9th Class (CBSE) Science: Why Do We Fall Ill

Question: Define vaccine and name two vaccines.

Answer: Vaccine is a chemical / drug given in advance to a body to give immunity against certain diseases.
Vaccines given to children are:

1. BCG — for tuberculosis prevention
2. Polio drops — for polio prevention

Question: What is antibiotic penicillin? Give its function.

Answer: Penicillin antibiotic blocks the bacterial processes that build the cell wall. Due to this drug, the bacteria is unable to make a protective cell wall and dies easily. It is used to cure the diseases and infections caused by bacteria.

Question: Bacteria is a cell, antibiotics can kill these bacteria (cell), Human body is also made of cells how does it affect our body?

Answer: Antibiotics block the biochemical pathway of bacteria by which it makes a protective cell wall around it. Antibiotic does not allow the bacteria to make this cell wall because of which they die.

Human body cell don’t make any cell wall so antibiotics cannot have any such effect on our body.

Question: How does cholera becomes an epidemic in a locality?

Answer: Cholera is an infectious disease that spreads due to unsafe water. It can spread in a locality; if a person suffering from cholera lives in the locality and the excreta of this person, get mixed with the drinking water used by people living nearby. The cholera-causing microbe enters the new hosts through the water they drink and cause disease in them.

Question: Name the organs affected due to the following diseases:
Malaria, jaundice, Japanese encephalitis, typhoid.

Answer:

1. Malaria: Infects liver and red blood cells
2. Jaundice: Infects the liver.
3. Japanese encephalitis: Infects the brain
4. Typhoid: Infects blood.

Question: Why are sick patients advised to take bed rest?

Answer: Doctors advise to take bed rest for sick patients so that they can conserve their energy which can be used for healing of their body organs which were affected due to certain disease.

Question: How do we kiU microbes that enter our body and cause diseases?

Answer: Microbes can be killed by using medicines These microbes are of different categories — virus, bacteria, fungi or protozoa. Each of these groups of organisms have some essential biochemical life processes which is peculiar to a particular group and is not shared by others. These pathways are not used by us. By using drugs that blocks the microbial synthesis pathway without affecting us can kill the microbes.

Question: What are disease specific means of prevention?

Answer: The disease specific means of prevention are the use of vaccines. The vaccines, are used against tetanus, diphtheria, whooping cough, measles, polio and many others.

Question: Why can’t we make antiviral medicines / drugs?

Answer: The viruses lie on the border line of living and non-living organisms. The viruses can live, grow and multiply only inside the host body. They cannot be grown or cultured and their .biological pathways cannot be affected. Hence, the antiviral medicines/drugs is difficult to make.