Biology: CUET Mock Test - 8 - Class 12 MCQ

An antibody is represented by H2L2 formula. Each antibody molecule has four peptide chains, two long chains called heavy or H chains and two short chains called light or L chains.

IgG and IgA antibodies are responsible for conferring Natural Passive Immunity to the foetus. IgG crosses the placenta during pregnancy and IgA antibodies are present in the yellowish fluid colostrum secreted by mother during the initial days of lactation.

IgM is the largest antibody amongst all because it has 10 paratopes or antigen binding sites. IgG antibody is the smallest amongst all.

Assimilation is not the function of an antibody. The functions of antibodies include Lysis, Neutralisation, Opsonisation, Precipitation and Agglutination.

IgG shows Opsonisation property. It is a property of Adherence where non-palatable antigen becomes palatable which helps in the endocytosis of pathogen by the macrophages.

IgM is the first antibody which is released during an infection site. IgM is also responsible for the initial activation of B-cells, macrophages and the complement system. It also makes up 7-10% of our total antibodies.

The given structure represents the structure of IgM. It is present in pentameric form and has 10 paratopes (Antigen Binding Sites).

Antigenic determinants are recognisable sites over antigens. Antigens are generally large molecules. The majority of them are made up of Proteins and Polysaccharides found on the cells walls of bacteria and other cells or the coat of viruses.

The above given structure is of an antibody molecule. Each antibody molecule has four peptide chains, two small called as light chains and two longer called heavy chains. Both chains are linked by disulphide bonds.

Humoral Immunity is also called as Antibody-mediated Immunity. Our immune system comprises of the antibodies present in the body humour-blood, lymph. Antibodies protect our body from pathogens that happen to enter blood and lymph.

Treponema pallidum is responsible for causes Syphilis. It is a bacterium. It is transmitted through sexual contact or exchange of blood or placenta to the foetus.

Hepatitis-B is caused by Hepatitis B virus (HBV). It is also a venereal disease or a sexually transmitted disease. The virus passes from one person to another by blood, semen or any other body fluids.

The site of infection relates to the type of sexual contact, occurring in mouth and throat after oral-genital contact, vagina and penis after genital contact or rectum after recto-genital contact.

The most common site of infection in female suffering from chlamydiasis is the cervix, resulting in cervicitis and production of thick mucus and pus discharge.

Urinogenital tract infection in males accompanied by yellow discharge, burning feeling on passing urine, fever and headache is ______
a) Gonorrhoea
b) Syphilis
c) Genital Herpes
d) Chancroid

Muscular Dystrophy is not a sexually transmitted disease. It is an autosomal dominant Mendelian disorder. Syphilis, Chancroid and Trichomoniasis are sexually transmitted diseases which are caused by Treponema pallidum, Haemophilus ducrei and Trichomonas vaginalis respectively.

In the first stage of syphilis, Chancre and rashes appear. Fever along with muscle and joints pain occur in the secondary stage. These symptoms also disappear. During the symptomless period which lasts for about 20 years, the bacteria may invade the body organs. When the signs of organ degeneration appear, the disease is said to be in a tertiary stage.

Gonorrhoea is a Sexually transmitted disease affecting both males and females’ genitals. If the bacteria causing Gonorrhoea are transmitted to the eyes of a new-born in the birth canal, blindness can result.

Candidiasis is a fungal infection due to Candida (a genera of yeast). When it affects the vagina, a white cottage cheese-like discharge occurs along with genital itching and burning.

Trichomoniasis is caused by Trichomonas vaginalis which is a flagellated protozoan. Trichomoniasis is an inflammation of the mucous membrane of the vagina in female and urethra in males.

In males, urethritis is the principal result of Chlamydia. Symptoms of Urethritis include a thick discharge, burning on urination, frequent and painful urination.

VDRL stands for Venereal Disease Research Laboratory. It is an antibody detection test used for diagnosing Syphilis. The VDRL test doesn’t look for the bacteria that cause syphilis. Instead, it checks for the antibodies our body makes in response to the antigens.

Ascaris shows sexual dimorphism. Female Ascaris is longer than male and has a straight posterior end while the males are shorter than females and have a curved posterior tail.

Ancylostoma is a roundworm which enters the body of a man through the skin of his foot if the person walks in soil barefoot. The roundworm causes Ancylostomiasis which is the infection of the small intestine.

Tapeworm infection amongst vegetarians occurs through the improperly washed raw vegetables and fruits. Sometimes these vegetables are infected with Taenia solium eggs. Therefore, it is very important to wash vegetables and fruits before consuming them.

The body of Tapeworm is divided into Scolex, Neck and Strobila. At the apex of scolex is a prominent mobile cone, the rostellum which is armed with 22 to 32 curved chitinous hooks, arranged in two rows. The scolex also bears four hemispherical, highly muscular sectorial organs, the true suckers. The suckers and hooks are the organs of attachment to the intestinal wall.

The common tapeworm infecting humans is Taenia saginata. It is commonly known as beef tapeworm where the intermediate host is cow, buffalo and sheep. Primary host is a man. Rostellum and Hooks are absent.

Helminthic diseases are generally spread through improper disposal of human stool containing eggs. These infected faeces contaminate soil, water, plants, food articles, etc. Dirty hands may spread the disease directly.

Filariasis is also known as Elephantiasis because of the excessive enlargement of legs. Filariasis is the infection of the lymphatic system which leads to the swelling of the infected organs like genital parts in male, limbs, mammary glands etc.

Stool Test can help to diagnose Roundworm Infection. The presence of eggs or a worm confirms the infection. Widal Test, Pap smear’s Test and Gravidex Test are used to detect Typhoid, Cervical Cancer and Pregnancy respectively.