Test: Common Diseases in Humans & Immunity - Grade 12 MCQ

• The antibody recognizes a small portion of the antigen called the antigenic determinant or epitope.
• Each antibody recognizes and binds to a specific antigen in a lock and key type model.
• The variable regions, which make up the two identical antigen-binding sites, are different in each specific type of antibody, giving these sites specific shapes that fit certain antigenic epitopes.
• The remainder of the molecule consists of light and heavy chain constant regions where these amino acid sequences vary little from antibody to antibody.

• Antigen-binding site:

  
  Hence the correct option is 'A'

Line in NCERT: "Each antibody molecule has four peptide chains, two small called light chains and two longer called heavy chains."

• The production of antibodies by plasma cells in response to an antigen is called active immunity.
• Active immunity refers to the immune response that occurs when the body is exposed to a pathogen or foreign substance and produces its own antibodies in response. This type of immunity can be obtained naturally, such as through infection, or artificially, through vaccination. 
• Innate immunity is the body's first line of defense against pathogens and is present from birth. 
• Acquired immunity refers to the immune response that develops over time in response to exposure to various pathogens and foreign substances.
• Passive immunity, on the other hand, occurs when pre-formed antibodies are transferred from one individual to another, such as through maternal antibodies passed from mother to baby during breastfeeding.

Hence the correct option is 'D'

Line in NCERT: "When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host body. This type of immunity is called active immunity."

• Antibodies are produced by specialized white blood cells called B lymphocytes (or B cells). When an antigen binds to the B-cell surface, it stimulates the B cell to divide and mature into a group of identical cells called a clone.
• B cells, also known as B lymphocytes are a type of white blood cell of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system by secreting antibodies. B-cells bind to an antigen, receive help from a cognate helper T cell and differentiate into a plasma cell that secretes large amounts of antibodies.

Hence the correct option is 'B'
 

Line in NCERT: "The B-lymphocytes produce an army of proteins in response to pathogens into our blood to fight with them. These proteins are called antibodies."

The thymus reduces in size with age and becomes very small by the time puberty is attained.
This phenomenon is primarily due to changes in the thymus's function and tissue composition as an individual matures.

Hence the correct option is 'D'

Line in NCERT: "The thymus is quite large at the time of birth but keeps reducing in size with age and by the time puberty is attained it reduces to a very small size."

Chikungunya virus is most often spread to people by Aedes aegypti and Aedes albopictus mosquitoes. These are the same mosquitoes that transmit dengue virus.

• Mosquitoes become infected when they feed on a person already infected with the virus.
• Infected Mosquitoes can then spread the virus to other people through bites.

Hence the correct option is 'B'

Line in NCERT: "Such precautions have become more important especially in the light of recent widespread incidences of the vector-borne (Aedes mosquitoes) diseases like dengue and chikungunya in many parts of India."

• Snake antivenom is a medication made up of antibodies used to treat snake bites by venomous snakes. It is a type of antivenom.It contains antibodies.
• It is a biological product that typically consists of venom neutralizing antibodies derived from a host animal, such as a horse or sheep.
• The host animal is hyperimmunized to one or more snake venoms, a process which creates an immunological response that produces large numbers of neutralizing antibodies against various components (toxins) of the venom.
• The antibodies are then collected from the host animal, and further processed into snake antivenom for the treatment of envenomation.

Hence the correct option is 'D'

Line in NCERT: "Even in cases of snakebites, the injection which is given to the patients, contain preformed antibodies against the snake venom."

• Sporozoites enter the female Anopheles mosquito when they bite an infected person where these sporozoite fertilise and multiply in the stomach wall of the female Anopheles and stored in the salivary gland of mosquito till it is again transferred to the human body by a mosquito bite.
•  After entering the human body the sporozoites reach the liver cells, where they multiply. This is followed by their attack on red blood cells resulting in their rupture. The ruptured RBCs release a toxin called  hemozoin, which is responsible for high recurring fever, chills and shivering.
• Life cycle of malarial parasite in Female Anopheles mosquito:

Hence the correct option is 'C'

 

Line in NCERT: "The parasites multiply within them to form sporozoites that are stored in their salivary glands."

• Microorganisms that cause disease are collectively called pathogens.
• Pathogens cause disease either by disrupting the body's normal processes and/or stimulating the immune system to produce a defensive response, resulting in high fever, inflammation and other symptoms.

Hence the correct option is 'B'

Line in NCERT: "Such disease-causing organisms are called pathogens."

Infectious diseases are transmitted from one person to another by droplet infection, direct contact with infected persons, animal bite, contact with soil or by transplacental transmission.

Line in NCERT: "A healthy person acquires the infection by inhaling the droplets/aerosols released by an infected person or even by sharing glasses and utensils with an infected person."

Answer: Option D.

Solution: Malaria is caused by Plasmodium parasites, not a virus. The statement in R is true as the disease is indeed transmitted by the bite of infected Anopheles mosquitoes, making A false and R true.

Line in NCERT: "Plasmodium, a tiny protozoan is responsible for this disease."

​​​​​​​Lymphocytes are a unit of the immune system.

• Lymphocytes are one of several different types of white blood cells.
• Lymphocytes are of two types B cells and T cells.

1. When a macrophage engulfs organisms, B cells (humoral immunity) release antibodies which cause the destruction of bacteria.
2. The T cells (cell-mediated immunity) destroy the infectious organisms by killing the body cells that are affected.

Hence the correct option is 'C'

Line in NCERT: "The human immune system consists of lymphoid organs, tissues, cells and soluble molecules like antibodies."

Sickle-cell anaemia is a congenital disease. Congenital diseases are contracted before birth due to chromosomal abnormalities or gene mutations or defect in development. Goitre and Kwashiorkor are caused due to deficiency of an essential element while Rheumatoid Arthritis is an autoimmune disease.

• Acquired Immune Deficiency Syndrome or AIDS is a set of symptoms caused by the HIV virus.
• It is in fact, the most advanced stage of infection caused by HIV.
• This disease modifies and corrupts the immune system, making people susceptible to infections and diseases.

Hence the correct option is 'B'

Line in NCERT: "AIDS is caused by the Human Immuno deficiency Virus (HIV), a member of a group of viruses called retrovirus, which have an envelope enclosing the RNA genome."

The function of IgE antibody as mediators in allergic reactions of Type I is explained by their ability to interact both with antigen and with receptor molecules on the membrane of blood basophils and tissue mast cells. It is essential for type I hypersensitivity, which occurs as allergic asthma, rhinitis, and other allergic disorders. It also plays a key role in allergic reactions to anaphylactic medicines, bee stings, and antigen preparations used in immunotherapy tolerance.

Hence the correct option is 'B'  

Line in NCERT: "The antibodies produced to these are of IgE type."

Widal Test is used for diagnosis of Typhiod. Widal Test is used for diagnosis of Typhiod.

1. ESR is done to check out the concentration of Erythrocytes in blood.

2. PCR is done to amplify the amount of DNA molecules.

3. Widal test is a serological test for typhoid or enteric fever.

4. ELISA is done in AIDS.

Hence the correct option is 'C'

Line in NCERT: "Widal test: A classic case in medicine, that of Mary Mallon nicknamed Typhoid Mary, is worth mentioning here."