NIOS Class 12 Biology Chapter 31 Immunobiology: an Introduction

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NIOS Class 12 Biology Chapter 31 Immunobiology: an Introduction

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Immunobiology: an Introduction

Chapter: 31

MODULE – V: EMERGING AREAS IN BIOLOGY

NIOS TEXTBOOK QUESTIONS ANSWERS

INTEXT QUESTIONS 31.1

1. Who is considered as father of immunobiology?

Ans:  Edward J enter.

2. What are the three main functions of immunological defence?

Ans: Immunological defence serves three functions. They are:

(a) The defence against the micro-organisms.

(b) Surveillance that is recognition and destruction of the mutant cells.

(c) Homeostasis that is “the removal of damaged (non functional) cells to maintain normal state of our body”.

3. Define immunology. 

Ans: The study of organisation and function of immune system is called “immunology.”

INTEXT QUESTIONS 31.2

1. Name the two categories of immune cells.

Ans: The two categories of immune cells are:

(a) Central or primary lymphoid organs.

(b) Peripheral or secondary lymphoid organs.

2. Name the organ found in birds where B-cells are produced. 

Ans: Bursa of Fabricius.

3. Write the two main functions of B-cells.

Ans: (a) They initiate antibody mediated immune response.

(b) They transform plasma cells that produce the antibodies.

4. Name the cells responsible for synthesis of antibodies.

Ans: Plasma cells are responsible for synthesis of antibodies.

5. What is the function of T-helper cells?

Ans: These promote response of B-cells that results into antibody production or they activate

other T-cells.

INTEXT QUESTIONS 31.3

1. Name the part of antigen which makes contact with antibody.

Ans: Epitope.

2. How many types of immunoglobulins are known? (Give only the number).

Ans: Five types.

3. Name the immunoglobulin found in highest concentration.

Ans: IgG is found in highest concentration.

4. Which type of immune response is responsible for the killing of cancer cells?

Ans: Cell Mediated Immune Response (CMI).

INTEXT QUESTIONS 31.4

1. Mention two physical barriers of the body.

Ans: (i) Skin on our body prevents entry of microbes.

(ii) Mucous coating of epithelium lining respiratory system traps microbes.

2. Macrophages are found in large numbers in the following organs:

Ans: (i) Thymus.

(ii) Spleen.

(iii) Tonsils.

(iv) Bone marrow.

(v) MALT.

3. Give two examples of each of the following:

(i) Killed organism vaccine.

Ans: Typhoid, cholera.

(ii) Live attenuated organism vaccine.

Ans: Polio and BCG.

(iii) Toxoid vaccine.

Ans: Tetanus and Diphtheria.

TERMINAL EXERCISES

1. Define the term immunity.

Ans: The immunity is defined as “capacity of body to recognize materials as foreign to itself and to neutralise, remove or metabolise them with or without injury to its own tissues”.

2. What are the main defence mechanisms operating in our body?

Ans: There are four defence mechanisms in our body:

(i) immunity to defend body against infections.

(ii) metabolic defence to metabolise as well as to detoxify foreign chemical substances.

(iv) stoppage of bleeding to check blood loss. and 

(iv) the resistance to the stress by releasing hormones mainly.

3. ‘Immune system is a complex network of cells, tissues and soluble factors’. Justify this statement.

Ans: Immune system: It is a network of cells, tissues and soluble factors that work in coordination. The cells of immune system are lymphoid cells and the macrophages. B-cells develop in bone marrow and T-cells in thymus gland. T-cells induce B cells to produce antibody. T-cells mediate regulatory and effector function. Antibodies are of five types. 

4. Describe the process of antibody production.

Ans: B-cells/B-lymphocytes transform into the plasma cells and these secrete antibodies. The plasma cells produce thousands of antibody molecules per second before they die within a day or whatsoever; some of the B-cells progeny do not differentiate into plasma cells but they become memory cells that produce antibodies when antigen reappears again. The capacity to produce antigen specific antibody is acquired by B cell during its development with prior exposure to an antigen.

Fig. 31.5. Differentiation and Antibody Production

5. List main functions of T-cells.

Ans: Main functions of T-cells are:

(a) They regulate immune response.

(b) Induce B-cells to produce antibody. and 

(c) They mediate CMI response.

6. Draw a schematic diagram of the structure of antibody.

Ans: Diagram of an antibody molecule: See (See Fig.

Fig. 31.6. Structure of an antibody molecule.

7. What are the main physical barriers of the body?

Ans: Main Physical barriers of Body: They include skin on body prevents entry of microbes in body. Body secretions ward off pathogens. HCI in stomach kills germs in food. Secretion from eye kills bacteria.

The Ten (1-10) natural physical barriers in body are shown in figure:

(a) Respiratory System	(b) Digestive or Alimentary System	(c) Skin

“First Line of Defence”

Fig. 31.7. Natural Physical Barriers to Infections.

8. Describe important features of phagocytic cells.

Ans: Important features of phagocytic cells:

(i) They possess digestive enzymes which break the engulfed materials.

(ii) are actively phagocytic cells.

(iii) form an important link between innate and acquired immunity.

(iv) these pass on the antigens or their products to lymphoid cells for the processing.

9. Give one main difference between passively acquired immunity and actively acquired immunity.

Ans: Difference between Actively acquired and Passively acquired Immunity:

Actively acquired Immunity	Passively acquired Immunity
1. When antibodies are produced by B-cells of our body in response to an antigen or infection; it is known as actively acquired immunity e.g., vaccination.	When antibodies produced in certain other vertebrate in response to deliberate infec-tion are injected into our body through serum or blood stream; it is known as passi-vely acquired immunity.
2. As the memory cells are stored in spleen and lymph nodes; they produce antibodies during second attack of disease, it lasts longer.	As no such storage is possi-ble and antibodies have to be taken a second time, it provides immunity only for a short period.

10. Define the process of attenuation.

Ans: Attenuation:

(i) It mimics natural behaviour of organism but does not cause disease/disorder.

(ii) The sustained antigen supply is provided by the organism which multiply/ reproduces actively.

(iii) Live weakened vaccines are organisms for cure of BCG, Rubella and polio diseases.

11. Name two toxoid vaccines.

Ans: (i) Tetanus. and 

(ii) Diphtheria.

12. What do the following abbreviations mean?

(i) BCG. 

Ans: BCG = Bacille Calmette Guerin.

(ii) DPT.

Ans: DPT = Diphtheria Pertusis Tetanus.

(iii) MMR.

Ans: MMR = Measles Mumps Rubella.