Question

#9
the human immunodeficiency virus (hiv)
often infects and destroys cd4 t cells.
these cd4 t cells are one of many kinds
of white blood cells that are an important
part of the immune system.
the most common danger related to the
destruction of cd4 t cells is -
a an increase in the risk of high blood
pressure
b an increase in the threat of diseases
caused by microorganisms and viruses
c a decrease in the flow of blood to vital
organs
d a decrease in the amount of oxygen
being transported to tissues

#10
viruses can be transmitted through air, water, food,
insect bites, and direct skin contact. once a virus
gains entry to the body, it invades a host cell in orde
to -
a deactivate the host cells defenses
b synthesize antibodies for defense
c metabolize host proteins and grow
d access cellular processes for replication

#11
which of these describes a difference between viruses
and cells?
a cells contain protein, and viruses contain only
carbohydrates.
b viruses have flagella, and cells have only cilia.
c cells reproduce independently, and viruses require
a host to reproduce.
d viruses have membranes made of proteins, and
cells have membranes made of nucleic acid.

#12
in the 1880s, louis pasteur developed a
method of weakening viruses. the
weakened viruses could be injected into
healthy individuals.
how is this method effective in fighting viral
diseases?
a the immune system develops antibodies in response to the weakened viruses.
b the weakened viruses attach to unaffected viruses in the host and interrupt the viral reproductive
cycle.
c the rate of genetic mutation in the host is decreased due to the introduction of weakened viruses.
d weakened viruses are unable to enter the host organism.

Explanation:

• Question #9: CD4 T cells are part of the immune system. When they are destroyed, the immune system is weakened. A weakened immune system means the body has less ability to fight off diseases caused by microorganisms and viruses.
• Question #10: Viruses are non - living and need a host cell. They invade host cells to use the cellular processes (like the host cell's machinery for making proteins, etc.) to replicate themselves.
• Question #11: Cells can reproduce independently (e.g., by mitosis in eukaryotic cells). Viruses are not cells; they lack the cellular machinery to reproduce on their own and require a host cell.
• Question #12: When weakened viruses are injected, the immune system recognizes them as foreign (antigens). The immune system then responds by producing antibodies. These antibodies can later recognize and fight the actual, stronger form of the virus if the person is exposed to it.

Answer:

• #9: B. an increase in the threat of diseases caused by microorganisms and viruses
• #10: D. access cellular processes for replication
• #11: C. Cells reproduce independently, and viruses require a host to reproduce
• #12: A. The immune system develops antibodies in response to the weakened viruses