NEET Biology: Biology and Human Welfare · Chapter 1

Human Health and Disease

What to remember

Health is a state of complete physical, mental and social well-being, not just the absence of disease.
Malaria is caused by Plasmodium and spread by the female Anopheles mosquito; sporozoites enter the human, and the rupture of red blood cells releases haemozoin, which causes the fever with chills.
Innate immunity is non-specific and present from birth; acquired immunity is specific, shows memory, and is carried out by B lymphocytes (antibodies) and T lymphocytes (cell-mediated).
HIV is a retrovirus that destroys helper T cells; cancer cells lose contact inhibition and can spread by metastasis; opioids, cannabinoids and coca alkaloids are major drugs of abuse.

Health and disease

Health means a state of complete physical, mental and social well-being. A person is healthy when body functions work properly, when the mind is at peace and when the person gets along well with others.

Disease is the condition in which the normal functioning of one or more organs or systems is affected. Diseases are of two broad kinds.

Infectious diseases are caused by pathogens and can spread from one person to another (for example typhoid, malaria).
Non-infectious diseases do not spread from person to person (for example cancer, which is the most dangerous non-infectious disease).

Common diseases in humans

Typhoid is caused by the bacterium Salmonella typhi. It spreads through contaminated food and water. Symptoms are sustained high fever (39°C to 40°C), weakness, stomach pain, constipation, headache and loss of appetite. In severe cases the intestine may be perforated, which can cause death. The Widal test is used for confirmation. Salmonella enters the small intestine, then reaches other organs through blood.

Pneumonia is caused by Streptococcus pneumoniae and Haemophilus influenzae. These bacteria infect the alveoli of the lungs, which fill with fluid. This leads to serious breathing problems. Symptoms are fever, chills, cough and headache; in severe cases the lips and fingernails turn grey to bluish. The infection spreads by droplets from an infected person and by sharing glasses and utensils.

Common cold is caused by rhinoviruses. It infects the nose and respiratory passage but not the lungs. Symptoms are nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness; it lasts 3 to 7 days. It spreads by droplets from coughs and sneezes, and by contaminated objects.

Amoebiasis (amoebic dysentery) is caused by the protozoan Entamoeba histolytica, which lives in the large intestine. Symptoms are constipation, abdominal pain and cramps, stools with excess mucus and blood clots. Houseflies act as mechanical carriers and spread the parasite to food. Drinking water and food contaminated by faecal matter are the source of infection.

Ascariasis is caused by the intestinal parasite Ascaris (a roundworm). Symptoms are internal bleeding, muscular pain, fever, anaemia and blockage of the intestinal passage. Eggs of the parasite are excreted in the faeces of infected persons and contaminate soil, water and vegetables.

Filariasis (elephantiasis) is caused by filarial worms such as Wuchereria bancrofti and Wuchereria malayi. These worms live in the lymphatic vessels of the lower limbs for many years. They cause chronic inflammation of the organs in which they live, and the limbs and genital organs swell abnormally. The vector is the female Culex mosquito.

Ringworm is a fungal disease caused by the genera Microsporum, Trichophyton and Epidermophyton. Symptoms are dry, scaly lesions on the skin, nails and scalp, with intense itching.

Dengue and chikungunya are viral diseases spread by the Aedes mosquito (Aedes aegypti and Aedes albopictus). Dengue causes high fever, severe headache, pain behind the eyes, joint and muscle pain and rash. Chikungunya causes fever and severe joint pain.

Disease	Pathogen	Type	Transmission or vector	Key feature
Typhoid	Salmonella typhi	Bacterium	Contaminated food and water	Widal test
Pneumonia	Streptococcus pneumoniae, Haemophilus influenzae	Bacteria	Droplets, shared utensils	Alveoli fill with fluid
Common cold	Rhinoviruses	Virus	Droplets, objects	Nose and throat, not lungs
Malaria	Plasmodium species	Protozoan	Female Anopheles	Haemozoin, fever with chills
Amoebiasis	Entamoeba histolytica	Protozoan	Food contaminated by flies	Large intestine, blood in stools
Ascariasis	Ascaris	Roundworm	Eggs in soil and water	Intestinal blockage
Filariasis	Wuchereria bancrofti, W. malayi	Roundworm	Female Culex	Swollen limbs
Ringworm	Microsporum, Trichophyton, Epidermophyton	Fungi	Soil, towels, clothes	Scaly itchy lesions
Dengue, chikungunya	Viruses	Virus	Aedes mosquito	Fever, joint pain

Malaria

Malaria is caused by Plasmodium. Species that infect humans are Plasmodium vivax, Plasmodium malariae and Plasmodium falciparum. Malignant malaria, caused by Plasmodium falciparum, is the most serious and can be fatal.

Life cycle (in words):

1. A female Anopheles mosquito bites a human and injects the infective stage, the sporozoites, into the blood.
2. Sporozoites go to the liver and multiply in liver cells.
3. They attack the red blood cells (RBCs), where they multiply, and the RBCs burst.
4. The bursting of RBCs releases a toxic substance called haemozoin. This causes the characteristic chill and high fever recurring every three to four days.
5. Some parasites form gametocytes in the RBCs.
6. When a female Anopheles bites an infected person, gametocytes enter the mosquito's intestine, where fertilisation and development form sporozoites.
7. The sporozoites move to the salivary glands of the mosquito, ready to infect the next person.

Sequence: Sporozoites (mosquito) → liver cells → RBCs (burst, haemozoin) → gametocytes → mosquito gut → sporozoites in salivary glands. The human is the primary host, where asexual multiplication occurs; the female Anopheles is where the sexual stage is completed.

Prevention and control

Maintain personal and public hygiene: clean drinking water, covered food, safe disposal of waste and excreta, regular cleaning of water tanks and coolers.
Avoid contact with infected persons and do not share utensils or towels.
Control vectors: avoid stagnation of water, use mosquito nets, insecticide sprays, introduce Gambusia (a fish that eats mosquito larvae) in ponds, spray in drains, and use repellents and screens on doors and windows.

Immunity

Immunity is the ability of the body to fight disease-causing organisms. It is of two types: innate and acquired.

Innate immunity is non-specific and present at birth. It has four types of barriers.

Barrier	Examples
Physical	Skin; mucus coating of the epithelium lining the respiratory, gastrointestinal and urogenital tracts
Physiological	Acid in the stomach, saliva in the mouth, tears from the eyes
Cellular	Leucocytes such as neutrophils, monocytes, natural killer cells (lymphocytes) and macrophages
Cytokine	Virus-infected cells secrete interferons, which protect non-infected cells from further viral infection

Acquired immunity is pathogen specific and has memory. The first encounter produces a low-intensity primary response. A later encounter with the same pathogen produces a highly intensified secondary (anamnestic) response, because of memory. The two kinds of lymphocytes involved are B lymphocytes and T lymphocytes. B cells produce a set of proteins called antibodies in response to pathogens in the blood. This is humoral immune response (humoral means in body fluids). T cells do not secrete antibodies but help B cells to produce them. This is the cell-mediated immune response (CMI).

Antibody structure: each antibody molecule has four peptide chains, two small light chains and two longer heavy chains, so it is written H2L2. Types of antibodies are IgA, IgM, IgE, IgG and IgD.

Antibody	Key point
IgA	Found in secretions such as colostrum, tears, saliva and mucus; protects mucosal surfaces
IgM	First antibody produced; large pentamer
IgE	Involved in allergies
IgG	Most abundant; crosses the placenta

Graft rejection: the body can differentiate "self" from "non-self". CMI is responsible for graft rejection, in which a tissue from another person is rejected.

Active and passive immunity, vaccination

Active immunity is produced when the host's own antibodies are made after exposure to antigens, either during natural infection or by antigenic proteins in vaccines. It is slow and takes time to give full effect. Passive immunity is given by ready-made antibodies. The yellowish fluid colostrum, secreted by the mother during the initial days of lactation, has abundant IgA, which gives the infant passive immunity. The foetus also receives antibodies from the mother through the placenta (mainly IgG).

Vaccination: the principle is memory of the immune system. A preparation of inactivated or weakened pathogen (or its antigenic proteins) is introduced into the body. Antibodies produced and memory B and T cells recognise the real pathogen quickly later. Passive immunisation is done when quick response is needed, for example after a tetanus-causing bacterial infection or snake bite, by injecting preformed antibodies (antitoxin). Recombinant DNA technology has produced a vaccine for hepatitis B in yeast. Mass vaccination is called immunisation.

Allergies and autoimmunity

Allergy is the exaggerated response of the immune system to certain antigens present in the environment. The substances causing it are allergens (for example dust, pollen, mites). The antibody involved is IgE. Allergens cause mast cells to release histamine and serotonin, which cause the symptoms of sneezing, watery eyes, running nose and difficulty in breathing. Antihistamine, adrenaline and steroids quickly reduce the symptoms.

Autoimmunity is a condition in which the memory-based acquired immunity attacks the body's own cells, due to genetic and other reasons, causing damage. Rheumatoid arthritis is an example.

The immune system

The immune system includes lymphoid organs, tissues, cells and soluble molecules such as antibodies.

Type	Organs	Function
Primary lymphoid organs	Bone marrow, thymus	Origin and maturation of lymphocytes
Secondary lymphoid organs	Spleen, lymph nodes, tonsils, Peyer's patches of the small intestine, appendix	Sites where lymphocytes interact with antigens and proliferate

Bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced. The thymus is a lobed organ near the heart; it is large at birth but reduces in size with age. Both B and T lymphocytes develop in the bone marrow, but T cells migrate to the thymus to mature. The spleen is a large bean-shaped organ; it mainly contains lymphocytes and phagocytes and filters blood, trapping blood-borne microorganisms. Lymph nodes trap microorganisms in the lymph. Mucosal-associated lymphoid tissue (MALT) is located within the lining of the major tracts (respiratory, digestive and urogenital) and constitutes about 50 per cent of the lymphoid tissue in the human body.

AIDS

AIDS is acquired immuno deficiency syndrome. It is caused by the Human Immuno-deficiency Virus (HIV), a retrovirus with an RNA genome.

Transmission: sexual contact with an infected person; transfusion of contaminated blood and blood products; sharing of infected needles; from an infected mother to her child through the placenta. HIV does not spread by touch, handshake or sharing of food.

Replication cycle: HIV enters the macrophages (and helper T cells). The viral RNA is converted into viral DNA by reverse transcriptase. This DNA gets incorporated into the host cell DNA and directs the infected cells to produce virus particles. The macrophages continue to produce virus and act as an HIV factory. Meanwhile, HIV enters helper T lymphocytes (TH), replicates and produces progeny viruses, which attack other helper T cells. The number of helper T cells decreases progressively. The person becomes immune-deficient and suffers from infections by bacteria such as Mycobacterium, viruses, fungi and parasites such as Toxoplasma.

Diagnosis uses ELISA (enzyme linked immuno-sorbent assay). Treatment with anti-retroviral drugs is only partially effective; it prolongs life but cannot prevent death. There is no cure, so prevention is important.

Prevention: make blood safe, use disposable needles and syringes, use condoms, free distribution of condoms, controlling drug abuse, advocating safe sex and regular check-ups. NACO (National AIDS Control Organisation) and other non-governmental organisations (NGOs) are working to educate people.

Cancer

Cancer is one of the most dreaded diseases. Normal cells show contact inhibition, which is the property by which contact with other cells inhibits their uncontrolled growth. Cancer cells have lost this property, so they divide continuously and form a mass of cells called a tumour.

Benign tumours remain confined to the place of origin, do not spread to other parts and cause little damage.
Malignant tumours are masses of proliferating cells called neoplastic or tumour cells; they grow very rapidly, invade and damage the surrounding normal tissues. Cells sloughed from such tumours reach other sites through blood, where they form a new tumour. This spread is called metastasis.

Causes: transformation of normal cells to cancerous cells may be induced by physical, chemical or biological agents called carcinogens. Ionising radiation such as X-rays and gamma rays and non-ionising radiation such as UV cause DNA damage. Chemical carcinogens include tobacco smoke, which is a major cause of lung cancer. Oncogenic viruses have genes called viral oncogenes. In normal cells there are genes called cellular oncogenes (c-onc) or proto-oncogenes; when activated under certain conditions, they lead to oncogenic transformation.

Detection and diagnosis: biopsy and histopathological studies of the tissue, blood and bone marrow tests for increased cell counts in leukaemia. Techniques include radiography (X-rays), CT scan (computed tomography) and MRI (magnetic resonance imaging). Antibodies against cancer-specific antigens are also used.

Treatment: surgery, radiation therapy and chemotherapy. Some cancers are treated with biological response modifiers such as alpha-interferon, which activates the immune system and helps destroy the tumour.

Drugs and alcohol abuse

Drugs that are commonly abused are opioids, cannabinoids and coca alkaloids; many are also used as medicines.

Class	Source	Effect
Opioids (morphine, heroin or smack)	Latex of poppy plant Papaver somniferum	Bind to opioid receptors in the central nervous system and gastrointestinal tract; act as depressant and slow body functions. Heroin is diacetylmorphine, made by acetylation of morphine
Cannabinoids	Inflorescence of Cannabis sativa (marijuana, hashish, charas, ganja)	Interact with cannabinoid receptors, mainly in the brain; affect cardiovascular system
Coca alkaloids (cocaine)	Coca plant Erythroxylum coca	Interferes with the transport of the neurotransmitter dopamine; stimulates the central nervous system, causes euphoria and hallucinations

Morphine is a sedative and painkiller used in surgery.

Adolescence is the period of 12 to 18 years, a bridge between childhood and adulthood. Curiosity, need for adventure and excitement, and experimentation, along with peer pressure, stress and media influence, lead to the first use. Addiction is a psychological attachment to the effects such as euphoria. Dependence is the tendency of the body to manifest a characteristic and unpleasant withdrawal syndrome if the use is abruptly stopped. Effects of alcohol include reckless behaviour, vandalism and violence; it damages the nervous system and the liver (cirrhosis). Sharing of needles in injecting drugs spreads AIDS and hepatitis B.

Prevention and control: avoid undue peer pressure, educate and counsel, seek help from parents and peers, look for danger signs, and seek professional and medical help.

NEET traps

1. Salmonella typhi causes typhoid and is tested by the Widal test; Streptococcus pneumoniae causes pneumonia.
2. Rhinoviruses infect the nose and upper respiratory passage but not the lungs; pneumonia bacteria infect the alveoli.
3. Haemozoin is released when RBCs burst, not when sporozoites enter the liver.
4. The infective stage for humans is the sporozoite; the stage that infects the mosquito is the gametocyte.
5. Malaria vector is Anopheles; filariasis vector is Culex; dengue and chikungunya vector is Aedes.
6. Entamoeba histolytica is carried by houseflies mechanically; there is no vector in which it develops.
7. Humoral immunity involves B cells and antibodies; cell-mediated immunity involves T cells and causes graft rejection.
8. Colostrum IgA gives passive immunity; infection or a vaccine gives active immunity.
9. IgE is linked to allergy; IgM is the first antibody; IgG crosses the placenta.
10. HIV is an RNA virus that makes DNA with reverse transcriptase; the target is the helper T cell.

One-liners

1. Health is a state of complete physical, mental and social well-being.
2. Widal test confirms typhoid.
3. Plasmodium falciparum causes the most serious malaria.
4. Haemozoin causes chill and fever in malaria.
5. Female Anopheles is the vector of malaria.
6. Wuchereria causes filariasis, also called elephantiasis.
7. Ringworm is caused by Microsporum, Trichophyton and Epidermophyton.
8. Interferons are the cytokine barrier of innate immunity.
9. An antibody has two heavy and two light chains.
10. Secondary immune response is faster and stronger than primary response.
11. Bone marrow and thymus are the primary lymphoid organs.
12. MALT makes up about 50 per cent of the lymphoid tissue of the body.
13. ELISA is used to diagnose AIDS.
14. Cancer cells lose contact inhibition.
15. Morphine is obtained from the latex of Papaver somniferum.

Practice questions

The Widal test is used to confirm which disease?
1. Malaria
2. Typhoid
3. Dengue
4. Pneumonia
Answer
B. Typhoid
The Widal test is used to confirm typhoid, caused by Salmonella typhi.
Which stage of Plasmodium is injected into the human blood by a female Anopheles mosquito?
1. Eggs
2. Haemozoin
3. Sporozoites
4. Gametocytes
Answer
C. Sporozoites
The infective stage injected by the mosquito is the sporozoite.
The vector of filariasis is
1. Culex
2. Housefly
3. Aedes
4. Anopheles
Answer
A. Culex
Filariasis caused by Wuchereria is spread by the female Culex mosquito.
Haemozoin, the toxic substance responsible for the chill and fever of malaria, is released when
1. sporozoites enter the liver
2. parasites enter the salivary glands
3. gametocytes enter the mosquito
4. red blood cells burst
Answer
D. red blood cells burst
Haemozoin is released on the bursting of RBCs.
Which pair of bacteria causes pneumonia in humans?
1. Streptococcus pneumoniae and Haemophilus influenzae
2. Streptococcus pneumoniae and Salmonella typhi
3. Trichophyton and Streptococcus pneumoniae
4. Salmonella typhi and Haemophilus influenzae
Answer
A. Streptococcus pneumoniae and Haemophilus influenzae
Pneumonia is caused by Streptococcus pneumoniae and Haemophilus influenzae, which infect the alveoli.
Interferons secreted by virus-infected cells form which barrier of innate immunity?
1. Cellular barrier
2. Physical barrier
3. Physiological barrier
4. Cytokine barrier
Answer
D. Cytokine barrier
Interferons are cytokines that protect non-infected cells from viral infection.
Which antibody class is the most abundant in blood and crosses the placenta to the foetus?
1. IgA
2. IgM
3. IgG
4. IgE
Answer
C. IgG
IgG crosses the placenta and gives the foetus passive immunity.
The antibody present in large amounts in colostrum is
1. IgE
2. IgA
3. IgD
4. IgM
Answer
B. IgA
Colostrum is rich in IgA, which gives passive immunity to the infant.
Which of the following are primary lymphoid organs?
1. Spleen and lymph nodes
2. Bone marrow and thymus
3. Peyer's patches and spleen
4. Tonsils and appendix
Answer
B. Bone marrow and thymus
Lymphocytes originate and mature in the bone marrow and thymus.
Mucosal-associated lymphoid tissue (MALT) forms about what part of the lymphoid tissue of the human body?
1. 25 per cent
2. 10 per cent
3. 75 per cent
4. 50 per cent
Answer
D. 50 per cent
MALT forms about 50 per cent of the lymphoid tissue.
In the HIV replication cycle, viral RNA is changed into viral DNA by
1. reverse transcriptase
2. ligase
3. DNA polymerase of the host
4. RNA polymerase
Answer
A. reverse transcriptase
HIV is a retrovirus; reverse transcriptase makes DNA from its RNA.
The spread of cells from a malignant tumour to distant sites through blood is called
1. contact inhibition
2. transformation
3. metastasis
4. benign growth
Answer
C. metastasis
Spread of tumour cells to other sites is metastasis.
Heroin (smack) is obtained from
1. Cannabis sativa
2. Atropa belladonna
3. Erythroxylum coca
4. Papaver somniferum
Answer
D. Papaver somniferum
Heroin is made by acetylation of morphine, which comes from the latex of Papaver somniferum.
Cocaine acts by interfering with the transport of which neurotransmitter?
1. Serotonin
2. Adrenaline
3. Dopamine
4. Acetylcholine
Answer
C. Dopamine
Cocaine interferes with the transport of dopamine.
Ringworm is caused by fungi belonging to the genera
1. Plasmodium, Entamoeba and Rhinovirus
2. Microsporum, Trichophyton and Epidermophyton
3. Salmonella, Ascaris and Wuchereria
4. Aspergillus, Penicillium and Rhizopus
Answer
B. Microsporum, Trichophyton and Epidermophyton
Ringworm is caused by Microsporum, Trichophyton and Epidermophyton.
Which of these causes the common cold?
1. Rhinoviruses
2. Entamoeba histolytica
3. Aedes virus
4. Haemophilus influenzae
Answer
A. Rhinoviruses
The common cold is caused by rhinoviruses, which infect the nose and upper respiratory tract.
Given below are two statements: Statement I: Entamoeba histolytica lives in the large intestine of humans. Statement II: Houseflies act as mechanical carriers of Entamoeba histolytica.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
A. Both Statement I and Statement II are correct
Both are correct.
Given below are two statements: Statement I: Typhoid is caused by Salmonella typhi. Statement II: The Widal test is used to detect HIV infection.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
C. Statement I is correct but Statement II is incorrect
The Widal test is for typhoid; ELISA is used for HIV.
Given below are two statements: Statement I: Ascaris causes filariasis. Statement II: Wuchereria lives in the lymphatic vessels of the lower limbs.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
D. Statement I is incorrect but Statement II is correct
Filariasis is caused by Wuchereria; Ascaris causes ascariasis.
Given below are two statements: Statement I: Humoral immunity is mediated by T lymphocytes. Statement II: Cell-mediated immunity is responsible for graft rejection.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
D. Statement I is incorrect but Statement II is correct
Humoral immunity is by B cells and antibodies; CMI causes graft rejection.
Given below are two statements: Statement I: The primary immune response is of low intensity. Statement II: The secondary immune response is also of low intensity.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
C. Statement I is correct but Statement II is incorrect
The secondary response is highly intensified because of memory.
Which of the following statements are correct? 1. The thymus is large at birth and reduces in size with age. 2. The spleen filters blood and traps blood-borne microorganisms. 3. Lymph nodes are primary lymphoid organs.
1. 1 and 2 only
2. 2 and 3 only
3. 1 and 3 only
4. 1, 2 and 3
Answer
A. 1 and 2 only
Lymph nodes are secondary lymphoid organs, so only 1 and 2 are correct.
Which of the following statements are correct? 1. HIV is a DNA virus. 2. HIV spreads by a handshake. 3. HIV infects helper T lymphocytes.
1. 1 and 2 only
2. 3 only
3. 2 and 3 only
4. 1 and 3 only
Answer
B. 3 only
HIV is an RNA retrovirus and does not spread by touch; only 3 is correct.
Given below are two statements: Statement I: Benign tumours spread to distant parts of the body. Statement II: Malignant tumours remain confined to their place of origin.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
B. Both Statement I and Statement II are incorrect
The two descriptions are reversed; both are incorrect.
Given below are two statements: Statement I: Active immunity is produced by the IgA of colostrum. Statement II: Passive immunity is given by ready-made antibodies.
1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct
Answer
D. Statement I is incorrect but Statement II is correct
Colostrum IgA gives passive immunity; so Statement I is incorrect.
Which of the following statements are correct? 1. Morphine is obtained from Cannabis sativa. 2. Cocaine is obtained from Erythroxylum coca. 3. Heroin is diacetylmorphine.
1. 1 and 2 only
2. 1 and 3 only
3. 2 and 3 only
4. 1, 2 and 3
Answer
C. 2 and 3 only
Morphine comes from Papaver somniferum; 2 and 3 are correct.
Assertion (A): In malaria, fever with chills recurs at regular intervals. Reason (R): Haemozoin is released when red blood cells burst.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
A. Both A and R are true and R is the correct explanation of A
Release of haemozoin on RBC rupture causes the fever and chills.
Assertion (A): Cancer cells form a mass called a tumour. Reason (R): Cancer cells retain contact inhibition.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
C. A is true but R is false
Cancer cells have lost contact inhibition, hence they form a tumour.
Assertion (A): Heroin acts as a depressant of the nervous system. Reason (R): Heroin is obtained from the latex of the poppy plant.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
B. Both A and R are true but R is not the correct explanation of A
Both are true, but the source does not explain the depressant action, which is due to binding to opioid receptors.
Assertion (A): The Aedes mosquito spreads malaria. Reason (R): Aedes aegypti is a vector of dengue.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
D. A is false but R is true
Malaria is spread by Anopheles, not Aedes; the reason is true.
Assertion (A): HIV is a retrovirus. Reason (R): It converts its RNA genome into DNA using reverse transcriptase.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
A. Both A and R are true and R is the correct explanation of A
This is the defining feature of a retrovirus.
Assertion (A): Both B and T lymphocytes mature in the thymus. Reason (R): The thymus is a primary lymphoid organ.
1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true
Answer
D. A is false but R is true
B cells mature in the bone marrow; only T cells mature in the thymus.
Match List I with List II. List I: a. Salmonella typhi b. Entamoeba histolytica c. Wuchereria d. Rhinovirus List II: i. Common cold ii. Typhoid iii. Amoebiasis iv. Filariasis
1. a-i, b-iii, c-iv, d-ii
2. a-ii, b-iii, c-iv, d-i
3. a-iii, b-ii, c-iv, d-i
4. a-ii, b-iii, c-i, d-iv
Answer
B. a-ii, b-iii, c-iv, d-i
Pathogen to disease: a-ii, b-iii, c-iv, d-i.
Match List I with List II. List I: a. IgA b. IgM c. IgE d. IgG List II: i. Allergy ii. Colostrum iii. First antibody produced iv. Crosses the placenta
1. a-i, b-iii, c-ii, d-iv
2. a-ii, b-i, c-iii, d-iv
3. a-ii, b-iii, c-i, d-iv
4. a-iii, b-ii, c-i, d-iv
Answer
C. a-ii, b-iii, c-i, d-iv
IgA: colostrum (ii); IgM: first (iii); IgE: allergy (i); IgG: crosses placenta (iv).
Match List I with List II. List I: a. Anopheles b. Culex c. Aedes d. Housefly List II: i. Filariasis ii. Dengue iii. Malaria iv. Mechanical carrier of Entamoeba
1. a-iii, b-ii, c-i, d-iv
2. a-iii, b-i, c-ii, d-iv
3. a-i, b-iii, c-ii, d-iv
4. a-iii, b-i, c-iv, d-ii
Answer
B. a-iii, b-i, c-ii, d-iv
Anopheles: malaria; Culex: filariasis; Aedes: dengue; housefly: carries Entamoeba.
Match List I with List II. List I: a. Morphine b. Cocaine c. Marijuana d. Heroin List II: i. Inflorescence of Cannabis sativa ii. Coca plant iii. Latex of poppy iv. Diacetylmorphine
1. a-iii, b-ii, c-i, d-iv
2. a-iii, b-i, c-ii, d-iv
3. a-iii, b-ii, c-iv, d-i
4. a-ii, b-iii, c-i, d-iv
Answer
A. a-iii, b-ii, c-i, d-iv
Morphine: poppy latex; cocaine: coca plant; marijuana: Cannabis; heroin: diacetylmorphine.
Match List I with List II. List I: a. Thymus b. Spleen c. Peyer's patches d. Bone marrow List II: i. Small intestine ii. Origin of all blood cells iii. Lobed organ near the heart iv. Bean-shaped organ that filters blood
1. a-iii, b-iv, c-i, d-ii
2. a-iii, b-i, c-iv, d-ii
3. a-iv, b-iii, c-i, d-ii
4. a-iii, b-iv, c-ii, d-i
Answer
A. a-iii, b-iv, c-i, d-ii
Thymus: lobed organ near heart; spleen: filters blood; Peyer's patches: small intestine; bone marrow: origin of blood cells.
Match List I with List II. List I: a. Contact inhibition b. Metastasis c. Biopsy d. Alpha-interferon List II: i. Spread to distant sites ii. Histopathological study iii. Biological response modifier iv. Property lost by cancer cells
1. a-iv, b-ii, c-i, d-iii
2. a-iv, b-i, c-ii, d-iii
3. a-i, b-iv, c-ii, d-iii
4. a-iv, b-i, c-iii, d-ii
Answer
B. a-iv, b-i, c-ii, d-iii
Contact inhibition is lost in cancer (iv); metastasis is spread (i); biopsy is histopathology (ii); alpha-interferon is a modifier (iii).
A patient has high fever with chills every three to four days. Which substance released from burst red blood cells causes these symptoms?
1. Interferon
2. Histamine
3. Serotonin
4. Haemozoin
Answer
D. Haemozoin
In malaria, haemozoin from ruptured RBCs causes chills and fever.
A person bitten by a snake is given an injection of ready-made antibodies. This is an example of
1. active immunity
2. autoimmunity
3. passive immunisation
4. innate immunity
Answer
C. passive immunisation
Preformed antibodies give quick, passive immunity.
After exposure to pollen, a person develops sneezing and watery eyes. Which cells release the chemicals responsible?
1. Mast cells
2. Neutrophils
3. Helper T cells
4. Natural killer cells
Answer
A. Mast cells
IgE-linked allergens make mast cells release histamine and serotonin.
A patient's transplanted kidney is rejected after some weeks. Which cells mainly bring about this rejection?
1. Red blood cells
2. T lymphocytes
3. Neutrophils
4. B cells making IgE
Answer
B. T lymphocytes
Graft rejection is by cell-mediated immunity, carried out by T cells.
A person tests positive for HIV by ELISA. Which cell count will fall progressively in this person?
1. Red blood cells
2. Mast cells
3. Platelets
4. Helper T lymphocytes
Answer
D. Helper T lymphocytes
HIV multiplies in helper T cells and destroys them.
A child has sustained high fever (39°C to 40°C), constipation and stomach pain, and the Widal test is positive. In severe cases, which organ may be perforated?
1. Lungs
2. Lymph vessels
3. Intestine
4. Skin
Answer
C. Intestine
Typhoid can perforate the intestine.
Cells shed from a tumour in the breast travel through blood and form a new tumour in the liver. The original tumour is
1. non-infectious and not harmful
2. benign and shows metastasis
3. malignant and has metastasised
4. benign and shows contact inhibition
Answer
C. malignant and has metastasised
Spread to other sites by blood is metastasis, a feature of malignant tumours.

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1.The cause of Hepatitis A is a:
2.The blood pressure of a young male human being is normally -
3.Who invented the small pox vaccine?
4.The gland in the human body which secretes both enzymes and hormones is:
5.The friction in liquids is called:
6.The first human gene therapy experiment, which began in September 1990, used a retroviral vector against which deficiency?
7.The disease related with apple is known as:
8.The EEG (electroencephalogram) test is conducted for diagnosing ailments of which of the following organs?
9.The disease which wiped out one third of the population of Europe in the 12th and 13th centuries was-
10.The disease caused by deficiency of protein in children is called-

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