Important Questions for Class 12 Chapter 8 - Human Health and Disease

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Important questions based on NCERT syllabus for Chapter 8 - Human Health and Disease:

Question-1: In which way has the study of biology helped us to control infectious diseases?

Solution: The science that makes a study of diseases is called pathology, though in a broad sense it includes diagnostic, prophylactic and curative measures too. Pathology is a study of diseases of all kinds though we will confine ourselves to the diseases caused by a pathogenic organism, the reaction of the host as shown in the form of symptoms, the diagnosis made through a study of their symptoms, etiology of the pathogenic organism and finally steps undertaken to cure the host of its diseases, by eradicating and if it is not possible, by controlling the pathogen. In this way the study of biology helped us to control infectious diseases.

Question-2: What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?

Solution: HIV critically injures the immune system by infecting and eventually killing T-cells. Once the virus has infected a T cell, HIV copies its RNA into double stranded DNA copy by mearis of viral enzyme reverse transcriptase. This process is called reverse transcriptase because it violates the usual way in which genetic information is transcribed. Because reverse transcriptase lacks thg proofreading function that most DNA synthesizing enzymes have, many mutations arises as the virus replicates, further hindering the ability of the immune system to combat the virus. These mutations allow the virus to evolve rapidly resulting in the lost of vital cells. As a result of progressive destruction of its T-cells, the body is easily ravaged by a number of common infectious agents. In many instances, these infections would have caused little injury if there functional T-cells clones available.
Death ultimately results from the relentless attack of opportunistic pathogens or from the body’s inability to fight off malignancies.
virus. These mutations allow the virus to evolve rapidly resulting in the lost of vital cells. As a result of progressive destruction of its T-cells, the body is easily ravaged by a number of common infectious agents. In many instances, these infections would have caused little injury if there functional T-cells clones available.
Death ultimately results from the relentless attack of opportunistic pathogens or from the body’s inability to fight off malignancies.

Question-3: Explain what is meant by metastasis.

Solution: The non-regulated growth of the cells that accompanies cellular transformation produces tumours or neoplasms. Each tumour being the product of proliferation of a single abnormal cell. Malignant tumour cells are cancer cells that spread to mid take up residence in neighbouring tissues – a condition called metastasis.