A-antigen binding site,
B-variable region
C-constant region
D-light chain,
E-heavy chain (constant region),
F-disulphide bond

Following micro-organisms are associated with the manufacture of respective compounds:
(1) (a) Saccharomyces cerevisiae- Vinegar 
(b) Acetobacter sp.
(2) Saccharomyces cerevisiae- Alcohol
(3) Streptomyces aureofaciens- Tetracycline.
(4) Aspergillus niger-Citric Acid.

(i) Puffed up appearace of dough, which is used for making idli and dosa is due to release of CO₂ gas during fermentation by microbes.
(ii) Swiss cheese has large holes due to the production of CO₂.

(iii) Methanogens produce methane and CO_2.

Trichoderma polysporum is the source of cycloporin A.
Cylosporin A is used as an immuno-suppressive agent in organ-transplant patients.

(a) Contact inhibition is the property shown by normal cells,by the virtue of which contact with other cells inhibits their uncontrolled proliferation and growth.
(b) All normal cells have cellular oncogenes (c-onc) or proto-oncogenes;when activated under certain conditions,such genes could lead to oncogenic transformation of cells,i.e.they become cancerous.

When our body encounters an antigenic protein or a pathogen for the first time it produces a response which is of low intensity and our body retains memory of the first encounter.
The subsequent encounter with the same pathogen elicits a highly intensified response carried out with the help of two special types of lymphocytes present in our blood, i.e. B-lymphocytes and T-lymphocytes.
The B-lymphocytes produce an army of proteins in response to these pathogens into our blood to fight with them. These proteins are called antibodies. The T-cells themselves do not secrete antibodies, but help B-cells produce them.

(a) It is a cannabinoid.
(b) They are taken by:
(i) inhalation, and
(ii) oral ingestion.
(c) They affect the cardiovascular system.

Control of pests and plant diseases by using the biological methods is called biocontrol. It is a natural method of pest and pathogen control which is based natural predation. This involves the use of microorganisms like bacteria viruses, fungi, cyanobacteria and other natural predators and which bring about the control of pest and diseases e.g. Dragonfly prey upon mosquitoes, Baculorirusis attack insects and other arthropodes. They are species specific and do not cause harm to the non target beneficial organisms.

The name of gobar gas (or biogas) is methane.It is generated by the activity of methanogenic bacteria (i.e., methane producing anaerobic bacteria). Following are advantages of using methane as a source of energy:
(i) Methane is insoluble and therefore, separates very easily from the fermentor.
(ii) It can be very easily pressurized or liquefied for storage
(iii) It is readily combustible.

A sewage treatments plants is regarded as a giant microbial culture breading facility where the microbes are persuaded to work for our benefit.They metabolize the solid waste that passes through the treatment plant.The microbes oxidize the nutrients and during this process, they release energy in the form of heat and chemicals (phosphates, nitrates and sulphates) Gaseous by-product is also produced in the form of carbon dioxide.

Symptoms of Common Cold:
(i) Nasal congesion and discharge.
(ii) Sore throat and hoarseness.
(iii) Cough.
(iv) Headache.
It is caused by rhinoviruses.

(a) Amoebiasis is caused by Entamoeba histolytica.
(b) Symptoms:
(i) Constipation 
(ii) Abdominal cramps and pain.
(iii) Stool with excess mucus and blood clots.
Transmission 
Drinking water and food contaminated with the faeces of infected persons.
Houseflies act as mechanical carriers and transmit the parasite from faeces to food and water.

(i) People are careless, superstitious and unaware.
(ii) We can help in decreasing pollution of rivers by adopting following habits:
(a) By throwing litter or polybags in dustbin instead of rivers.
(b) By using environment friendly household products such as washing powder, household cleaning agents, etc.
(c) By planting more and more trees, which prevent fertilisers, pesticides and contaminated water from running in to nearby rivers.
(iii) Some advantages of saving rivers are:
(a) Constant supply of water and food to us.
(b) Huge supply of all natural fertilisers, which is good for growing crops.
(iv) Government has initiated Ganga Action Plan and Yamuna Action Plan to save these rivers from pollution.

Recombinant DNA vaccines are made up of a small circular DNA (plasmid) that has very tiny piece of pathogen DNA incorporated in it to produce one or two specific proteins of the pathogen.
This recombinant DNA is introduced into the bacteria or yeast cells, where it can use cell's machinery to produce polypetides of pathogen.
These are used as vaccines to trigger a range of immune responses. Vaccines produced by using this approach allow large scale production, e.g.
(i) Hepatits-B vaccines produced from yeast.
(ii) Bird flu DNA vaccine.
Advantages
(i) Recombinant DNA vaccines are advantageous over killed or attenuated vaccines since, they do not get virulent or mutated again as it is seen in case of attenuated vaccines.
(ii) Secondly these are highly pure, specific and elicit strong immune response.

(i)Aids is not contagious, i.r. it does not spread by shaking a hand, talking and use of common utensil. so, there is no need of fear to live with the AIDS patient.
(ii) Some preventive and safe steps to be suggested are:
(a)Taking HIV unaffected blood from a blood bank, ensuring the use of only disposable needles and syringes in all public and private hospitals and clinics.
(b)Free distribution of condoms in public.
(c)Advocating safe sex and promoting regular checkup for HIV in population.
(iii)AIDS is caused by Human Immunodeficiency Virus (HIV), a member of a group of viruses called retrovirus.This Virus attacks T-helper cells thus, Destroy the immune system.
The common symptoms of AIDS are a weakness, fever, weight loss, regular illness, etc.

(c) If Assertion is true but Reason is false.
Explantion:
Cell-mediated immunity (CMI) is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, antigen-specific cytotoxic Tlymphocytes, and the release of various cytokines in response to an antigen. The immune response to a transplanted organ consists of both cellular(lymphocyte mediated) and humoral (antibody mediated) mechanisms. Although other cell types are also involved, the T cells are central in the rejection of grafts.

Both A and R are true and R is not the correct explanation of A.

(a) If both A and R are true and R is the correct explanation of A

(d) : Azotobacter is a non -symbiotic nitrogen fixing bacteria that is it lives freely in the soil and perform nitrogen fixation. It is saprotrophic living on organic remains. Root nodules are formed by Rhizobium, a symbiotic nitrogen fixing bacteria.

(i) IgE antibody is released in allergic reactions.
(ii) Watery eyes, running nose, wheezing, sneezing, etc.
(iii) Adrenaline and steroids help to suppress and serotonin from the mast cells upon the entry of allergens in body. Thus, the allergic symptoms are either suppressed or reduced.
(iv) Autoimmune diseases are those in which the body begins to attack self-cells, e.g. rheumatoid arthritis, Addison's disease, etc.
(v) There are no permanent cures for autoimmune histamine diseases, but standard treatments available to reduce the signs and symptoms to a certain level.