Chapter 12 with our Microbiology MCQs and explanations! Test your knowledge and understanding of key concepts with our complete set of multiple choice questions with detailed explanations for each answer. Increase your confidence and understanding of the fascinating world of microorganisms!
Microbiology MCQs 551 to 600
Enzymes are chemically?
- a) Lipids
- b) Proteins
- c) Carbohydrates
- d) None of these
Explanation:
Almost all enzymes are proteins. They are made up of long chains of amino acids folded into unique three-dimensional shapes that allow them to act as biological catalysts.
Why other options are incorrect:
Why other options are incorrect:
- • Lipids: These are fats and oils used for energy storage and cell membranes, not for catalytic functions.
- • Carbohydrates: These are sugars and starches used primarily for energy and structural support (like cellulose).
- • None of these: Since enzymes are proteins, this option is incorrect.
Monoclonal antibodies are produced by?
- a) Hybridoma technology
- b) Biotechnology
- c) Fermentation Technology
- d) None of these
Explanation:
Monoclonal antibodies are produced using Hybridoma technology, which involves fusing short-lived antibody-producing B-cells with immortal myeloma (cancer) cells to create a “hybrid” cell line.
Why other options are incorrect:
Why other options are incorrect:
- • Biotechnology: This is a broad field of science that includes hybridoma technology, but it is not the specific process name itself.
- • Fermentation Technology: This is used primarily for the mass production of microorganisms, antibiotics, or alcohols, rather than the generation of specific monoclonal antibodies.
- • None of these: Since Hybridoma technology is the established method, this option is incorrect.
First line of body defence is?
- a) Antibody molecules
- b) Unbroken skin
- c) Antigen molecules
- d) Phagocytic cells
Explanation:
The unbroken skin (along with mucous membranes) acts as the first line of defense. It provides a physical and chemical barrier that prevents the entry of pathogens into the body.
Why other options are incorrect:
Why other options are incorrect:
- • Antibody molecules: These are part of the third line of defense (adaptive immunity), produced specifically to target recognized pathogens.
- • Antigen molecules: These are not defenses; they are foreign substances (usually on the surface of pathogens) that trigger an immune response.
- • Phagocytic cells: These (like macrophages) make up the second line of defense, which attacks pathogens once they have already breached the skin.
What is the strength of the bond between antigen and antibody?
- a) Affinity
- b) Avidity
- c) Covalent
- d) None of these
Explanation:
Affinity is the measure of the binding strength between a single antigenic determinant (epitope) and a single combining site on an antibody.
Why other options are incorrect:
Why other options are incorrect:
- • Avidity: This refers to the overall strength of binding between a multivalent antibody and an antigen (the sum of all affinities).
- • Covalent: Antigen-antibody interactions are non-covalent (they rely on weak forces like hydrogen bonds, ionic bonds, and Van der Waals forces).
- • None of these: Since “Affinity” is the scientifically correct term for the strength of a single bond, this option is incorrect.
Syphilis is caused by?
- a) Staphylococcus aureus
- b) Yersinia pestis
- c) Treponema pallidum
- d) Streptococcus syphilitis
Explanation:
Syphilis is a sexually transmitted infection (STI) caused by the bacterium Treponema pallidum, which is a spiral-shaped bacterium known as a spirochete.
Why other options are incorrect:
Why other options are incorrect:
- • Staphylococcus aureus: This bacterium commonly causes skin infections, respiratory infections, and food poisoning.
- • Yersinia pestis: This is the bacterium responsible for the Bubonic Plague.
- • Streptococcus syphilitis: This is a fictional name; while Streptococcus species cause many diseases (like strep throat), they do not cause syphilis.
Negri bodies produced by rabies virus show characteristic _ inner granules?
- a) Basophilic
- b) Eosinophilic
- c) Neutrophilic
- d) Acidophilic
Explanation:
Negri bodies are cytoplasmic inclusion bodies found in neurons infected with the rabies virus. While the body itself is eosinophilic, it contains characteristic basophilic (blue-staining) inner granules that help in definitive diagnosis.
Why other options are incorrect:
Why other options are incorrect:
- • Eosinophilic: This describes the main mass of the Negri body, but the question specifically asks for the nature of the inner granules.
- • Neutrophilic: This refers to neutral staining; Negri body components show distinct affinity for acidic or basic dyes.
- • Acidophilic: This is a synonym for eosinophilic; it describes the surrounding matrix of the inclusion body rather than the internal granules.
The widely used yeast for the production of single cell protein is?
- a) Saccharomyces cerevisiae
- b) Rhizopus
- c) Candida utilis
- d) All of the above
Explanation:
Candida utilis (also known as Torula yeast) is the most widely used yeast for Single Cell Protein (SCP) production. It is highly valued because it can utilize a wide variety of carbon sources, including industrial waste like wood sugars and sulfite liquor from paper mills.
Why other options are incorrect:
Why other options are incorrect:
- • Saccharomyces cerevisiae: While used in baking and brewing, and sometimes as SCP, it is more limited in the types of sugars it can ferment compared to Candida utilis.
- • Rhizopus: This is a genus of filamentous fungi (molds), not a yeast.
- • All of the above: Since Rhizopus is not a yeast and Candida utilis is the primary choice for SCP, this option is incorrect.
Analysis of protein antigen is by?
- a) Southern blot
- b) Northern blot
- c) Western blot
- d) None of these
Explanation:
Western blot (also known as protein immunoblot) is the standard laboratory method used to detect and analyze specific protein antigens in a complex mixture using antibodies.
Why other options are incorrect:
Why other options are incorrect:
- • Southern blot: This technique is used specifically for the detection of DNA sequences.
- • Northern blot: This technique is used specifically for the study of gene expression by detection of RNA.
- • None of these: Since Western blot is the correct analytical method for proteins, this option is incorrect.
Which of the following can provide naturally acquired passive immunity for the new born?
- a) IgA
- b) IgG
- c) IgE
- d) IgM
Explanation:
IgG is the only class of antibody that can cross the placenta from the mother to the fetus. This provides the newborn with “naturally acquired passive immunity” that protects them during the first few months of life.
Why other options are incorrect:
Why other options are incorrect:
- • IgA: While secretory IgA is provided to the newborn through breast milk/colostrum (also a form of natural passive immunity), IgG is the primary antibody transferred in utero for systemic protection.
- • IgE: This antibody is primarily involved in allergic reactions and defense against parasitic worms; it does not provide passive immunity to newborns.
- • IgM: These molecules are too large to cross the placental barrier. IgM is usually the first antibody the newborn’s own body produces in response to an infection.
AIDS disease is caused by a virus which belongs to?
- a) Retro virus group
- b) Rhabdo virus group
- c) Hepatitis virus group
- d) Adeno virus group
Explanation:
AIDS is caused by the Human Immunodeficiency Virus (HIV), which belongs to the Retrovirus group. These viruses are characterized by having an RNA genome and using the enzyme reverse transcriptase to convert their RNA into DNA once inside a host cell.
Why other options are incorrect:
Why other options are incorrect:
- • Rhabdo virus group: This group includes bullet-shaped viruses, such as the Rabies virus.
- • Hepatitis virus group: This is a diverse group of viruses (A, B, C, D, E) that specifically target the liver.
- • Adeno virus group: These are non-enveloped DNA viruses that typically cause respiratory infections, conjunctivitis, or gastroenteritis.
Complement based agglutination reaction is known as?
- a) Haem agglutination
- b) Complement fixation
- c) Conglutination
- d) Schultz Dale Phenomenon
Explanation:
Conglutination is a specific type of agglutination reaction that occurs when an antigen-antibody complex binds with complement and is then clumped together by a substance called ‘conglutinin’ (found in bovine serum).
Why other options are incorrect:
Why other options are incorrect:
- • Haem agglutination: This refers to the clumping of red blood cells, often caused by viruses or specific antibodies, but does not inherently require the complement system.
- • Complement fixation: This is a diagnostic test used to detect the depletion of complement in a system, rather than using complement as an agent to cause agglutination.
- • Schultz Dale Phenomenon: This is an in-vitro laboratory test used to demonstrate immediate hypersensitivity (anaphylaxis) using smooth muscle contraction.
Reverse transcriptase is an enzyme involved in the synthesis of?
- a) DNA
- b) Soluble RNA
- c) m-RNA from DNA
- d) Nucleotides
Explanation:
Reverse transcriptase is an enzyme that synthesizes complementary DNA (cDNA) from an RNA template. This process is the “reverse” of normal transcription.
Why other options are incorrect:
Why other options are incorrect:
- • Soluble RNA: This refers to tRNA, which is synthesized by RNA polymerase III, not reverse transcriptase.
- • m-RNA from DNA: This is the process of standard transcription, which is performed by the enzyme RNA polymerase.
- • Nucleotides: These are the chemical building blocks of nucleic acids; they are synthesized via complex metabolic pathways, not by a transcriptase enzyme.
The cellular immune response is mediated by?
- a) B cells
- b) T cells
- c) BT cells
- d) Endothelial cells
Explanation:
The cellular immune response (or cell-mediated immunity) is primarily mediated by T cells (T lymphocytes). These cells do not produce antibodies but rather destroy infected host cells directly or release cytokines to manage the immune response.
Why other options are incorrect:
Why other options are incorrect:
- • B cells: These are responsible for humoral immunity, which involves the production of antibodies.
- • BT cells: This is not a recognized single cell type; B cells and T cells are distinct lineages of lymphocytes.
- • Endothelial cells: These are the cells that line the blood vessels; while they play a role in inflammation, they do not mediate the adaptive cellular immune response.
The major immunoglobulin present in the human serum is?
- a) IgG
- b) IgA
- c) IgE
- d) IgM
Explanation:
IgG is the most abundant immunoglobulin in human serum, accounting for approximately 75% to 80% of the total circulating antibodies. It plays a critical role in long-term immunity and can cross the placenta.
Why other options are incorrect:
Why other options are incorrect:
- • IgA: While it is the second most common in serum, it is the predominant antibody found in external secretions like saliva, tears, and breast milk.
- • IgE: This is found in the lowest concentration in serum and is primarily involved in allergic reactions and parasitic infections.
- • IgM: This is the largest immunoglobulin (pentamer) and is the first to be produced during a primary immune response, but its serum concentration is much lower than IgG.
Reagenic type antibody is?
- a) IgG
- b) IgA
- c) IgM
- d) IgE
Explanation:
IgE is referred to as the reagenic antibody (or reagin). It has a high affinity for mast cells and basophils and is the primary mediator of Type I hypersensitivity (allergic) reactions.
Why other options are incorrect:
Why other options are incorrect:
- • IgG: This is the most abundant antibody in serum and provides long-term immunity, but is not termed “reagenic.”
- • IgA: This is the “secretory antibody” found in mucus, saliva, and tears to protect body surfaces.
- • IgM: This is the “early response antibody,” being the first to appear after initial exposure to an antigen.
The reaction of soluble antigen with antibody is known by?
- a) Precipitation
- b) Flocculation
- c) Agglutination
- d) Complement fixation
Explanation:
A Precipitation reaction occurs when a soluble antigen reacts with its specific antibody in the presence of an electrolyte (like NaCl) at a suitable temperature and pH to form an insoluble visible complex.
Why other options are incorrect:
Why other options are incorrect:
- • Flocculation: This is actually a type of precipitation where the precipitate remains suspended as flakes rather than settling at the bottom, but “Precipitation” is the standard general term.
- • Agglutination: This term is used when the antigen is particulate (insoluble), such as whole bacteria or red blood cells, which clump together.
- • Complement fixation: This is a complex immunological medical test used to detect the presence of either specific antibodies or specific antigens in a patient’s serum.
Interferon is composed of?
- a) Lipids
- b) Lipoprotein
- c) Glycoprotein
- d) Nucleic acid
Explanation:
Interferons (IFNs) are a group of signaling proteins made and released by host cells in response to the presence of several viruses. Chemically, they are glycoproteins, which means they consist of polypeptide chains conjugated with carbohydrates.
Why other options are incorrect:
Why other options are incorrect:
- • Lipids: These are fats and oils; interferons are protein-based signaling molecules.
- • Lipoprotein: While these contain proteins, they are primarily associated with the transport of fats in the blood (like LDL or HDL), which is not the structure of interferons.
- • Nucleic acid: These are the building blocks of DNA and RNA. Interferons are proteins produced from genetic templates, but they are not nucleic acids themselves.
Agglutination reaction is strongest with the immunoglobulin?
- a) IgM
- b) IgG
- c) IgA
- d) IgD
Explanation:
IgM is the most efficient immunoglobulin for agglutination. Because it exists as a pentamer (5 units) with 10 binding sites, it can easily cross-link multiple particulate antigens (like bacteria or red blood cells) simultaneously.
Why other options are incorrect:
Why other options are incorrect:
- • IgG: It is a monomer with only 2 binding sites. While it can cause agglutination, it is much less efficient than IgM.
- • IgA: In serum, it is usually a monomer; in secretions, it is a dimer. Neither form has as many binding sites as the IgM pentamer.
- • IgD: This is primarily found on the surface of B-cells as a receptor and is present in very low concentrations in the blood, playing no significant role in agglutination.
The use of monoclonal antibodies is?
- a) Immunotherapy
- b) Gene therapy
- c) Blood transfusion
- d) Organ transfusion
Explanation:
Immunotherapy utilizes monoclonal antibodies (mAbs) to treat diseases like cancer, autoimmune disorders, and infections. These antibodies are designed to bind specifically to target cells or proteins to stimulate the immune system or block harmful signals.
Why other options are incorrect:
Why other options are incorrect:
- • Gene therapy: This involves modifying or replacing faulty genes within a patient’s cells to treat disease, rather than using external antibodies.
- • Blood transfusion: This is the process of transferring whole blood or specific blood components (like RBCs or platelets) from a donor to a recipient.
- • Organ transfusion: (Commonly called Organ Transplantation) This is the surgical procedure of moving an organ from one body to another.
Hybridoma technique is used for?
- a) Monoclonal antibodies
- b) Polyclonal antibodies
- c) Both Monoclonal and Polyclonal
- d) None of these
Explanation:
The Hybridoma technique is a specialized method used to produce monoclonal antibodies. It involves fusing a short-lived, antibody-producing B lymphocyte with an “immortal” myeloma (cancer) cell to create a hybrid cell (hybridoma) that can produce a single type of antibody indefinitely.
Why other options are incorrect:
Why other options are incorrect:
- • Polyclonal antibodies: These are produced by collecting serum from an immunized animal. This serum contains a mixture of antibodies from many different B-cell clones, so hybridoma technology is not required.
- • Both: Hybridoma technology is specifically designed for cloning a single cell line, making it exclusive to monoclonal antibody production.
- • None of these: Since the production of monoclonal antibodies is the primary use of this technique, this option is incorrect.
Test used for AIDS is?
- a) Widal test
- b) ELISA
- c) Agglutination
- d) CFT
Explanation:
ELISA (Enzyme-Linked Immunosorbent Assay) is the primary screening test used to detect HIV antibodies in the blood. If an ELISA test is positive, a confirmatory test (like the Western Blot) is usually performed.
Why other options are incorrect:
Why other options are incorrect:
- • Widal test: This is a serological test used specifically for the diagnosis of Typhoid fever.
- • Agglutination: This is a general immunological reaction (clumping) used in many different tests, but it is not the specific name of the diagnostic test for AIDS.
- • CFT: Complement Fixation Test (CFT) is an older immunological medical test used to detect the presence of specific antibodies, but it is not the standard procedure for HIV/AIDS screening.
Antibody having high valency is?
- a) IgG
- b) IgA
- c) IgD
- d) IgM
Explanation:
IgM has the highest valency of all immunoglobulins. Because it exists as a pentamer (five antibody units joined together), it has a theoretical valency of 10, meaning it can bind up to 10 antigens simultaneously.
Why other options are incorrect:
Why other options are incorrect:
- • IgG: This is a monomer and has a valency of 2.
- • IgA: In serum, it is a monomer (valency 2), and in secretions, it is a dimer (valency 4). This is still lower than IgM.
- • IgD: Like IgG, it is a monomer and has a valency of 2.
Intensity of attraction between antigen and antibody molecule is known as?
- a) Affinity
- b) Avidity
- c) Reaction
- d) None of these
Explanation:
Affinity refers to the thermodynamic expression of the intensity or strength of the attraction between a single antigenic determinant (epitope) and a single antibody combining site (paratope).
Why other options are incorrect:
Why other options are incorrect:
- • Avidity: This is the overall stability or total binding strength of an antibody with an antigen that has multiple binding sites.
- • Reaction: This is a general term describing the process of two substances interacting, but it does not measure the “intensity” of that interaction.
- • None of these: Since Affinity is the standard immunological term for this concept, this option is incorrect.
Active immunity is induced by?
- a) Infection
- b) Placental transfer of antibodies
- c) Injection of antibodies
- d) Injection of gamma-globulins
Explanation:
Active immunity is induced when the body’s own immune system is stimulated to produce antibodies and memory cells in response to a foreign antigen. A natural infection is a primary way this occurs (Natural Active Immunity).
Why other options are incorrect:
Why other options are incorrect:
- • Placental transfer of antibodies: This is a form of Passive Immunity (specifically Natural Passive) because the baby receives “pre-made” antibodies from the mother.
- • Injection of antibodies: This is Artificial Passive Immunity. The recipient’s immune system is not active; it is simply receiving external help.
- • Injection of gamma-globulins: Gamma-globulin is another term for antibodies. Like option C, this provides temporary Passive Immunity and does not stimulate the host to produce its own antibodies.
Pasteur developed the vaccines for?
- a) Anthrax
- b) Rabies
- c) Chicken cholera
- d) All of the above
Explanation:
Louis Pasteur was a pioneer in immunology who developed the principle of attenuation (weakening a pathogen). He successfully developed vaccines for several devastating diseases during his lifetime.
Why all options are correct:
Why all options are correct:
- • Anthrax: He performed a famous public demonstration of his anthrax vaccine on cattle and sheep at Pouilly-le-Fort in 1881.
- • Rabies: In 1885, he developed the first rabies vaccine and successfully saved the life of Joseph Meister, a young boy bitten by a rabid dog.
- • Chicken cholera: This was actually his first discovery regarding artificial immunity, found by accidentally using an old, weakened culture of the bacteria.
Delayed type of hypersensitivity is seen in?
- a) Penicillin allergy
- b) Contact dermatitis
- c) Arthus reaction
- d) Anaphylaxis
Explanation:
Delayed-type hypersensitivity (DTH), also known as Type IV hypersensitivity, is a cell-mediated immune response. Unlike other types, it does not involve antibodies but is mediated by T-lymphocytes. It typically takes 48 to 72 hours to appear after exposure to the antigen. Contact dermatitis (e.g., reaction to nickel, poison ivy, or cosmetics) is a classic example.
Why other options are incorrect:
Why other options are incorrect:
- • Penicillin allergy: Most commonly presents as a Type I (immediate) hypersensitivity reaction mediated by IgE antibodies.
- • Arthus reaction: This is a Type III hypersensitivity reaction involving the deposition of antigen-antibody immune complexes in local tissues.
- • Anaphylaxis: This is a severe, life-threatening Type I hypersensitivity reaction that occurs immediately after exposure to an allergen.
The following are used for the preservation of virus, except?
- a) Freezing (–20°C–70°C)
- b) Lyophilization
- c) Ether
- d) Formaldehyde
Explanation:
Ether is not used for the preservation of viruses. Instead, it is commonly used to test the sensitivity of enveloped viruses because it can disrupt the viral envelope and inactivate the virus.
Why other options are correct:
Why other options are correct:
- • Freezing (–20°C–70°C): A common method for long-term storage and preservation of viruses.
- • Lyophilization: Freeze-drying helps maintain viral viability for extended periods.
- • Formaldehyde: Used to preserve viral preparations and in the production of inactivated vaccines.
Antibody formation depends on?
- a) Age of the person
- b) Amount of antigen
- c) Well being of the person
- d) All of the above
Explanation:
Antibody formation is influenced by several factors, including the age of the individual, the amount and nature of the antigen, and the overall health and nutritional status of the person. Therefore, all of these factors affect the immune response.
Why other options are incomplete:
Why other options are incomplete:
- • Age of the person: Immune responses vary with age; infants and elderly individuals often have weaker responses.
- • Amount of antigen: The dose of antigen can influence the strength of antibody production.
- • Well being of the person: Good health and nutrition support effective antibody formation.
Local immunity is important in?
- a) Influenza
- b) Allergy
- c) Polio
- d) All of these
Explanation:
Local immunity (mucosal immunity) refers to the immune response that occurs at specific entry points of the body, such as the respiratory, gastrointestinal, and genitourinary tracts, primarily mediated by Secretory IgA.
Why all options are correct:
Why all options are correct:
- • Influenza: Being a respiratory virus, local immunity in the nasal and lung mucosa is the first line of defense to prevent viral entry.
- • Allergy: Allergic reactions are often localized to specific tissues (like the skin, eyes, or airway) where the allergen makes contact.
- • Polio: The poliovirus enters through the gut. Local intestinal immunity (induced by the oral polio vaccine) is crucial to prevent the virus from multiplying in the intestines.
- • Conclusion: Therefore, local immunity plays a critical role in managing and preventing all three conditions.
Role of magnesium in vaccine is?
- a) Adjuvant
- b) Stabilizer
- c) Conditioner
- d) All of these
Explanation:
Magnesium (specifically Magnesium Chloride, MgCl₂) is used as a stabilizer in vaccines, most notably in the Oral Polio Vaccine (OPV). It helps maintain the potency of the vaccine and protects it against heat inactivation.
Why other options are incorrect:
Why other options are incorrect:
- • Adjuvant: Adjuvants are substances (like Aluminum salts) added to enhance the body’s immune response to the antigen. Magnesium does not serve this primary function.
- • Conditioner: This is not a standard pharmacological term used for components in vaccine formulation.
- • All of these: Incorrect, as the specific scientific role of magnesium is to provide thermostability (stabilization).
Immunity is life long following?
- a) Diphtheria
- b) Tetanus
- c) Measles
- d) Yellow fever
Explanation:
Natural infection with measles usually produces strong, long-lasting, often lifelong immunity due to the development of immunological memory.
Why other options are incorrect:
Why other options are incorrect:
- • Diphtheria: Infection does not reliably produce lifelong immunity, and booster vaccinations may be required.
- • Tetanus: Natural infection does not confer lasting immunity because very little toxin is needed to cause disease.
- • Yellow fever: Vaccination provides long-term protection, but the classic example of lifelong natural immunity is measles.
To prepare vaccine for small pox, the material used by Edward Jenner is?
- a) Small pox material
- b) Chicken pox material
- c) Cow-pox material
- d) Measles material
Explanation:
Edward Jenner, known as the “Father of Immunology,” used material from Cow-pox lesions to create the first vaccine. He observed that milkmaids who had contracted cowpox were immune to smallpox.
Why other options are incorrect:
Why other options are incorrect:
- • Small pox material: Using smallpox material to induce immunity was called “variolation.” Jenner’s breakthrough was replacing this dangerous method with the safer cowpox virus.
- • Chicken pox material: Chickenpox is caused by the Varicella-zoster virus, which is genetically very different from smallpox and does not provide cross-immunity.
- • Measles material: Measles is a respiratory virus that has no historical or biological connection to the development of the smallpox vaccine.
During recombination, the strain that donates genetic material frequently with high rate?
- a) Hfr-Strain
- b) F+-Strain
- c) F-Strain
- d) both Hfr-Strain and F-Strain
Explanation:
The Hfr (High Frequency of Recombination) strain is a bacterium with a conjugative plasmid (like the F-factor) integrated into its genomic DNA. During conjugation, it attempts to transfer its entire chromosome to the recipient, leading to a much higher rate of genetic recombination than a standard F+ strain.
Why other options are incorrect:
Why other options are incorrect:
- • F+-Strain: While these are donors, they typically only transfer the F-plasmid itself, not the chromosomal DNA, so the recombination rate of the host’s genome is low.
- • F-Strain: This is the recipient strain (female). It lacks the fertility factor and therefore cannot donate genetic material.
- • both Hfr-Strain and F-Strain: This is incorrect because the F-strain is strictly a recipient and does not donate material.
The character acquired by the cell due to recombination is?
- a) Inheritable
- b) Suppressed
- c) Dominating
- d) Heritable
Explanation:
When a cell undergoes recombination, new genetic material is integrated into its genome. This change is heritable, meaning it is passed down from the parent cell to all subsequent generations (daughter cells) during division.
Why other options are incorrect:
Why other options are incorrect:
- • Inheritable: While “inheritable” and “heritable” are often used interchangeably, in biological terminology, “heritable” is the more standard term used to describe traits determined by genes that are capable of being passed to offspring.
- • Suppressed: Recombined genes are not necessarily suppressed; they are often expressed to provide the cell with new capabilities (like antibiotic resistance).
- • Dominating: A recombined trait isn’t always “dominating” in a Mendelian sense; it simply refers to the successful integration and expression of new DNA.
B-cells are produced from?
- a) Bone marrow
- b) Thymus
- c) Spleen
- d) None of these
Explanation:
In mammals, B-cells (B lymphocytes) are produced and undergo maturation in the Bone marrow. The “B” in B-cells originally referred to the Bursa of Fabricius in birds, but in humans, it conveniently stands for Bone marrow.
Why other options are incorrect:
Why other options are incorrect:
- • Thymus: This is the primary lymphoid organ where T-cells mature, not B-cells.
- • Spleen: The spleen is a secondary lymphoid organ where B-cells migrate to encounter antigens, but it is not the site of their initial production.
- • None of these: This is incorrect because Bone marrow is the definitive site of B-cell hematopoiesis.
Antibodies are produced from?
- a) T-cells
- b) β-cells
- c) NK cells
- d) Eosinophils
- e) B-cells
Explanation:
B-cells (B-lymphocytes) are responsible for the humoral immune response. When a B-cell encounters its specific antigen, it differentiates into a plasma cell, which acts as a factory to secrete large quantities of antibodies.
Why other options are incorrect:
Why other options are incorrect:
- • T-cells: These are involved in cell-mediated immunity (direct killing of infected cells or coordinating the immune response) but do not produce antibodies.
- • β-cells (Beta cells): These are cells found in the pancreas that produce insulin, not part of the immune system’s antibody production.
- • NK cells: Natural Killer cells are part of the innate immune system and destroy virally infected or tumor cells directly.
- • Eosinophils: These are white blood cells mainly involved in fighting multicellular parasites and certain allergic reactions.
Incomplete antigens are called?
- a) Immunogens
- b) Epitopes
- c) Haptens
- d) Paratope
Explanation:
Haptens are known as incomplete antigens. They are small molecules that are antigenic (can react with specific antibodies) but are not immunogenic on their own (cannot stimulate an immune response unless attached to a large carrier protein).
Why other options are incorrect:
Why other options are incorrect:
- • Immunogens: These are complete antigens that can independently initiate an immune response.
- • Epitopes: Also called antigenic determinants, these are the specific chemical groups on the surface of an antigen to which an antibody binds.
- • Paratope: This is the part of the antibody (not the antigen) that recognizes and binds to the epitope.
To be antigen, the chemical molecule (protein) needs?
- a) High molecular weight
- b) Chemical complexity
- c) Both High molecular weight and Chemical complexity
- d) None of these
Explanation:
For a substance to be immunogenic (a complete antigen), it must generally have a high molecular weight (typically above 10,000 Daltons) and a complex chemical structure to be recognized by the immune system.
Why other options are incorrect:
Why other options are incorrect:
- • High molecular weight: While size is important, a large molecule with a very simple, repetitive structure (like a simple plastic polymer) may still not be antigenic.
- • Chemical complexity: Complexity is required for the immune system to find specific “epitopes,” but if the molecule is too small (low molecular weight), it may act only as a hapten rather than a full antigen.
- • None of these: Incorrect, as both molecular weight and complexity are fundamental requirements for antigenicity.
The Part which filter lymph are?
- a) Lymph nodes
- b) Spleen
- c) Thymus
- d) Bone Marrow
Explanation:
Lymph nodes are small, bean-shaped structures that act as biological filters. As lymph fluid circulates through the body, it passes through these nodes where foreign particles, bacteria, and cancer cells are trapped and destroyed by immune cells.
Why other options are incorrect:
Why other options are incorrect:
- • Spleen: The spleen is responsible for filtering the blood, removing old red blood cells and pathogens from the circulatory system, not the lymphatic system.
- • Thymus: This is a primary lymphoid organ where T-lymphocytes (T-cells) mature, but it does not function as a filter for lymph.
- • Bone Marrow: This is the site of hematopoiesis (production of blood cells) and the maturation of B-cells, but it has no role in filtering lymph fluid.
The primary cells involved in immune response are?
- a) NK-cells
- b) K-cells
- c) Lymphocytes
- d) None of these
Explanation:
Lymphocytes are the fundamental cells of the immune system. This category includes B-cells (which produce antibodies), T-cells (which coordinate the immune response and kill infected cells), and Natural Killer (NK) cells.
Why other options are incorrect:
Why other options are incorrect:
- • NK-cells: While these are important, they are a specific subset of lymphocytes. The question asks for the primary category, making “Lymphocytes” the more complete answer.
- • K-cells: These usually refer to “Killer cells” or cells involved in Antibody-Dependent Cell-mediated Cytotoxicity (ADCC). Like NK-cells, they are specific types rather than the overarching primary group.
- • None of these: Incorrect, as lymphocytes are universally recognized as the primary cells of the immune response.
Plasma cells are the end cells of?
- a) T-cells
- b) β-cells
- c) Killer cells
- d) B-cells
Explanation:
Plasma cells are fully differentiated B-cells (B-lymphocytes). When a B-cell is activated by an antigen, it matures into a plasma cell, which functions as a factory to produce and secrete large quantities of antibodies.
Why other options are incorrect:
Why other options are incorrect:
- • T-cells: These cells are involved in cell-mediated immunity. They differentiate into Helper, Cytotoxic, or Memory T-cells, but never into antibody-secreting plasma cells.
- • β-cells: These are endocrine cells found in the pancreas (Islets of Langerhans) that produce insulin; they are part of the metabolic system, not the lymphatic “B-cell” lineage.
- • Killer cells: This term usually refers to Cytotoxic T-lymphocytes or Natural Killer (NK) cells, which destroy infected or cancerous cells directly rather than producing antibodies.
Basophils have receptors for antibodies?
- a) IgG
- b) IgA
- c) IgM
- d) IgE
Explanation:
Basophils (along with mast cells) possess high-affinity receptors (known as FcεRI) specifically for IgE antibodies. When an allergen binds to the IgE already attached to these receptors, it triggers the basophil to release histamine and other mediators, causing an allergic response.
Why other options are incorrect:
Why other options are incorrect:
- • IgG: This is the most abundant antibody in the blood used for general defense; while some cells have IgG receptors (FcγR), they are not the primary defining receptors for basophil activation in allergies.
- • IgA: Found primarily in secretions (tears, saliva, mucus) to protect mucosal surfaces, rather than triggering basophils.
- • IgM: The first antibody produced in an infection, acting as a powerful neutralizer and complement activator, but it does not typically bind to basophils to mediate allergic reactions.
Because of denaturation, antigens become functionless, these are called?
- a) Cross-reactive antigens
- b) Epitopes
- c) Hidden epitopes
- d) Forssman antigens
Explanation:
Many antigens depend on their three-dimensional shape (conformation) to be recognized by the immune system. When a protein is denatured (by heat or chemicals), it unfolds. Epitopes that were previously on the surface may be destroyed, while others that were buried inside the molecule—called Hidden epitopes—may be revealed or rendered non-functional in the context of the original native protein.
Why other options are incorrect:
Why other options are incorrect:
- • Cross-reactive antigens: These are antigens that share similar epitopes, causing an antibody produced against one to react with the other. Denaturation is not the defining factor here.
- • Epitopes: This is a general term for the specific part of an antigen to which an antibody binds. It doesn’t specifically describe the “functionless” state caused by denaturation.
- • Forssman antigens: These are a specific type of heterophile antigen found in various species (like sheep RBCs) but not in humans; they are defined by their biological origin, not by denaturation.
Capacity of antigen to breakdown into small fragments each with a single epitopic region is known as?
- a) Solubility
- b) Foreignness
- c) Denaturation
- d) None of these
Explanation:
Denaturation is the process by which an antigen’s complex structure is altered or broken down into smaller fragments, often exposing or separating individual epitopic regions. This property can affect the antigenicity of the molecule.
Why other options are incorrect:
Why other options are incorrect:
- • Solubility: Refers to the ability of a substance to dissolve in a solvent and is unrelated to epitope fragmentation.
- • Foreignness: Describes how different an antigen is from the host’s own molecules, influencing immunogenicity.
- • None of these: Incorrect because denaturation best matches the described property.
Antigenic specificity is due to?
- a) Chemical complexity
- b) Solubility
- c) Steric configuration
- d) All of these
Explanation:
Antigenic specificity is mainly determined by the steric configuration (three-dimensional shape) of the antigenic determinants (epitopes), which allows precise recognition by antibodies or T-cell receptors.
Why other options are incorrect:
Why other options are incorrect:
- • Chemical complexity: Contributes to immunogenicity but not direct specificity.
- • Solubility: Has no role in determining antigen-antibody recognition specificity.
- • All of these: Incorrect because only steric configuration directly governs specificity.
Antibodies are?
- a) Proteins
- b) Glycoproteins
- c) Phospholipids
- d) None of these
Explanation:
Antibodies (Immunoglobulins) are chemically glycoproteins. They consist primarily of polypeptide chains (proteins) with carbohydrate chains (sugars) attached to the heavy chains.
Why other options are incorrect:
Why other options are incorrect:
- • Proteins: While antibodies are made of proteins, “Glycoproteins” is a more precise biochemical description because of the essential carbohydrate component.
- • Phospholipids: These are the main components of cell membranes, consisting of fatty acids and a phosphate group. They do not function as antibodies.
- • None of these: Incorrect, as glycoproteins accurately describes the molecular nature of all immunoglobulins.
General purpose antibody is?
- a) IgA
- b) IgG
- c) IgM
- d) IgD
Explanation:
IgG is often referred to as the “general purpose” antibody because it is the most abundant class (constituting about 75-80% of total serum antibodies). It is versatile, capable of crossing the placenta, opsonizing pathogens, and neutralizing toxins.
Why other options are incorrect:
Why other options are incorrect:
- • IgA: This is the primary “secretory” antibody, specialized for protecting mucosal surfaces like the respiratory and digestive tracts.
- • IgM: This is the “early response” antibody. It is the first to be produced during an infection but is later replaced by IgG for long-term protection.
- • IgD: This antibody is found primarily on the surface of B-cells acting as an antigen receptor; its function in the general circulation is very limited.
Antibody present in colostrums is?
- a) IgG
- b) IgA
- c) IgM
- d) IgE
Explanation:
IgA (specifically Secretory IgA) is the predominant antibody found in colostrum (the first milk produced after birth) and mature breast milk. It provides essential passive immunity to the newborn by protecting the infant’s mucosal surfaces, especially the digestive tract, from pathogens.
Why other options are incorrect:
Why other options are incorrect:
- • IgG: In humans, IgG is primarily transferred from mother to fetus through the placenta during pregnancy, rather than being the main component of colostrum.
- • IgM: While small amounts of IgM can be found in colostrum, it is not the primary or most significant immunoglobulin provided through breastfeeding.
- • IgE: This antibody is associated with allergic reactions and parasitic infections; it is found in only trace amounts in breast milk and does not provide nutritional immunity to the infant.
Which antibody is called millionaire molecule?
- a) IgA
- b) IgM
- c) IgG
- d) IgD
Explanation:
IgM is known as the “millionaire molecule” because of its massive molecular weight. It has a pentameric structure (consisting of 5 basic units joined together), resulting in a molecular weight of approximately 900,000 to 1,000,000 Daltons.
Why other options are incorrect:
Why other options are incorrect:
- • IgG: This is the smallest and most common antibody, with a molecular weight of only about 150,000 Daltons.
- • IgA: While it can form dimers, its weight (approx. 160,000–320,000 Daltons) is far lower than that of IgM.
- • IgD: This monomeric antibody has a molecular weight of around 180,000 Daltons, much smaller than the “millionaire” IgM.
IgE is discovered by?
- a) Ishizaka
- b) Porter
- c) Richet
- d) None of these
Explanation:
Kimishige and Teruko Ishizaka discovered the IgE antibody in 1966. They identified it as a new class of immunoglobulins that mediates allergic reactions (Type I hypersensitivity).
Why other options are incorrect:
Why other options are incorrect:
- • Porter: Rodney Porter (along with Gerald Edelman) won the Nobel Prize for determining the chemical structure of antibodies, but he did not discover the IgE class.
- • Richet: Charles Richet discovered anaphylaxis (for which he won a Nobel Prize), but the specific molecule (IgE) responsible for it was not identified until decades later by the Ishizakas.
- • None of these: Incorrect, as the Ishizakas are internationally recognized for this discovery.
Answer Key Summary
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