Chapter – 4A and 4B : Biology and Human Welfare | Chapter Solution Class 9

(c) Tiselius (1937)

Explanation:

Arne Tiselius was the first to name and characterize antibodies in 1937, using electrophoresis to analyze serum proteins, which led to the discovery of gamma globulin as antibodies.

(b) 5 types

Explanation:

There are five major classes of antibodies: IgA, IgD, IgE, IgG, and IgM, each with a specific function in the immune response.

(b) Immunoglobulin

Explanation:

IgG stands for Immunoglobulin G. It is the most abundant antibody in the blood and provides long-term protection by neutralizing pathogens and activating other immune components.

(a) Specific immunity

Explanation:

Specific immunity (adaptive immunity) retains memory of previously encountered antigens, allowing for faster and stronger responses upon re-exposure.

(b) Passive

Explanation:

Passive immunity is conferred when antibodies (mostly IgG) are passed from the mother to the fetus through the placenta, providing temporary protection.

(c) Innate

Explanation:

Innate immunity is the natural defense system present from birth. It provides immediate, non-specific defense against pathogens.

(c) Plasma cells

Explanation:

When activated, B-cells differentiate into plasma cells that secrete antibodies to neutralize antigens.

(c) Plasma cells

Explanation:

When activated, B-cells differentiate into plasma cells that secrete antibodies to neutralize antigens.

(b) E. Jenner

Explanation:

Edward Jenner introduced the concept of vaccination and coined the term based on “vacca” (Latin for cow) after using cowpox virus to protect against smallpox.

Protein

Explanation: Antibodies are glycoproteins known as immunoglobulins, made up of polypeptide chains. They are produced by B-cells in response to antigens.

B-lymphocytes

Explanation: The humoral immune response is mediated by B-lymphocytes, which produce antibodies that circulate in body fluids (humors) to target antigens.

Edward Jenner

Explanation: Edward Jenner coined the term vaccine after using cowpox (from “vacca” meaning cow in Latin) to protect against smallpox, founding the concept of vaccination.

Tuberculosis

Explanation: BCG (Bacille Calmette-Guerin) vaccine is given to prevent tuberculosis (TB). It is administered soon after birth in many countries.

Clostridium tetani

Explanation: Tetanus is caused by the bacterium Clostridium tetani, which releases a neurotoxin leading to severe muscle spasms and stiffness.

True

Explanation: Rhizobium is a nitrogen-fixing bacterium that lives symbiotically in the root nodules of leguminous plants, helping to convert atmospheric nitrogen into a usable form.

True

Explanation: Penicillin was the first true antibiotic discovered by Alexander Fleming in 1928. It is derived from the fungus Penicillium notatum.

True

Explanation: Proper hand hygiene is essential to prevent the spread of pathogens, especially after using the bathroom, to reduce transmission of fecal-oral infections.

True

Explanation: Baculoviruses are a group of DNA viruses used in biological pest control because they infect and kill specific insect pests without harming humans or other animals.

Epitopes

Reason: IgA, IgD, IgG are classes of antibodies (immunoglobulins). Epitopes are parts of antigens, not antibodies. Hence, it does not belong.

Malaria

Reason: Dengue, Hepatitis-A, and AIDS are all viral diseases, whereas Malaria is caused by a protozoan parasite (Plasmodium), making it the odd one.

Louis Pasteur

Explanation: Louis Pasteur is known as the Father of Immunology due to his pioneering work on vaccines and microbial fermentation. He developed vaccines for diseases like rabies and anthrax, laying the foundation for modern immunology.

IgG is the most abundant class of antibody in human blood.

Explanation: IgG (Immunoglobulin G) provides long-term protection by neutralizing toxins and viruses and is the only antibody that crosses the placenta to provide immunity to the fetus.

To the variable region of an antibody or receptors on immune cells.

Explanation: An antigen binds to the antigen-binding site (variable region) of an antibody or to antigen receptors on the surface of B-cells or T-cells, initiating an immune response.

Pathogen

Explanation: A pathogen is a microorganism (bacteria, virus, fungus, or protozoan) that can cause disease in the host organism, such as Mycobacterium tuberculosis (TB) or HIV (AIDS).

Skin and mucous membranes

Explanation: Skin acts as the first line of defense by providing a physical barrier, while mucous membranes trap and help eliminate microbes from respiratory, digestive, and urogenital tracts.

T-lymphocytes (T-cells)

Explanation: T-cells identify and destroy infected cells, cancer cells, and coordinate the immune response. Cytotoxic T-cells (CD8⁺) are the main effectors in cellular immunity.

Active immunity

Explanation: Active immunity occurs when the body is exposed to an antigen (via infection or vaccination), and it produces its own antibodies and memory cells for future protection.

An antigen is any substance, usually a protein or polysaccharide, that is recognized as foreign by the immune system and triggers an immune response.

Example: The spike protein of the SARS-CoV-2 virus acts as an antigen.

An antibody is a specialized Y-shaped glycoprotein produced by B-lymphocytes in response to the presence of an antigen. It binds specifically to that antigen to neutralize or eliminate it from the body.

There are five classes of antibodies: IgA, IgD, IgE, IgG, and IgM.

Immunity is the natural or acquired ability of the body to resist or fight against disease-causing organisms or harmful substances. It prevents infection and maintains health.

Acquired immunity is classified into two types:

1. Active immunity – Developed by the body after infection or vaccination.
2. Passive immunity – Gained through the transfer of ready-made antibodies, such as from mother to child.

B-cells, or B-lymphocytes, are a type of white blood cell that mature in the bone marrow. They are responsible for producing antibodies and are involved in humoral immunity.

Vaccination is the method of introducing a weakened or inactivated form of a pathogen or its antigen into the body to stimulate the immune system and provide protection against specific diseases.

1. Antigen: An antigen is a substance which induces the production of antibodies. It may be a pathogen, toxin, foreign protein, or part of a microorganism.
2. Antibody: An antibody is a protein produced by B-lymphocytes in response to a specific antigen. It binds to the antigen and neutralizes or destroys it.
3. Immunology: Immunology is the branch of science that deals with the study of the immune system, including the body’s defense mechanisms against pathogens and how immunity is developed.

Antibodies are classified into five major types based on their structure and function:

1. IgA – Found in body secretions like saliva, tears, and milk. It exists as a dimer.
2. IgD – Present on B-cell surfaces; involved in activation. It is a monomer.
3. IgE – Involved in allergic reactions and defense against parasites. It is a monomer.
4. IgG – The most abundant antibody in blood. Provides long-term immunity. It is a monomer.
5. IgM – First antibody produced during primary response. It exists as a pentamer.

All antibodies have a Y-shaped structure made up of two heavy chains and two light chains, connected by disulfide bonds. The tips of the “Y” form the antigen-binding sites.

Immunity is the body’s ability to recognize, destroy, and eliminate pathogens or foreign substances. It is of two types:

1. Innate immunity – Inborn and non-specific.
2. Acquired immunity – Developed after birth; specific to antigens.

Importance of immunity:

1. Defense Against Pathogens: Immunity helps the body recognize and fight off harmful microorganisms like bacteria, viruses, and fungi.
2. Prevention of Illness: A strong immune system reduces the risk of getting sick and helps us recover faster when we do fall ill.
3. Long-term Protection: After an infection or vaccination, the immune system can remember pathogens, providing long-lasting protection against future infections.
4. Maintaining Overall Health: A healthy immune system supports other bodily functions, ensuring that we stay well and can perform daily activities effectively.

Immunity is the ability of an organism to resist infection or disease by identifying and destroying harmful pathogens.

Classification:

(i) Innate Immunity – Present from birth and non-specific.

Example: Skin, phagocytes.

(ii) Acquired Immunity – Developed during life and specific to pathogens.

It is further divided into:

• Active immunity – Developed through infection or vaccine. Example: Immunity after chickenpox.
• Passive immunity – Antibodies received from another source. Example: Maternal antibodies via placenta.

Acquired Immunity Classification:

1. Active Immunity – This occurs when the body produces its own antibodies in response to an infection or vaccination. Example: Vaccination or natural infection.
2. Passive Immunity – Provided by antibodies transferred from another individual. Example: Antibodies from mother to fetus or through antiserum.

Humoral Immunity:

Humoral immunity is an acquired immune response involving B-lymphocytes that defend against pathogens in body fluids. When a foreign antigen enters, specific B-cells recognize it and are activated by helper T-cells. Activated B-cells multiply and form plasma cells (which produce antibodies) and memory B-cells. The antibodies neutralize pathogens by various mechanisms like agglutination, opsonization, and complement activation. Memory cells ensure a quicker response during future infections. This immunity is key to vaccination-based protection.

Cell-mediated immunity is a important part of the immune system that primarily involves T cells, a type of white blood cell. Unlike antibody-mediated immunity, which relies on antibodies produced by B cells, cell-mediated immunity focuses on directly attacking infected cells or cancer cells.

Here’s a brief overview of how it works:

1. T Cell Activation: When a pathogen (like a virus or bacteria) enters the body, it is processed by antigen-presenting cells (APCs) like dendritic cells. These APCs display pieces of the pathogen (antigens) on their surface.
2. Recognition: T cells recognize these antigens through their specific receptors. This recognition activates the T cells.
3. Types of T Cells:
   (a) Helper T Cells (CD4+ T cells): These cells help coordinate the immune response by releasing signals (cytokines) that stimulate other immune cells.
   (b) Cytotoxic T Cells (CD8+ T cells): These directly attack and kill infected or cancerous cells by releasing toxic substances.
4. Memory T Cells: After the immune response, some T cells become memory T cells. These cells remain in the body long-term and can respond more quickly if the same pathogen invades again in the future.

Vaccine: A vaccine is a preparation containing weakened or inactivated pathogens or their components that stimulate the immune system to produce antibodies.

Vaccination: Vaccination is the method of introducing a weakened or inactivated form of a pathogen or its antigen into the body to stimulate the immune system and provide protection against specific diseases.

Method of Vaccination

1. Inoculation through skin – as in pox vaccine
2. Intra-muscular injection – as in Diphtheria, Measles, Typhoid
3. Through swallowing – as in Polio vaccine

Vaccination helps develop active acquired immunity and prevents many infectious diseases.