Unseen Passage

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Class 12 HOTs Biology Human Health and Diseases


Question. Why is secondary immune response more intense than the primary immune response in humans?
Answer. Since, the secondary immune response is based on the memory of primary response, i.e. first encounter with antigen. The second generated immune response is more fast having higher affinity for antigen, and therefore more intense than primary immune response.

Question. Name any two types of cells that act as ‘cellular barriers’ to provide innate immunity in humAnswer.
Answer. Certain type of leucocytes (such as PMNL- neutrophils, monocytes) and natural killer cells are two types of cells that act as ‘cellular barriers’ to provide innate immunity in humans

Question. Name the two intermediate hosts on which the human liver fluke depends to complete its life cycle so as to facilitate parasitism of its primary host
Answer. The human liver fluke requires two intermediate hosts, i.e. freshwater snail and fish to complete their life cycle and facilitate parasitism of its primary host

Question. How does haemozoin affect the human body when released in blood during malarial infection?
Answer. The release of toxic haemozoin by the ruptured RBCs during malarial infection accounts for recurrence of high fever and chill every 3-4 days.

Question. What is an autoimmune disease? Give an example.
Answer. The abnormal response of an immune system in which it fails to recognise ‘self and ‘non-self’ and start destroying its own cells and molecules is called autoimmune disease. Rheumatoid is an example of autoimmune disease which destroys articular cartilage and fusing bones

Question. State two different roles of spleen in the human body?
Answer. The two roles of spleen in human body are:
(i) Spleen acts as a filter to trap blood-borne microorganisms.
(ii) It is also a large reservoir of erythrocytes

Question. A boy of ten years had chickenpox. He is not expected to have the same disease for the rest of life. Mention how it is possible?
Answer.(i)The antibodies developed in his body would circulate in body fluids and neutralise the pathogenic agent during subsequent encounters.
(ii) Further memory B-cells and T-cells are retained in the system, which trigger a more intense and quick response against the same antigen, thus preventing the occurrence of same disease in his life

Question. How do virus infected cells provide innate immunity to healthy cells?
Answer. Virus-infected cells secrete proteins called interferons, which protect non-infected cells from viral infection. Thus, providing innate immunity to healthy cells

Question. Mention the useful as well as the harmful drug obtained from the latex of poppy plant.
Answer. Morphine is obtained from latex of poppy plant. It is useful as a sedative and harmful when used as opioids

Question. How does smoking tobacco in human lead to oxygen deficiency in their body?
Answer. Smoking increases carbon monoxide (CO) content in blood and reduces the concentration of haem-bound oxygen. This causes oxygen deficiency in the body


Question. List the symptoms of ascariasis. How does a healthy person acquire this infection?
Answer. The symptoms of ascariasis, caused by roundworm include internal bleeding, muscular pain, fever, anaemia and blockage of intestinal passage A healthy person acquires this infection through consumption of water, vegetables or fruits

Question.A patient showed symptoms of sustained high fever, stomach pain and constipation, but no blood clot in stools. Name the disease and its pathogen. Write the diagnostic test for the disease. How does the disease get transmitted?
Answer. Typhoid is the disease that show symptoms, i.e. high fever, stomach pain and constipation. Its causative agent is Salmonella typhi. Widal test is used for its diagnosis. Typhoid is transmitted through contaminated food and water

Question.(i) Highlight the role of thymus as a lymphoid organ.
(ii) Name the cells that are released from the above-mentioned gland. Mention how they help in immunity?
Answer.(i)Thymus is a primary lymphoid organ of the immune system. Maturation of lymphocytes occur in it. T-cells produced in the bone marrow get mature in thymus and are released from here.
(ii) T-cells are released from thymus, upon maturation. They themselves do not produce antibodies, but help B-cells to produce them. They are also responsible for

Question. (i) Name the group of viruses responsible for causing AIDS in humAnswer. Why are these viruses so named?
(ii) List any two ways of transmission of HIV infection in humans other than sexual contact?
Answer. (i)Retrovirus is the group of viruses causing AIDS in humAnswer. They contain RNA as genetic material and with the help of enzyme reverse transcriptase they make DNA or RNA template. Thus, they are called retrovirus.
(ii) (a) By sharing infected needles.
(b) By transfusion of blood contaminated with HIV

Question. List any two emergent circumstances, when a medical doctor would recommend injection of a pre-formed antibody into the body of a patient and why?
Answer. (i) In case of snake bite, quick immune response is required and we cannot wait for the body to produce antibodies.
(ii) In tetanus, it is infected with some deadly microbes to which quick immune response is required.

Question. How is an allergic reaction caused by an allergen? Name the drug that can reduce the symptoms of allergy?
Answer. Allergens can produce Ig E type of antibodies. There is release of histamine and serotonin like chemicals from mast cells, which cause allergic reactions. The use of drug anti-histamine, adrenalin and steroids quickly reduce the symptoms of allergy.

Question.Identify A, D, E and Fin the diagram of a antibody molecule given below:

Class 12 HOTs Biology Human Health and Diseases

Answer. A-Antigen binding region D-Light chain E -Heavy chain F -Disulphide bond/bridge

Question. Why do normal cells do not show cancerous growth?
Answer. Normal cells do not show cancerous growth as:
(i) Their growth and division are regulated by certain regulatory mechanisms.
(ii) They show the property of contact inhibition, by virtue of which contact with other cells inhibit their uncontrolled growth.

Question. What is ‘withdrawal syndrome’? List any two symptoms it is characterised by.
Answer. If the regular does of drug or alcohol in an addicted person is discontinued abruptly, the body exhibits a characteristic and unpleasant symptom called ‘withdrawal syndrome’, The ‘withdrawal syndrome’ is characterised by symptoms like anxiety, nausea and sweating

Question. How are morphine and heroin related? Mention the effect each one of them has on the human body?
Answer. Both morphine and heroin are extracted from the latex of plant Papaver somniferum. Heroin is actually obtained from acidulation of morphine. Thus, both are related. Morphine acts as an effective sedative and pain killer while heroin acts as depressant and slows down body functions.


Question. Community service department of your school plans a visit to a slum near the school with an objective educate the slum dwellers with respect to health and hygiene.
(i)Why is there a need to organise such visits?
(ii)Write the steps you will highlight, as a member of this department, in your interactions with them to enable them to lead a healthy life.
Answer. (i)Slums are generally unauthorised and encroached colonies with no public facilities and organisation. Due to lack of education, cleanliness and other facilities and the poor living standard in terms of health, hygiene and nutrition such people are always at risk of acquiring infections. Therefore, there is a need to organise visits to slums so as to educate and crate awareness among them regarding the importance of hygiene.
(ii) The points to be highlighted while interacting with the slum people may be.
• Importance of cleanliness and hygiene of body as well as surroundings.
• Awareness and prevention of infectious diseases.
• Use of public facilities, i.e. toiletries.
• Consumption of properly cooked and hygienic food and water.
• Administration of vaccines to new-born children so as to prevent diseases.

Question. (i)Name the causative organisms for the following diseases.
(a) Elephantiasis (b)Ringworm (c)Amoebiasis
(ii)How can public hygiene help control such diseases?
Answer. (i)The causative agent or organism of following diseases are:
(a)Elephantiasis is caused by Wuchereria bancrofti and W. malayi. These affect lower limbs and genital orgAnswer.
(b) Ringworm is caused by Microsporum, Trychophyton and Epidermophyton. They affect the skin, nails and scalp.
(c)Entamoeba histolytica is a protozoan parasite in the large intestine of human, which causes amoebiasis (amoebic dysentery).

(ii) Maintenance of public hygiene such as:
• keeping body and surroundings clean.
• consumption of clean drinking water, fruits and vegetables, etc.
• regular cleaning and disinfection of tanks and other water reservoirs, etc.
• All the above measures help control proper disposal of waste and excreta. The increase in vectors of infectious diseases and their breeding places. Thus, there would be reduced chances of transmission of infectious diseases.

Question.3.Study a part of the life cycle of malarial parasite given below.

Class 12 HOTs Biology Human Health and Diseases

(i)Mention the roles of A in the life cycle of the malarial parasite.
(ii)Name the event C and the organ where this event occurs.
(iii)Identify the organ B and name the cells being released from it.
Answer. (i)A is female Anopheles mosquito, these mosquito act as vectors and transmit the disease from patients to healthy individuals.
(ii) The event C is fertilisation. It occurs in the intestinal wall of mosquito.
(iii) B is salivary glands, sporozoites cells are released from it.

Question. Study the diagram showing replication of HIV in humans and answer the following questions accordingly.

Class 12 HOTs Biology Human Health and Diseases

(i)Write the chemical nature of the coat
(ii)Name the enzyme B acting on X to produce molecule C. Name C.
(iii)Mention the name of the host cell D the HIV attacks first when it enters into the human body.
Answer.(i)A – Protein coat
(ii) B – Reverse transcriptase C – It is viral DNA
(iii) Macrophage (animal or human cell)

Question. Write the source and the effect on the human body of the following drugs.
(i) Morphine
(ii) Cocaine
(iii) Marijuana
Answer.(i)Morphine is obtained from the latex of Papaver somniferum. It is a depressant, which slows down the body functions. (ii)Cocaine is obtained from Erythroxylum coca. It is a stimulant and produces a sense of euphoria and increased energy.
(iii) Marijuana is obtained from the inflorescence of Cannabis sativa. It affects cardiovascular system of the body.

Question. (i) Name the drug used (a) as an effective sedative and pain killer
(b) for helping patients to cope with mental illness like depression but often misused,
(ii) How does moderate and high dosage of cocaine affect the human body?
Answer.(i) (a) Morphine is an effective sedative and pain killer. (b) Lysergic acid diethylamides (LSD) or barbiturates are often misused.
(ii) Moderate dose of cocaine have a stimulating action on central nervous system. It produces a sense of euphoria and increased energy. High dosage of cocaine causes hallucinations

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