Nursing Elites

1. Which of the following properties is NOT characteristic of a covalent bond?

• A. Sharing of electrons between atoms
• B. High melting and boiling points
• C. Low electrical conductivity in solid state
• D. Directional bonding

Correct answer: B

Rationale: Covalent bonds are formed by the sharing of electrons between atoms, leading to the formation of molecules with directional bonding. This means that the atoms are held together in a specific orientation. Covalent compounds generally exhibit low melting and boiling points compared to ionic compounds due to the weaker intermolecular forces present in covalent compounds. Furthermore, covalent compounds do not conduct electricity in the solid state because the electrons are localized between the atoms and are not free to move and carry charge. Hence, high melting and boiling points are not characteristic of covalent bonds. The correct answer is 'B' because high melting and boiling points are typically associated with ionic compounds due to their strong electrostatic interactions, while covalent compounds have lower melting and boiling points. Choices A, C, and D are all characteristics of covalent bonds, making them incorrect answers for this question.

2. What are the white blood cells responsible for coordinating the immune response called?

• A. Red blood cells
• B. Platelets
• C. Lymphocytes
• D. Neutrophils

Correct answer: C

Rationale: Lymphocytes, which include B cells, T cells, and natural killer cells, are responsible for coordinating the immune response. They play a crucial role in recognizing and fighting against pathogens and foreign substances in the body. Red blood cells are responsible for oxygen transport, platelets aid in blood clotting, and neutrophils are white blood cells primarily involved in combating infections. Therefore, the correct answer is C, lymphocytes, as they are specifically involved in coordinating immune responses.

3. What is the cycle of infection?

• A. Reservoir host, means of exit, means of transmission, means of entrance, susceptible host
• B. Entry point, transmission, replication, exit, susceptible host
• C. Susceptible host, replication, transmission, entry, exit
• D. Transmission, replication, entry, exit, susceptible host

Correct answer: A

Rationale: The correct answer is A: 'Reservoir host, means of exit, means of transmission, means of entrance, susceptible host.' This cycle of infection involves the pathogen starting in a reservoir host, exiting through a means, being transmitted to another host, entering the new host through a means, and ultimately infecting the susceptible host. Choices B, C, and D are incorrect because they do not follow the correct sequence of events in the cycle of infection.

4. Which term refers to the resistance of a liquid to flow?

• A. Density
• B. Viscosity
• C. Surface tension
• D. Boiling point

Correct answer: B

Rationale: Viscosity is the term that refers to the resistance of a liquid to flow. It is a measure of how thick or sticky a fluid is and determines how easily a liquid can flow. Density (A) is a measure of how much mass is contained in a given volume and is not related to the resistance of a liquid to flow. Surface tension (C) is the property of a liquid that allows it to resist an external force due to the cohesive nature of its molecules, but it is not directly related to the resistance of a liquid to flow. Boiling point (D) is the temperature at which a liquid changes to a vapor and is not a measure of the resistance of a liquid to flow.

5. Endotoxins are toxic substances released by:

• A. Viruses
• B. Bacteria (gram-positive)
• C. Bacteria (gram-negative)
• D. Parasites

Correct answer: C

Rationale: Endotoxins are toxic substances that are part of the outer membrane of the cell wall of gram-negative bacteria. These toxins are released when the bacteria are destroyed or during bacterial growth. Endotoxins can cause a variety of harmful effects in the host, including fever, inflammation, and septic shock. Viruses do not produce endotoxins; they are typically associated with producing viral proteins that can be toxic to host cells. Gram-positive bacteria produce exotoxins, which are different from endotoxins found in gram-negative bacteria. Parasites, though capable of causing diseases, are not typically associated with the production of endotoxins.

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