Defense & Immune System

Health-care workers are exposed to many different types of pathogenic and nonpathogenic microorganisms. Which body systems work together to protect the body from pathogens?

• Digestive and excretory
• Endocrine and reproductive
• Circulatory and immune
• Muscular and skeletal

The only characteristic shared by a virus and a living cell is that they both --

• store genetic information in nucleic acids
• are primitive prokaryotes without nuclei
• perform respiration to obtain energy
• have a cell membrane and cytoplasm

An electron microscope photograph of a virus is shown.
The projections on the surface of this virus allow the virus to — 

• engulf a host cell 
• attach to a host cell 
• control a host cell’s DNA 
• signal other viruses to infect a host cell 

Which cell does the human immunodeficiency virus (HIV) directly attack that impairs the functioning of the immune system?

• Helper T-cells
• Killer T-cells
• Memory B-cells
• Macrophages

Viruses, unlike bacteria, 

• cause diseases only in animals
• can be destroyed by antibiotics
• are eukaryotic, with a nucleus
• can reproduce only in living cells

The major destructive result of an infection from invading viruses such as the influenza virus is --

• release of viral toxins in the bloodstream.
• destruction of cells by viral enzymes
• destruction of cells by viral replication
• interfering with the cell’s life functions

Cold sores are caused by the herpes simplex virus type 1. A company that wants to develop antiviral drugs would ask a research immunologist to study — 

• the mechanism used by the virus to infect cells 
• how closely related the virus is to cold viruses 
• the metabolism of the virus 
• meiosis in the virus 

The steps involved in viral replication are shown on the diagrams.
Place the steps in the correct order by listing the letters in the proper sequence: 

• C D B A
• D C A B
• A B D C
• D C B A

The final step in the viral replication cycle (the lytic cycle) not shown in the diagrams is

• the release of viral toxins by the new viruses inside the host cell
• the destruction of the host cell by lysing the cell and releasing the new viruses
• the creation of new viruses through cell division 
• the interference of the cell’s life functions by the new viruses which cause cell death

Many plant-eating organisms, including humans and grazing animals, are unable to digest the cellulose that makes up plant cell walls.  Most plant-eaters have a symbiotic relationship with a microorganism that actually digest the cellulose releasing the nutrients for the herbivore’s use.
Which organism lives in many herbivore intestine and aids in the digestive process?

• The bacterium Escherichia coli
• The fungus Trichophyton rubrum
• The protozoan Entamoeba histolytica
• The algae Fucus vesiculosus