31. The first barrier to invasion is b. intact skin and body cavity linings c. d

Question

31. The first barrier to invasion is b. intact skin and body cavity linings c. direct attack by white blood cells d. Innate immunity e· development of memory cel s. 32 Joe Smith had the flu last year. This winter he "caught the flu again Why wasn't he immune the second time? a Memory cels produced in response to viral Iinfections only last for a short period of time, usually only several weeks b. Joe obviously has a weak immune system c. Many viruses, such as influenza viruses are able to rapidly change their surface antigens thereby avoiding the previously produced memory cels d Memory cells are only efflective against bacteria and protozoans and are not able to recognize viral antigen. e None of the above explain why Joe caught to the flu this year 33. Vaccines contain a. T cells programmed to attack the pathogen. b. memory cells against the pathogen. c. lymphokines d. antibodies of the pathogen e. antigens of the pathogen. 34. Antibodies a. Are cells b. Are created in our body c. Can be taken as a pill d. Are made of lipids e. Are made from antibiotics 35. Antibiotics: a. Are proteins b. Make antibodies c. Kil viruses d. Kill bactería e. All of the above 36. Antigens: Are made of fungus Can be taken as a pill Can be used to make vaccines Are cells Are antibodies a. b. c. d. e. 37. A virus is non-living because it requires a cell to: a. metabolize b. reproduce C. respond to stimuli d. maintain homeostasis 38. A flu vaccination must be given to a person every year because a. It is too strong to stay in your body forever b. The vaccine dies after a certain period of time. c. The virus can change from one year to the next 39. What of the following is ordered from LARGEST to SMALLEST? a. mitochondrion, hemoglobin, virus, glucose, water molecule b. virus, mitochondrion, hemoglobin, glucose, water molecule C. mtochondnon, virus, hemoglobin, glucose, water molecule d. virus, mitochondrion, glucose, hemoglobin, water molecule

Explanation / Answer

31) The answer will be intact skin & body cavity linings (Option b).

Reason: Antibody production, direct attack by white blood cells & development of memory cells- all these occur after invasion already occurs. So, we can ignore options a, c & e. Innate immunity also includes natural killer cells, mast cells, eosinophil etc. which become active after invasion already taken place. So, we can ignore option d. Skin & body cavity linings provide first line of defence against any invasion. So, the correct answer will be option b.

32) The answer will be many viruses, such as influenza viruses are able to rapidly change their surface antigens thereby avoiding the previously produced memory cells (Option c).

Reason: To produce proper immune response for the same antigen memory cells develop & initiate a quick response if body is attacked again by the same antigen for the second time. But if the surface antigen changed, then memory cells unable to recognize it & thus failed to produce a quick immune response. Many viruses are able to change their surface antigen & thus avoid the detection of memory cells.

33) The answer will be antigens of the pathogen (Option e).

Reason: In order to recognize and combat pathogens by memory cells, which are more effective immune response antigens of the pathogens are introduced in the body. The immune system thus can safely learn to recognize antigens that are present in hostile invaders, produce antibodies & remember them for the future. Thus any future attack by the pathogens can generate quick immune response.

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