VBQs Human Health and Diseases Class 12 Biology

VBQs for Class 12

VBQs Human Health and Diseases Class 12 Biology with solutions has been provided below for standard students. We have provided chapter wise VBQ for Class 12 Biology with solutions. The following Human Health and Diseases Class 12 Biology value based questions with answers will come in your exams. Students should understand the concepts and learn the solved cased based VBQs provided below. This will help you to get better marks in class 12 examinations.

Human Health and Diseases VBQs Class 12 Biology

Very Short Answer Type Questions

Question. Retroviruses have no DNA. However the DNA of the infected host cell does possess the viral DNA.
How is it possible?
Answer :
After infecting the host cell, the viral RNA undergoes reverse transcription in the presence
of an enzyme reverse transcriptase as a result of which viral DNA is formed. This DNA then gets
incorporated into infected host DNA.

Question. How do cytokinin barriers provide innate immunity in humans?
How do cytokine barriers help in evading viral infections ? 
Answer :
Interferon (proteins), secreted by virus infected cells (protect non-infected cells from further viral infection).
Detailed Answer:
Virus infected cells secrete proteins called interferons, which are low molecular weight proteins and act as cytokine barriers. They protect non-infected cells from further infection.

Question. Why is colostrum a boon to the newborn baby ?
Answer :
Colostrum (Mother’s first milk) contains good amount of antibodies like IgA, which provide passive immunity to the new born and protects it from various infections.

Question. What is an autoimmune disease ?
What is an autoimmune disease ? Give an example.
Answer :
Autoimmune disease is a condition of the body in which the immune system of the body attacks self cells e.g. rheumatoid arthritis. 

Question. How does haemozoin affect the human body when released in blood during malarial infection ? 
Answer :
Hemozoin is a toxic substance released by rupturing of RBCs in to blood during malarial infection. It causes chill and high fever, recurring every 3 – 4 days / in cyclic manner.

Question. Name the two intermediate hosts which the human liver fluke depends on to complete its life cycle so as to facilitate parasitization of its primary host. 
Answer :
Terrestrial snail and fish are two intermediate hosts on which the human liver fluke depends to complete its life cycle so as to facilitate parasitization of its primary host. 

Question. Why sharing of injection needles between two individuals is not recommended ?
Answer :
Sharing of injection needles is not recommended so as to avoid the transmission of STDs like AIDS and Hepatitis from the diseased person to the healthy person. 

Question. How does malaria differ from chikungunya with reference to their vectors.
Answer :
The vector of malaria is Anopheles mosquito while that of chikungunya is Aedes mosquito. 

Question. Name the condition in vertebrates where the body attacks self-cells.
Answer :
Auto immune disorder or auto-immune disease.

Question. Name the stage of Plasmodium that gains entry into the human when bitten by an infected female Anopheles. 
Answer :

Question. A patient is down with Amoebiasis. List the symptoms that confirm this infection. Name the causative pathogen. 
Answer :
Constipation, abdominal pain, stools with mucous, blood clot.
Entamoeba histolytica. 

Question. State the function of mast cells in allergy response.
Answer :
The chemicals like histamine and serotonin are released from mast cells. These chemicals cause exaggerated response of immune system called allergy response. 

Question. It was diagnosed by a specialist that the immune system of the body of a patient has been suppressed. Name the disease the patient is suffering and its causative agent.
Answer :
The name of such a disease is AIDS (Acquired Immunodeficiency Syndrome) and it is caused by HIV (Human Immunodeficiency Virus). 

Short Answer Type Questions

Question. (i) Name any two helminths which are known to be pathogenic to human.
(ii) List two symptoms of the diseases caused by any one of them.
Answer :
 (i) Ascaris, Wuchereria
(ii) Symptoms-internal bleeding, muscular pain, fever, anaemia, blockage of the internal passage (any two) / chronic inflammation of the organs, deformities in genital organs.
Detailed Answer :
(i) Two helminths pathogenic to humans are :
(a) Ascaris–Causing ascariasis disease in humans.
(b) Wuchereria bancrofti & W. malayi causing Filariasis or elephantasis in humans.
Symptoms of Ascariasis : Internal bleeding, muscular pain, anaemia, blockage of intestinal passage.
Symptoms of Filariasis : Chronic inflammation of lymphatic vessels of lower limbs and gross deformities of genital organs.

Question. How are oncogenic viruses different from protooncogenes?
Answer :
 Oncogenic viruses are cancer causing viruses / external cancer causing factor.
Proto-oncogenes: Identified in normal cells which when activated (under certain condition) could lead to oncogenic transformation of cells / internal cancer causing factor. 

Question. Name the cells HIV (Human Immunodeficiency Virus) gains entry into after infecting the human body. Explain the events that occur in these cells.
Answer :
 HIV (Human immune deficiency virus) enters into macrophages after getting in human body.
HIV multiplies first in macrophages and then in helper T cells or lymphocytes.
Events that occur in the human host after the entry of HIV :
(i) After entering the human body, the HIV virus attacks and enters the macrophages.
(ii) Inside the macrophages, the RNA of the virus replicates with the help of enzyme reverse transcriptase and give rise to viral DNA.
(iii) Then, this viral DNA incorporates into the host cell DNA, uses raw materials and infected cell machinery and directs the synthesis of virus particles.
(iv) At the same time, HIV enters the helper T-lymphocytes, replicates and produce progenies.
(v) As a result, T-lymphocytes start decreasing in number and immune response of the person becomes weak. 

Question. Name the type of immunity the colostrum provides to a newborn baby. Write giving an example where this type of immunity should be provided to a person. 
Answer :
 Passive Immunity 
In case of infection by deadly microbes (tetanus) or snake bite where quick immune response is required.
Detailed Answer :
When ready made antibodies are directly given to protect the body against foreign agents, it is called passive immunity.
To neutralize snake venom or deadly microbe infection (tetanus), quick immunity should be provided to a person.

Question. State the role of T-lymphocytes and B-lymphocytes in developing acquired immunity against certain diseases.
Answer :
 The cells responsible for producing the acquired immune response in human body are two special types of lymphocytes called as T-lymphocytes and B-lymphocytes.
T-lymphocytes help B-lymphocytes to produce antibodies or CMI (cell mediated immunity).
B-lymphocytes produce antibodies into blood to fight antigens. 

Question. A patient showed symptoms of constipation, abdominal pain and stools with excess mucous and blood clots. Name the disease and its pathogen. Where do these pathogens live in the victim’s body ?
Name the mechanical carrier that transmits this parasite.
Answer :
 Disease – Amoebiasis.
Pathogen – Entamoeba histolytica.
The pathogen resides in the large intestine.
Carrier– Houseflies. 

Question. Explain the impact of removal of thymus gland on the immune system of a human body.
Answer :
 The thymus provides micro-environments for the development and maturation of T-lymphocytes.
The T-cells themselves do not secrete antibodies but they help B cells to produce them. Therefore, the immunity will be reduced.

Question. Name the parasite that causes filariasis in humans.
Mention its two diagnostic symptoms. How is this disease transmitted to others ?
Answer : Filariasis is caused by two types of parasitic worms:
Wuchereria bancrofti and Wuchereria malayi.
Symptoms : Chronic inflammation of the lymphatic vessels of the lower limbs and gross deformities of genital organs.
This disease is transmitted through the bite of female mosquito vectors, i.e., Culex mosquito.

Question. Name the cells that act as HIV factory in humans when infected by HIV. Explain events that occur in the infected cell.
Answer :
 Macrophages / Helper T-cells act as HIV factory.
The virus enters macrophages or helper T-cells where RNA genome of the virus replicates to form viral DNA with the help of the enzyme reverse transcriptase. The viral DNA then gets incorporated into host cell’s DNA and directs infected cells to produce virus particles. The macrophages continue to produces virus particles. Simultaneously the virus enters the helper T-cells where it replicates and form progeny viruses. Progeny viruses released in the blood attack other helper T-cells with the result these member goes on decreasing in the infected person. Due to the fall in their number, the antibodies are not produced by B-lymphocytes to fight with the pathogen / antigens, which results in the infected person becoming immunodeficient and he is not able to protect himself from any type of infection. 

Question. Name the two types of immune systems in a human body. Why are cell mediated and humoral immunities so called ?
Answer :
 Two types of immune systems in a human body are acquired and innate. 
Cell mediated immunity is called so because cells like T-lymphocytes provide immunity / T-cells kill or destroy the antigens.
Humoral immunity or antibody mediated immunity is called so because it consists of antibodies that are present in humours or body fluids such as plasma, lymph and external secretions whereas cell-mediated immunity is provided by B-cells and T-cells. 

Question. Why is the structure of an antibody molecule represented as H2L2 ? Name any two types of antibodies produced in a human body.
Answer :
 L2 = Two light / small polypeptide chains, H2= two heavy / longer polypeptide chains. 
IgA / IgM / IgE / IgG. (Any two) 

Question. Write the scientific names of the causal organisms of elephantiasis and ringworm in humans.
Mention the body parts affected by them.
Answer :
 Elephantiasis is caused by Wuchereria bancrofti and Wuchereria malayi. Legs/scrotum/lymphatic vessels or lower limb. 
Ringworm is caused by Trichophyton / Microsporum / Epidermophyton, Skin, nails and scalp. 

Question. How is an allergic reaction caused by an allergen ? Name a drug that can reduce the symptoms of allergy.
Answer :
 (i) Allergy is due to the release of chemicals like histamine and serotonin from the mast cells.
Common examples of allergens are mites in dust, pollens, animal dander etc.
(ii) The use of drugs like anti-histamine, adrenaline and steroids quickly reduces the symptoms of allergy. 

Question. List any two emergent circumstances when a medical doctor would recommend injection of a preformed antibody into the body of a patient and why ?
Answer :
 (i) If a person is infected with some deadly microbes, a quick immune response is required as in tetanus, we need to directly inject the preformed antibodies or antitoxin.
(ii) Even in case of snake bites, the injection given to the patients contains preformed antibodies against the snake venom.
This type of immunization is called passive immunization. 

Question. Mention one application for each of the following :
(i) Passive immunization
(ii) Anti-histamine
(iii) Colostrum
(iv) Cytokine-barrier
Answer :
 (i) Provide preformed antibodies / anti-toxins for quick response in case of infection by deadly microbes (tetanus) or snake bite. 
(ii) Reduces symptoms of allergy. 
(iii) Provides passive immunity / antibodies / Ig A to new born.
(iv) Protection of non-infected cells from further viral infection. 

Question. Certain attributes of innate immunity are given in the table below. Identify A, B, C, D, E and F respectively in it.

VBQs Human Health and Diseases Class 12 Biology

Answer : A. Physiological barrier.
B. Acid in Stomach/Saliva in mouth/Tears.
C. Cellular Barrier.
D. Phagocytose/Destroy microbes.
E. Interferons.
F. Protect non-infected cells from virus attack.

Question. Name a human disease, its causal organism, symptoms (any three) and vector, spread by intake of water and food contaminated by human faecal- matter.
Answer :
Amoebiasis (Amoebic dysentery), Entamaeba histolytica, constipation, abdominal pain, cramps, stool with excess muscus, blood clots (Any three symptoms), Housefly.
Ascariasis, Ascaris, internal bleeding, muscular pain, fever, anaemia, blockage of intestinal passage (Any three symptoms), Housefly.
Typhoid, Salmonella typhi, high fever, weakness, stomach pain, constipation, headache, loss of appetite (Any three symptoms), Housefly. 

Question. How are primary and secondary immune responses carried out in the human body? Explain 
Answer :
Primary response–when the body encounters a pathogen, for the first time it produces the primary response, which is of low in intensity but the memory of this encounter with the pathogen in formed and maintained. 
Secondary response-subsequent encounter with the same pathogen, elicits a highly intensified secondary response, based on memory of immune system. 

Question. Medically it is advised to all young mothers that breastfeeding is the best for their newborn babies. Do you agree? Give reasons in support of your answer.
Why is breast feeding recommended during the initial period of an infant’s growth ? Give reasons.
Answer :
Provides nutrition (calcium, fats, lactose) / provides (passive) immunity / provides antibodies / Ig A. 
Detailed Answer :
Breast-feeding is recommended during the initial period of an infant’s growth as :
(i) It provides passive immunity to the baby through colostrum.
(ii) It provides a balanced nutrition to the baby.
(iii) Also, it protects baby from allergens. 

Question. A farmer while working or his farm was bitten
by a poisonous snake. The workers in the farm immediately rushed him to the nearby health centre. The doctor right away gave him an injection to save his life. What did the doctor inject and why ? Explain.
Answer :
(i) Antitoxin / Antivenoms / Preformed antibodies. 
(ii) Whenever quick immune response is required we need to directly inject preformed antibodies / Antitoxins. 
(iii) To neutralize snake venom quickly passive immunity is provided.