CUET UG Categorised PYQ Biology Unit 7

Primary lymphoid organs are sites where lymphocytes originate and mature. Bone marrow produces all blood cells including lymphocytes and serves as a primary lymphoid organ.

The thymus gradually reduces in size with age. The spleen is a large bean-shaped organ, reservoir of erythrocytes and blood filter.

The thymus is a primary lymphoid organ where T-lymphocytes mature. Tonsils, appendix and Peyer's patches function as secondary lymphoid organs.

NCERT describes MALT as lymphoid tissue associated with the mucosal lining of digestive, respiratory and urogenital tracts. Hence tonsils are not included in this description.

Peyer's patches are lymphoid tissues found in the small intestine and function as secondary lymphoid organs. Therefore statement C is incorrect.

Thymus is a primary lymphoid organ where T-lymphocytes mature and differentiate. Primary lymphoid organs are sites where lymphocytes develop and become immunocompetent.

Cancer treatment commonly involves surgery, radiotherapy and immunotherapy. Vaccination is mainly preventive and is not a standard treatment approach for existing cancers.

Entamoeba histolytica causes amoebiasis, Wuchereria bancrofti causes filariasis, Microsporum causes ringworm and Plasmodium falciparum causes malaria. Thus Option B provides the correct matching.

Each disease has a characteristic pathogen: Pneumonia → Haemophilus influenzae Typhoid → Salmonella typhi Malaria → Plasmodium falciparum Filariasis → Wuchereria bancrofti

Elephantiasis results from blockage of lymphatic vessels by Wuchereria bancrofti. It commonly causes inflammation and enlargement of lower limbs and gross deformities of genital organs.

Antibodies consist of two identical heavy chains and two identical light chains. These chains are connected through disulfide bonds, which stabilize the Y-shaped immunoglobulin molecule.

Antibodies are synthesized and secreted by plasma cells, which are activated B-lymphocytes. They play a major role in humoral immunity by recognizing and neutralizing antigens.

Antibodies consist of two heavy chains and two light chains. These chains are connected by disulphide bonds, which maintain the characteristic Y-shaped structure of the antibody molecule.

Helper T-lymphocytes stimulate B-lymphocytes to proliferate and differentiate into plasma cells. These plasma cells then produce antibodies. Therefore, T-lymphocytes indirectly help in antibody production.

Antibodies mediate humoral immunity because they are present in blood and lymph and act against pathogens present in body fluids.

The terminal regions of antibody arms contain antigen-binding sites. These variable regions specifically recognize and bind antigens, initiating an immune response.

Opioids such as morphine and heroin are derived from the latex of Papaver somniferum (opium poppy).

Innate immunity includes: Physical barriers → Skin and mucus. Physiological barriers → Stomach acid, tears and saliva. Therefore B, C and D are physiological barriers.

Retroviral replication proceeds as follows: Virus infects a normal cell. Viral RNA is converted into DNA by reverse transcriptase. Viral DNA integrates into host genome. Host machinery produces new viral RNA. Therefore the correct order is B → C → A → D.

ELISA (Enzyme Linked Immunosorbent Assay) relies on specific binding between an antigen and its corresponding antibody. This interaction allows detection of infections such as HIV.

The correct disease-pathogen matching is: Amoebiasis → Entamoeba histolytica (II) Filariasis → Wuchereria (I) Ringworm → Epidermophyton (IV) Pneumonia → Hemophilus influenzae (III) Therefore, the correct sequence is: (A) - (II), (B) - (I), (C) - (IV), (D) - (III)

The thymus is well developed during childhood and plays a major role in T-cell maturation. After puberty it gradually decreases in size, a process called involution.

Cancer treatment commonly includes surgery, radiation therapy and immunotherapy. Vaccination is generally preventive and physiotherapy is supportive rather than primary treatment.

Plasma cells are differentiated B-lymphocytes that synthesize and secrete large quantities of antibodies against specific antigens. They are the effector cells of humoral immunity.

An antibody molecule consists of four polypeptide chains: two identical heavy chains and two identical light chains. These chains are linked by disulfide bonds to form a Y-shaped structure. The variable regions bind antigens while the constant regions perform effector functions. Therefore, antibodies are composed of four peptide chains.

Malaria causes recurrent fever cycles due to rupture of infected RBCs. Filariasis causes inflammation and swelling of lymphatic vessels, especially lower limbs. Ringworm is a fungal infection producing scaly lesions on skin and nails. Amoebiasis causes blood and mucus in stools due to intestinal infection by Entamoeba histolytica.

Interferons are cytokines released by virus-infected cells. They induce antiviral defenses in nearby healthy cells and inhibit viral replication. Hence they are classified as cytokine barriers under innate immunity.

ELISA (Enzyme Linked Immunosorbent Assay) is based on the specific interaction between antigens and antibodies. The reaction is detected using enzyme-linked markers that produce a measurable color change. ELISA is widely used for diagnosis of infections such as HIV.

Nicotine is an alkaloid present in tobacco and acts primarily as a stimulant of the central nervous system. It stimulates the release of adrenaline, increasing blood pressure, heart rate, and alertness. Sedatives depress nervous activity, whereas analgesics relieve pain. Nicotine does neither of these functions effectively. Therefore, the statement that nicotine is a very effective sedative and painkiller is incorrect.