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Biochemistry & Cell Biology

Latest questions in this category.

25 questions

Biochemistry & Cell Biology

Chain is present in which antibodies (DROP)

This question was marked DROP due to ambiguity regarding which chain was intended. If referring to gamma heavy chain, it defines IgG isotype. J chain actually occurs in polymeric IgM and IgA, not IgG. The intended answer was recorded as IgG, but the item was subsequently withdrawn from scoring.

Ref: Owen et al., Kuby Immunology, 8th Edition, Chapter 5, discusses immunoglobulin heavy chain isotypes, gamma chain for IgG, mu for IgM, J chain association with polymers and antibody structure classification, published by W.H. Freeman.

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Biochemistry & Cell Biology

The class of an immunoglobulin

Immunoglobulin class or isotype is defined by heavy chain constant region: mu for IgM, delta for IgD, gamma for IgG, alpha for IgA, epsilon for IgE. Each isotype confers distinct effector functions, localization and half-life, independent of antigen specificity or light chains.

Ref: Owen et al., Kuby Immunology, 8th Edition, Chapter 5, describes immunoglobulin structure, heavy chain isotypes, class determination, constant region genes and isotype-specific effector functions, published by W.H. Freeman and Company.

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Biochemistry & Cell Biology

Opsonin is the

Opsonins are serum proteins such as IgG and complement C3b that coat pathogens, enhancing phagocytosis via Fc and complement receptors. They act as bridges between microbe and phagocyte, increasing efficiency of clearance. Present in serum, not cell wall or cytoplasmic compartments.

Ref: Murphy and Weaver, Janeway's Immunobiology, 9th Edition, Chapter 3, covers complement system, opsonization by C3b and antibodies, phagocytosis enhancement and serum components mediating innate immunity, published by Garland Science.

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Biochemistry & Cell Biology

B cells differentiate to form

Activated B cells in germinal centers undergo clonal expansion, somatic hypermutation and class switching, differentiating into antibody-secreting plasma cells for immediate protection and long-lived memory B cells that mount rapid recall responses upon secondary antigen encounter.

Ref: Owen et al., Kuby Immunology, 8th Edition, Chapter 11, discusses B cell activation, germinal center reaction, plasma cell differentiation, memory B cell formation and humoral immune memory, published by W.H. Freeman.

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Biochemistry & Cell Biology

Cell-mediated immunity

Cell-mediated immunity defends against intracellular pathogens through cytotoxic T lymphocytes, TH1 cells, activated macrophages and cytokines like IL-2 and IFN-gamma. Unlike humoral immunity, it cannot be transferred by serum but by T cells, and represents adaptive rather than innate response.

Ref: Abbas et al., Cellular and Molecular Immunology, 10th Edition, Chapter 11, explains cell-mediated immunity, T cell-macrophage interactions, interleukin signaling, cytotoxicity and delayed-type hypersensitivity mechanisms, published by Elsevier.

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Biochemistry & Cell Biology

A tissue graft between two people who are not genetically identical is termed a

Grafts within same species but genetically distinct individuals are called allografts, previously termed homografts. Survival depends on MHC compatibility. Isograft is between identical twins, xenograft across species, autograft within same individual. Allograft rejection involves T cell recognition of alloantigens.

Ref: Murphy and Weaver, Janeway's Immunobiology, 9th Edition, Chapter 14, discusses transplantation immunology, graft classifications, allograft, isograft, xenograft definitions and MHC-mediated rejection mechanisms, published by Garland Science.

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Biochemistry & Cell Biology

Acute inflammation characteristically involves?

Acute inflammation is dominated by rapid neutrophil recruitment within minutes to hours, mediated by histamine, complement C5a and IL-8. Neutrophils phagocytose microbes and release reactive oxygen species. Macrophages predominate later in chronic inflammation, while mast cells initiate but do not influx.

Ref: Abbas et al., Cellular and Molecular Immunology, 10th Edition, Chapter 4, covers innate immunity, acute inflammatory response, neutrophil chemotaxis, vascular changes and inflammatory mediators, published by Elsevier.

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Biochemistry & Cell Biology

Type I hypersensitivity is mediated by which of the following immunoglobulins?

Type I immediate hypersensitivity involves IgE binding to Fc epsilon RI on mast cells and basophils. Cross-linking by allergen triggers degranulation, releasing histamine, leukotrienes and cytokines causing allergy, asthma and anaphylaxis. IgE levels rise during allergic sensitization.

Ref: Owen et al., Kuby Immunology, 8th Edition, Chapter 15, explains hypersensitivity classification, Type I IgE-mediated mechanisms, mast cell degranulation, allergic inflammation and anaphylaxis pathogenesis, published by W.H. Freeman and Company.

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Biochemistry & Cell Biology

Which of the following is the major immunoglobulin in human serum, accounting for 80% of the immunoglobulin pool?

IgG dominates human serum, constituting roughly 75-80% of total immunoglobulins. It is monomeric, longest half-life (~21 days), crosses placenta, opsonizes pathogens and activates complement via classical pathway. Its abundance reflects secondary immune responses and memory establishment.

Ref: Murphy and Weaver, Janeway's Immunobiology, 9th Edition, Chapter 5, details immunoglobulin classes, serum concentrations, IgG abundance, structure, placental transfer and effector functions, published by Garland Science.

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Biochemistry & Cell Biology

Which of the following substance will not stimulate an immune response unless they are bound to a large molecule?

Haptens are small molecules like drugs or dinitrophenol that are not immunogenic alone because they cannot be presented efficiently. When conjugated to carrier proteins such as albumin, they form hapten-carrier complexes that elicit specific antibody responses, a principle used in immunization and allergy.

Ref: Owen et al., Kuby Immunology, 8th Edition, Chapter 3, discusses antigens, haptens, carrier proteins, immunogenicity requirements and hapten-carrier conjugates for antibody induction, published by W.H. Freeman and Company.

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Biochemistry & Cell Biology

Which of the following cannot be used to analyse unstained biological samples?

Unstained living cells are examined by phase-contrast, dark-field or fluorescence without chemical staining. Antibody-based detection inherently requires labeled secondary antibodies or chromogenic reactions that constitute immunostaining. Without staining or tagging, antibodies alone cannot visualize structures in phase contrast microscopy.

Ref: Murphy and Weaver, Janeway's Immunobiology, 9th Edition, Chapter 20, Appendix, explains immunohistochemistry, antibody labeling techniques, immunofluorescence and necessity of staining for antibody-based sample analysis, published by Garland Science.

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Biochemistry & Cell Biology

Wavelength range of absorption for a peptide bond is

The peptide bond possesses pi to pi* and n to pi* transitions absorbing strongly between 190-230 nm, with maximum near 190-195 nm and weaker shoulder near 210-220 nm. This far-UV absorption is exploited to quantify protein backbone concentration independent of aromatic side chains.

Ref: Nelson and Cox, Lehninger Principles of Biochemistry, 7th Edition, Chapter 3, discusses amino acids and peptides, peptide bond spectroscopic properties, UV absorption ranges for backbone and aromatic residues, published by W.H. Freeman.

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