recognize antigens without the need for MHC presentation. This fundamental difference in antigen recognition mechanisms is what sets TCRs apart from BCRs.Rate this question:
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- 4.
Antibody against CD56 is most likely to influence the function of which of the following cell types?
- A.
T lymphocytes
- B.
Macrophages
- C.
Natural killer cells
- D.
B-lymphocytes
- E.
Eosinophils
Correct Answer
C. Natural killer cellsExplanation
An antibody against CD56 is most likely to influence the function of natural killer cells. CD56 is a surface marker that is predominantly expressed on natural killer cells. Antibodies against CD56 can bind to and potentially inhibit the function of these cells, which are important for the immune response against viral infections and tumor cells. The other cell types listed, such as T lymphocytes, macrophages, B-lymphocytes, and eosinophils, do not typically express CD56 and would not be directly affected by an antibody against it.Rate this question:
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- 5.
Although DC generally are strong activators of T lymphocytes by way of their natural capacity to express co-stimulatory molecules, there are instances requiring CD4+ T lymphocyte help in order to achieve complete CD8+ T lymphocyte activation during some viral infections. What is the nature of CD4+ T lymphocyte help?
- A.
1L-4 stimulation of CD8+ T lymphocytes
- B.
1L-3 stimulation of CD8+ T lymphocytes
- C.
IL-1 stimulation of CD8+ T lymphocytes
- D.
1L-2 stimulation of CD8+ T lymphocytes
- E.
IL-6 stimulation of CD8+ T lymphocytes
Correct Answer
D. 1L-2 stimulation of CD8+ T lymphocytesExplanation
CD4+ T lymphocyte help is achieved through IL-2 stimulation of CD8+ T lymphocytes. This cytokine plays a crucial role in the activation and proliferation of CD8+ T cells, enhancing their cytotoxic function and promoting their survival. IL-2 is produced by activated CD4+ T cells and acts as a growth factor for CD8+ T cells, allowing them to reach their full activation potential. Therefore, IL-2 stimulation is necessary for complete CD8+ T lymphocyte activation during certain viral infections.Rate this question:
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- 6.
For naive CD4+ T lymphocytes to commit to a TH1 response, they require several signals. What are they?
- A.
MHC class I antigen presentation, CD80/CD86 co-stimulation and 1L-12
- B.
MHC class I antigen presentation, CD80/CD66 co-stimulation and 1L-4
- C.
MHC class II antigen presentation, CD80/CD86 co-stimulation and 1L-4
- D.
MHC class II antigen presentation, CD40 co-stimulation and 1L-4
- E.
MHC class II antigen presentation, CD80/CD86 co-stimulation and 1L-12
Correct Answer
E. MHC class II antigen presentation, CD80/CD86 co-stimulation and 1L-12Explanation
Naive CD4+ T lymphocytes require MHC class II antigen presentation, CD80/CD86 co-stimulation, and IL-12 signals to commit to a TH1 response. MHC class II antigen presentation is necessary for the T lymphocytes to recognize and bind to antigens presented by antigen-presenting cells. CD80/CD86 co-stimulation provides the second signal required for T cell activation and proliferation. IL-12 is a cytokine that promotes the differentiation of naive T cells into TH1 cells, which are involved in cell-mediated immune responses. Therefore, these signals are crucial for the commitment of naive CD4+ T lymphocytes to a TH1 response.Rate this question:
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- 7.
DiGeorge Syndrome is a primary immunodeficiency caused by a deletion in part of chromosome 22. In these patients, the thymic epithelium fails to develop normally leading to hypoplasia or aplasia of the thymus. What would you expect the phenotype of these patients to be?
- A.
Lack CD4 T cells
- B.
Lack CD8 T cells
- C.
Lack all T cells
- D.
Lack B cells
- E.
Normal numbers of T cells but increased numbers of self-reactive T cells
Correct Answer
C. Lack all T cellsExplanation
Patients with DiGeorge Syndrome have a deletion in part of chromosome 22, which leads to abnormal development of the thymic epithelium and results in hypoplasia or aplasia of the thymus. The thymus is responsible for the maturation of T cells, so in these patients, the absence or underdevelopment of the thymus would lead to a lack of all T cells. This would result in a primary immunodeficiency, as T cells play a crucial role in the immune response.Rate this question:
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- 8.
A 4-month old child is referred to a specialist because she has had recurrent severe infections, chronic diarrhea and failure to thrive. Her lymphocyte counts are low, and a detailed analysis reveals that she has normal numbers of CD8 T cells, but very low numbers of CD4 T cells. Failure to express which of the following would potentially lead to this phenotype?
- A.
RAG-1 and RAG-2
- B.
MHC Class I
- C.
MHC Class II
- D.
CD28
- E.
IL-2
Correct Answer
C. MHC Class IIExplanation
The given scenario describes a 4-month old child with recurrent severe infections, chronic diarrhea, and failure to thrive. The child's lymphocyte counts are low, and a detailed analysis reveals low numbers of CD4 T cells but normal numbers of CD8 T cells. MHC Class II molecules are responsible for presenting antigens to CD4 T cells, which are crucial for the activation of immune responses. Therefore, failure to express MHC Class II molecules would potentially lead to a decreased number of CD4 T cells and impaired immune response, resulting in the observed phenotype.Rate this question:
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- 9.
B and T cell receptors generate diversity in roughly similar ways. Which of the following is not common to both B and T cell receptors?
- A.
The use of V region genes
- B.
Somatic hypermutation
- C.
The use of terminal deoxynucleotidyl transferease
- D.
The expression of recombination activation genes
Correct Answer
B. Somatic hypermutationExplanation
Both B and T cell receptors generate diversity through the use of V region genes and the expression of recombination activation genes. However, somatic hypermutation is a process specific to B cell receptors, not T cell receptors. Somatic hypermutation is a mechanism that introduces random mutations in the variable region of B cell receptors, leading to the generation of a diverse repertoire of antibody molecules with different antigen-binding specificities. This process allows B cells to produce antibodies that can recognize a wide range of antigens. T cell receptors, on the other hand, do not undergo somatic hypermutation.Rate this question:
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- 10.
Natural killer cells (NK cells) are important in innate immunity and have which key functions?
- A.
As a subset of T lymphocytes, binding specific microbes with release of perforins and interferon-y
- B.
Through binding to MHC class I, killing infected cells by the killing activator receptor (KAR)
- C.
Through the CD 16 receptor, binding IgG and phagocytosing microbes
- D.
KiIling infected cells by antibody dependent cellular cytotoxcity (ADCC) through the FcyRIII receptor
Correct Answer
D. KiIling infected cells by antibody dependent cellular cytotoxcity (ADCC) through the FcyRIII receptorExplanation
Natural killer cells (NK cells) are a type of lymphocyte that play a crucial role in innate immunity. They are able to recognize and kill infected cells through a process called antibody-dependent cellular cytotoxicity (ADCC). This occurs when NK cells bind to antibodies that have attached to infected cells, activating the FcyRIII receptor on the NK cell. This activation triggers the release of cytotoxic granules, which contain proteins such as perforin and interferon-y, leading to the destruction of the infected cells. This mechanism allows NK cells to eliminate infected cells and contribute to the body's defense against pathogens.Rate this question:
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- 11.
T lymphocytes are subdivided into CD4+ T cells and CD8+ T cells. CD4+ T cells, or, helper T cells, are further subdivided into Th1 and Th2 cells by which manner?
- A.
Th2 cells develop under the influence of IL-12 to secrete IL-2 and interferon-y
- B.
Th2 cells develop under the influence of IL-2 to effect allergic reactions
- C.
Th1 cells develop under the influence of IL-4 to effect antibody formation
- D.
Th1 cells develop under the influence of IL-12 to drive cell-mediated immune responses
Correct Answer
D. Th1 cells develop under the influence of IL-12 to drive cell-mediated immune responsesExplanation
Th1 cells develop under the influence of IL-12 to drive cell-mediated immune responses. This means that IL-12 plays a role in the development of Th1 cells, which are a subset of CD4+ T cells. Th1 cells are responsible for promoting cell-mediated immune responses, such as activating macrophages and cytotoxic T cells, which are important for eliminating intracellular pathogens. IL-12 helps to drive the differentiation of naïve CD4+ T cells into Th1 cells, allowing them to carry out their immune functions effectively.Rate this question:
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- 12.
Some mice have been developed that cannot produce the molecule B2 microglobulin. What will happen to the T cells of these mice as they undergo selection in the thymus?
- A.
They will fail to develop any T cells
- B.
As they still can produce T cells thymic selection will be unaffected
- C.
They cannot produce CD4+ T cells
- D.
They cannot produce CD8+ T cells
Correct Answer
D. They cannot produce CD8+ T cellsExplanation
β2 microglobulin also known as B2M is a component of MHC class I molecules, which are present on all nucleated cells (excludes red blood cells).
In patients on long-term hemodialysis, it can aggregate into amyloid fibers that deposit in joint spaces, a disease known as dialysis-related amyloidosis.
Mice models deficient for the β2 microglobulin gene have been engineered. These mice demonstrate that β2 microglobulin is necessary for cell surface expression of MHC class I and stability of the peptide binding groove. In fact, in the absence of β2 microglobulin, very limited amounts of MHC class I (classical and non-classical) molecules can be detected on the surface. In the absence of MHC class I, CD8 T cells cannot develop. (CD8 T cells are a subset of T cells involved in the development of acquired immunity.)Rate this question:
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- 13.
Both ADCC (antibody dependent cellular cytotoxicity) and opsonlzation involve antibodies. Which of the following would you consider to be differences between the two systems
- A.
Only ADCC involves the binding of antibody to a target cell
- B.
Only opsonization Involves phagocytes as the effector cell
- C.
Only opsonization is carried out using IgG and an FcyRIII on the effector cell.
- D.
Only ADCC relies on the ability of antibody to bind antigen and simultaneously attach to an effector cell.
Correct Answer
B. Only opsonization Involves phagocytes as the effector cellExplanation
Opsonization involves phagocytes as the effector cell, whereas ADCC does not. ADCC relies on the ability of antibody to bind antigen and simultaneously attach to an effector cell, whereas opsonization does not require this simultaneous attachment. Additionally, opsonization is carried out using IgG and an FcyRIII on the effector cell, while ADCC does not specifically require these components.Rate this question:
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- 14.
Laboratory evaluation of a patient's immunological status yields the following information: IgM=0.5 (0.3-1.8); IgG=1.5 (5.0-10.0); IgA=0.1 (0.2-1.0); CD3+ cells=0.5% (1.5-3.0); CD21+ cells=0,41% (0.1-0,5). Based on this information, which of the following statements is most correct regarding the patient's immune status?
- A.
The patients has a selective IgA deficiency
- B.
The patient has a low number of B cells
- C.
The patient has a low number of T cells
- D.
The patient has a low number of plasma cells
- E.
The patient has a deficiency of adenosine deaminase
Correct Answer
C. The patient has a low number of T cellsExplanation
The patient's laboratory results show a low percentage of CD3+ cells, which are a marker for T cells. T cells are a type of white blood cell that play a crucial role in the immune response. A low number of T cells indicates a compromised immune system, as T cells are responsible for recognizing and attacking foreign pathogens. Therefore, the statement that the patient has a low number of T cells is the most correct regarding the patient's immune status.Rate this question:
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- 15.
Why are NK cells so important in the control of viruses during the initial stages of infection?
- A.
They readily kill complement opsonized viruses
- B.
They readily kill MHC-I-depleted infected cells
- C.
They readily kill antibody opsonized viruses
- D.
They readily kill MHC-II-depleted infected cells
- E.
They can directly activate CD8 T lymphocytes
Correct Answer
B. They readily kill MHC-I-depleted infected cellsExplanation
NK cells are important in the control of viruses during the initial stages of infection because they readily kill MHC-I-depleted infected cells. MHC-I molecules present viral antigens on the surface of infected cells, allowing them to be recognized and destroyed by CD8 T lymphocytes. However, some viruses have evolved mechanisms to downregulate MHC-I expression, evading CD8 T cell recognition. NK cells can recognize and kill these MHC-I-depleted infected cells, providing an important defense mechanism against viral infections.Rate this question:
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- 16.
The IgM and IgD expressed on an individual mature, naive B cell
- A.
Have identical heavy chains but different light chains
- B.
Have identical variable regions but different constant regions on their heavy chains
- C.
Have identical constant regions but different variable regions on their heavy chains
- D.
Have identical variable regions but different constant regions on their light chains
- E.
Have different variable regions on both the light and heavy chains
Correct Answer
B. Have identical variable regions but different constant regions on their heavy chainsExplanation
The IgM and IgD expressed on an individual mature, naive B cell have identical variable regions but different constant regions on their heavy chains. This means that the part of the antibody that recognizes and binds to antigens (variable region) is the same for both IgM and IgD, but the part that determines the function and location of the antibody (constant region) is different. This allows the B cell to produce different types of antibodies with different functions while still recognizing the same antigens.Rate this question:
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- 17.
Which of the following nutrients is sequestered by the mammalian system as a protective mechanism and is often the rate-limiting nutrient for bacterial growth?
- A.
Selenium
- B.
Glucose
- C.
Fatty acids
- D.
Molybdenum
- E.
Iron
Correct Answer
E. IronExplanation
Iron is sequestered by the mammalian system as a protective mechanism and is often the rate-limiting nutrient for bacterial growth. Iron is essential for the growth and survival of bacteria, so the mammalian system sequesters iron to limit its availability to bacteria and prevent their proliferation. This is a protective mechanism to inhibit bacterial growth and prevent infections.Rate this question:
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- 18.
What macromolecule is used by bacteria to sequester that nutrient?
- A.
Superoxide disrnutase
- B.
Allosteric protein inhibitors
- C.
Transrnembrane proteins
- D.
Peptidoglycan
- E.
Siderophores
Correct Answer
E. SiderophoresExplanation
Mamallian cells use Ferritin
-Siderophores- are small, high-affinity iron chelating compounds secreted by grasses and MICROORGANISMS such as bacteria and fungi. Siderophores are amongst the strongest soluble Fe3+ binding agents known.
FUN FACT (not testable)
Siderophores have applications in medicine for iron and aluminum overload therapy and antibiotics for better targeting. Understanding the mechanistic pathways of siderophores has led to opportunities for designing small-molecule inhibitors that block siderophore biosynthesis and therefore bacterial growth and virulence in iron-limiting environments.
Siderophores are useful as drugs in facilitating iron mobilization in humans, especially in the treatment of iron diseases, due to their high affinity for iron. One potentially powerful application is to use the iron transport abilities of siderophores to carry drugs into cells by preparation of conjugates between siderophores and antimicrobial agents. Because microbes recognize and utilize only certain siderophores, such conjugates are anticipated to have selective antimicrobial activity.
Microbial iron transport (siderophore)-mediated drug delivery makes use of the recognition of siderophores as iron delivery agents in order to have the microbe assimilate siderophore conjugates with attached drugs. These drugs are lethal to the microbe and cause the microbe to apoptosise when it assimilates the siderophore conjugate. Through the addition of the iron-binding functional groups of siderophores into antibiotics, their potency has been greatly increased. This is due to the siderophore-mediated iron uptake system of the bacteriaRate this question:
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- 19.
What is the phase of bacterial growth called when the following happens: the cells start to die and new growth slows
- A.
Death phase
- B.
Logarithmic phase
- C.
Stationary phase
- D.
Lag phase
Correct Answer
C. Stationary phaseExplanation
During lag phase, bacteria adapt themselves to growth conditions. It is the period where the individual bacteria are maturing and not yet able to divide. During the lag phase of the bacterial growth cycle, synthesis of RNA, enzymes and other molecules occurs.
2. Exponential phase (sometimes called the log phase or the logarithmic phase) is a period characterized by cell doubling. The number of new bacteria appearing per unit time is proportional to the present population. If growth is not limited, doubling will continue at a constant rate so both the number of cells and the rate of population increase doubles with each consecutive time period. For this type of exponential growth, plotting the natural logarithm of cell number against time produces a straight line. The slope of this line is the specific growth rate of the organism, which is a measure of the number of divisions per cell per unit time. The actual rate of this growth (i.e. the slope of the line in the figure) depends upon the growth conditions, which affect the frequency of cell division events and the probability of both daughter cells surviving. Under controlled conditions, cyanobacteria can double their population four times a day. Exponential growth cannot continue indefinitely, however, because the medium is soon depleted of nutrients and enriched with wastes.
3. During stationary phase, the growth rate slows as a result of nutrient depletion and accumulation of toxic products. This phase is reached as the bacteria begin to exhaust the resources that are available to them. This phase is a constant value as the rate of bacterial growth is equal to the rate of bacterial death.
4. At death phase, bacteria run out of nutrients and die.Rate this question:
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- 20.
Because environmental conditions can change rapidly in the microbial world, the bacteria require a rapid change in gene expression in order to survive and, ultimately, to cause disease in the host. What molecules do the bacteria express and release that allows the allows the bacteria to be aware of the density their species in the environment, thus enabling the bacteria to coordinate their expression of specific virulence genes; in addition, what level do these molecules need to reach in order for this gene expression to occur.
- A.
Signal molecules, low density
- B.
Signal molecules, high density
- C.
Siderophores, low density
- D.
M protein, high density
- E.
Protein A, low density
Correct Answer
B. Signal molecules, high densityExplanation
Bacteria express and release signal molecules that allow them to be aware of the density of their species in the environment. When the density of these signal molecules reaches a high level, it triggers the bacteria to coordinate the expression of specific virulence genes. This rapid change in gene expression is necessary for the bacteria to survive and cause disease in the host. Therefore, the correct answer is "Signal molecules, high density."Rate this question:
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- 21.
During chromosomal replication in a typical bacterium, which of the following best describes the enzymatic activity of DNA ligase?
- A.
Breaks hydrogen bonds between complementary nucleotides
- B.
Synthesizes short DNA molecules important for the function of DNA polymerase
- C.
Seals gaps between DNA fragments
- D.
Proofreads DNA molecules
- E.
Assists in recognition of promoters during transcription
Correct Answer
C. Seals gaps between DNA fragmentsExplanation
DNA ligase is an enzyme that plays a crucial role in the process of DNA replication. It is responsible for sealing gaps between DNA fragments by catalyzing the formation of phosphodiester bonds between adjacent nucleotides. This helps to create a continuous and intact DNA strand. Therefore, the correct answer is that DNA ligase seals gaps between DNA fragments.Rate this question:
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- 22.
During translation, an mRNA codon will pass through which of the following sequences of tRNA binding sites on the ribosome:
- A.
A site, E site, P site
- B.
E site, P site, A site
- C.
P site, E site, A site
- D.
A site, P site, E site
- E.
P site, A site, E site
Correct Answer
D. A site, P site, E siteExplanation
spells: APERate this question:
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- 23.
Which of the following is the secretion system of Gram-negative bacteria involved in secretion of virulence factors and is homologous to the bacterial flagellar basal body?
- A.
The Type IV secretion system
- B.
The Type II secretion system
- C.
The Autotransporter secretion system (type V)
- D.
The Type III secretion system
- E.
The Sec YGE secretion system
Correct Answer
D. The Type III secretion systemExplanation
http://en.wikipedia.org/wiki/Secretion#Type_IV_secretion_system_.28T4SS_or_TFSS.29Rate this question:
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- 24.
The OmpR response regulator is activated in the presence of high solutes. One of the genes activated by OmpR is micF, whose product binds the ompF message and ends up reducing OmpF protein production, thereby reducing solute uptake. Which of the following terms would best describe micF and the stage at which it regulates OmpF production?
- A.
An antiterminator, acts on transcription
- B.
An RNA stabilizing protein, alters translation
- C.
An antisense RNA, alters translation
- D.
A kinase, regulates post-translationally
- E.
A sigma factor, acts on transcription
Correct Answer
C. An antisense RNA, alters translationExplanation
MicF is an antisense RNA that regulates OmpF protein production by binding to the ompF message. This binding leads to a reduction in OmpF protein production, thereby reducing solute uptake. Antisense RNA molecules bind to their target mRNA and can interfere with translation, altering the production of the corresponding protein. Therefore, the term "an antisense RNA, alters translation" best describes micF and the stage at which it regulates OmpF production.Rate this question:
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- 25.
Analysis of a mucosal epithelial cell toxin produced by a pathogenic Gram-negative bacterium suggests that: (1) The toxin does not have a periplasmic intermediate and that (2) it does not appear in the extracellular milieu, but instead appears directly in the target host cell. The genes encoding proteins important in the production of this toxin appear to be on a pathogenicity island. Which type of secretion is most likely to release this toxin from the bacterial cell?
- A.
A Type 1 ATP-dependent secretion system
- B.
A Type mian terminal branch secretion system
- C.
A Type III injectsome secretion system
- D.
A Type IV secretion system
- E.
A Type V autotransporter secretion system
Correct Answer
C. A Type III injectsome secretion systemExplanation
http://en.wikipedia.org/wiki/Secretion#Type_IV_secretion_system_.28T4SS_or_TFSS.29Rate this question:
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- 26.
The T cell receptor (TCR)/CD3 complex can be considered to consist of four molecular dimmers. What are these dimmers?
- A.
The TCR, ge, de & zz of CD3
- B.
The TCR, gd, ee & zz of CD3
- C.
The TCR, ge, de & hh of CD3
- D.
The TCR, gd,ee & hh of CD3
Correct Answer
A. The TCR, ge, de & zz of CD3Explanation
The T cell receptor (TCR)/CD3 complex consists of four molecular dimers, specifically the TCR, ge, de, and zz of CD3. These four dimers come together to form the complex, which plays a crucial role in the activation and signaling of T cells. Each dimer contributes to the overall structure and function of the TCR/CD3 complex, allowing for the recognition and response to antigens.Rate this question:
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