Viruses are not placed in any of the three domains of life because they lack cells, organelles and their own metabolism.
Correct Answer
True
True. Viruses are acellular, have no metabolism of their own and can reproduce only by using a host cell, so they are not considered living organisms and fall outside the domain system.
Category: Virus Structure and Replication
Question 2
Bacteriophages enter bacteria by endocytosis, carrying their entire capsid into the cytoplasm.
Correct Answer
False
False. Bacteriophages inject their nucleic acid into the bacterium and leave the empty capsid outside the cell. Endocytosis of the whole virus is a way some plant and animal viruses enter cells.
Category: Virus Structure and Replication
Question 3
Nonenveloped viruses such as poliovirus generally survive harsh conditions, like those in the gut, better than enveloped viruses do.
Correct Answer
True
True. Without a fragile outer membrane, nonenveloped viruses resist changes in temperature and pH and some disinfectants, which lets viruses like poliovirus and hepatitis A survive the digestive tract.
Category: Virus Structure and Replication
Question 4
HIV leaves its host cell mainly by lysis, bursting the cell and releasing all new virions at once.
Correct Answer
False
False. HIV is released by budding, in which virions leave one at a time wrapped in host membrane without immediately killing the cell. Release by lysis is seen in viruses such as rhinovirus.
Category: Virus Structure and Replication
Question 5
A retrovirus inserts a DNA copy of its RNA genome into the chromosomes of the host cell.
Correct Answer
True
True. Retroviruses use reverse transcriptase to make DNA from their RNA genome, and that DNA is integrated into the host genome, where the cell's machinery then expresses viral genes.
Category: Virus Structure and Replication
Question 6
Antiviral drugs such as acyclovir permanently remove herpes viruses from the body.
Correct Answer
False
False. Acyclovir reduces the number and severity of herpes outbreaks, but the virus stays latent in nervous tissue for life. Most antiviral drugs control symptoms rather than cure the infection.
Category: Viral Disease Control
Question 7
A rabies vaccine given after a bite can prevent disease because the virus can take weeks to reach the nervous system.
Correct Answer
True
True. The delay between a bite and the virus reaching the nervous system can be two weeks or more, which gives a vaccine time to build immunity that stops the infection.
Category: Viral Disease Control
Question 8
Innate immunity can respond to a pathogen only after the body has been exposed to it through earlier infection or vaccination.
Correct Answer
False
False. Innate immunity does not depend on prior exposure; it responds nonspecifically to any pathogen right away. It is adaptive immunity that builds up after exposure and keeps a memory.
Category: Innate Immunity
Question 9
Saliva, tears and mucus contain an enzyme that breaks down bacterial cell walls.
Correct Answer
True
True. These secretions contain lysozyme, which digests the cell walls of many bacteria and so acts as a chemical barrier of innate immunity.
Category: Innate Immunity
Question 10
During inflammation, capillaries near the injury constrict and become less permeable, which keeps fluid out of the tissue.
Correct Answer
False
False. Chemical signals make the capillaries dilate and become more permeable, so fluid leaks into the tissue and causes the swelling, redness and heat of inflammation.
Category: Innate Immunity
Question 11
Natural killer cells are lymphocytes that belong to the innate immune system rather than the adaptive system.
Correct Answer
True
True. Natural killer cells are lymphocytes, but they do not need a specific antigen or prior exposure; they detect unhealthy cells, such as virus-infected or cancerous cells, by changes in their MHC class I molecules.
Category: Innate Immunity
Question 12
Complement proteins circulate in the blood in their active form, ready to attack any cell they contact.
Correct Answer
False
False. Complement proteins circulate in an inactive form and become activated in a cascade when they encounter a microbe or an antibody bound to a pathogen, which protects healthy body cells.
Category: Innate Immunity
Question 13
B cells complete their maturation in the bone marrow.
Correct Answer
True
True. Both B and T cells are made in red bone marrow, and B cells also mature there, while T cells move to the thymus to mature.
Category: Humoral Immunity and Memory
Question 14
A single B cell carries many different kinds of antigen receptor, each able to bind a different antigen.
Correct Answer
False
False. Each B cell carries only one kind of antigen receptor, so it can bind only one specific antigen. The huge variety of receptors across the whole B cell population is what covers so many pathogens.
Category: Humoral Immunity and Memory
Question 15
Booster vaccinations strengthen immunological memory by imitating repeated exposure to the same antigen.
Correct Answer
True
True. Each exposure to the antigen adds to the pool of memory B and T cells, so a booster produces a quicker and stronger response if the real pathogen is met later.
Category: Humoral Immunity and Memory
Question 16
Passive immunity lasts longer than active immunity because the antibodies arrive ready-made.
Correct Answer
False
False. Passive immunity protects immediately but is temporary, because the borrowed antibodies break down and no memory cells are formed. Active immunity, made by the body's own cells, can last years.
Category: Humoral Immunity and Memory
Question 17
In type 1 diabetes, an immune response destroys the insulin-producing cells of the pancreas.
Correct Answer
True
True. Type 1 diabetes is an autoimmune disease in which an inflammatory T cell response attacks the pancreatic cells that make insulin, so patients need regular insulin injections.
Category: Immune Disorders
Question 18
Allergies are delayed hypersensitivity reactions that reach their peak one to two days after exposure to the allergen.
Correct Answer
False
False. Allergies are immediate hypersensitivity reactions driven by antibodies and mast cells, appearing within minutes of exposure. Delayed hypersensitivity, such as a poison ivy rash, is cell mediated and peaks after one to two days.
Category: Immune Disorders
Question 19
Epinephrine is used to treat anaphylactic shock because it counters the sharp drop in blood pressure and the narrowing of the airways.
Correct Answer
True
True. Anaphylaxis can be fatal, and antihistamines alone are not enough. Epinephrine raises blood pressure and opens the airways, reversing the most dangerous effects.
Category: Immune Disorders
Question 20
Children with severe combined immunodeficiency (SCID) are born with working B and T cells but lack innate defenses.
Correct Answer
False
False. SCID is an inherited immunodeficiency in which children are born without functioning B or T cells, leaving them without adaptive immunity and highly vulnerable to infection.
Category: Immune Disorders