A secreted IgM antibody is composed of: A. 2 peptide chains called heavy and lig
ID: 94975 • Letter: A
Question
A secreted IgM antibody is composed of: A. 2 peptide chains called heavy and light chains B. 3 peptide chains called heavy and light chains C. 4 peptide chains called heavy and light chains D. 2 complete antibody molecules joined by a J chain E. 5 complete antibody molecules joined When V, D, and J regions are joined: A. exact template DNA is used B. no mutation may occur or the antibody won't be produced C. DNA mismatches between the two DNA strands removed and refilled D. DNA mismatches between the two DNA strands are retained E. none of the above The endogenous presentation pathway requires: A. Phagocytosis B. Interaction with HLA-DM C. Removal of CLIP peptide D. Processing by the proteasome E. Presentation on MHC Class II Anchor residues have the following function: A. Hold antigens to antibodies B. Hold peptides in the T cell receptor C. Bind to CD4 molecules D. Bind to CD8 molecules E. Hold peptides in the MHC grooveExplanation / Answer
1. Immunoglobulin M is a specific type of antibody secreted by a plasma B cell. This is also the largest antibody in the human circulatory system, interestingly this comes as a first line of defense when cells are exposed to an antigen. Spleen produces the IgMs.
Its secretion is consists of a polymer, where the antibody molecules are joined by the covalent disulfide bond. It is occurring is mostly as pentamers, (5 linked immunoglobulins), also hexamers are present.
The correct answer choice here is E. 5 complete antibody molecules joined.
2. When V, D and J regions are joined occurs in the early lymphocyte formation. When there is unique sequences for the Igs (immuoglobulins) and T cell receptors are found on the B cell and T cells. This process produces unique antigen receptors. Occurring in bone marrow and thymus (primary lymphoid organs) in a nearly randomized fashion, joining the variable (V), Joining (J) and diversity (D) segments. The somatic recombination occurs, via the somatic hyper mutation and class-switch recombination, here point mutation takes place. The removal of DNA bases, as in the V and D regions are removed and then joined back to the DNA chain to form the functional ADJ recombination.
The answer for this whole process is C. DNA mismatches between the two DNA strands removed and refilled.
3. The endogenous presentation pathway talks about the antigen presented by the MHC class I, this is basically to process the antigen by the nucleated cells and show on the cell surface for CD8+ (cytotoxic T cell) cells to recognize.
Here the processing takes place by proteasome, so the right answer choice is D. Processing by the proteasome.
4. Peptide molecules from the antigens, processed by the MHC molecules are then binds to their surface by the primary and secondary anchor residues. They are attached to the MHCs, into their groove or pockets for peptide binding.
The right answer choice is E. Hold peptides in the MHC groove.
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