Question 1

Which of the following mechanical factors is MOST responsible for preventing pathogen colonization on the skin?

Accepted Answer

The skin's dry, tightly packed cells and low nutrient availability.

Question 2

Low pH on the skin acts as a chemical defense by:

Accepted Answer

Discouraging pathogen colonization by creating an inhospitable environment.

Question 3

Which of the following is NOT a function of complement proteins in the immune response?

Accepted Answer

Directly neutralizing toxins by binding to them.

Question 4

A patient with a fever is advised to rest rather than exercise. Which biological defense mechanism explains this recommendation?

Accepted Answer

Fever diverts energy from physical activity to immune responses.

Question 5

Which mechanical factor is most important in protecting the respiratory tract from infection?

Accepted Answer

Cilia constantly sweep potential pathogens away.

Question 6

Which chemical factor found in sweat helps prevent pathogen colonization?

Accepted Answer

Salt accumulation, which creates a low water environment.

Question 7

Phagocytosis is best described as:

Accepted Answer

A variety of white blood cells binding and ingesting foreign material.

Question 8

Which of the following is a biological factor that helps prevent infection by limiting iron availability to pathogens?

Accepted Answer

Transferrin in human milk binds free iron.

Question 9

Which of the following is a multi-step process involving both chemical and biological defenses?

Accepted Answer

Complement proteins bind to antibodies, causing inflammation and attracting phagocytes.

Question 10

Which of the following best explains why lysozyme is more effective against Gram-positive bacteria than Gram-negative bacteria?

Accepted Answer

Gram-positive bacteria have a thicker peptidoglycan layer that is targeted by lysozyme.

Question 11

Which of the following is an example of a mechanical defense in the gastrointestinal tract?

Accepted Answer

Vomiting expels pathogens from the body.

Question 12

Which process is enhanced by complement proteins acting as opsonins?

Accepted Answer

Phagocytosis by white blood cells.

Question 13

A patient with a skin infection is found to have reduced salt accumulation on their skin. Which defense mechanism is compromised?

Accepted Answer

Chemical defense discouraging pathogen colonization.

Question 14

Which of the following is a direct result of complement protein activation?

Accepted Answer

Cytolysis, causing cells to lyse.

Question 15

Which of the following best describes the role of interferons in nonspecific host defenses?

Accepted Answer

They inhibit viral replication within host cells.

Question 16

Which of the following is a reason why fever is considered a beneficial biological defense?

Accepted Answer

It increases the rate at which immune cells respond to infection.

Question 17

Which of the following is a multi-step defense involving both mechanical and chemical factors?

Accepted Answer

Mucous membranes trap pathogens and lysozyme in saliva digests their cell walls.

Question 18

Which of the following best explains why transferrin in human milk is important for infant immunity?

Accepted Answer

It binds free iron, limiting its availability to pathogens.

Question 19

Which of the following is a plausible consequence if complement proteins fail to bind to antibodies?

Accepted Answer

Reduced inflammation and impaired phagocyte attraction.

Question 20

Which of the following equations best represents the process of cytolysis caused by complement proteins?

Accepted Answer

$$\mathrm{C5b} + \mathrm{C6} + \mathrm{C7} + \mathrm{C8} + \mathrm{C9} ightarrow 	ext{Membrane Attack Complex (MAC)} ightarrow 	ext{Cell Lysis}$$

Nonspecific Defenses of the Host: Innate Immunity Mechanisms

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