Nokea
Antibodies, crucial for immune defense, are produced by:
- A. Neutrophils
- B. Lymphocytes
- C. Monocytes
- D. Basophils
Correct Answer: B
Rationale: Antibodies are produced by a specific type of lymphocyte known as B cells. B cells are a critical component of the adaptive immune system and are responsible for producing antibodies in response to pathogens. Neutrophils, monocytes, and basophils are types of white blood cells that are part of the innate immune response and do not have the function of producing antibodies. Neutrophils are primarily involved in phagocytosis, monocytes differentiate into macrophages and dendritic cells for antigen presentation, while basophils are involved in allergic reactions and parasitic infections.
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Which type of bond involves the complete transfer of electrons between atoms?
- A. Covalent bond
- B. Ionic bond
- C. Metallic bond
- D. Hydrogen bond
Correct Answer: B
Rationale: The correct answer is B, Ionic bond. Ionic bond involves the complete transfer of electrons from one atom to another, resulting in the formation of cations and anions. This transfer leads to the creation of strong electrostatic attraction between the oppositely charged ions. Covalent bonds, on the other hand, involve the sharing of electrons between atoms to achieve stability. Metallic bonds are formed in metals, where a sea of delocalized electrons surrounds positively charged metal ions, contributing to the metal's properties. Hydrogen bonds are intermolecular forces that occur between a hydrogen atom and a highly electronegative atom like oxygen or nitrogen, not involving the complete transfer of electrons.
Which property of matter remains constant regardless of changes in gravity?
- A. Mass
- B. Weight
- C. Volume
- D. Density
Correct Answer: A
Rationale: Mass is a measure of the amount of matter in an object and remains constant regardless of changes in gravity. Weight, on the other hand, is the force of gravity acting on an object and can vary depending on the strength of gravity. Volume is the amount of space an object occupies, and density is the mass per unit volume of a substance, both of which can change with changes in gravity. Therefore, mass is the property that remains the same regardless of variations in gravitational force. Choice B, Weight, changes with gravity as it is a force dependent on gravity. Choices C and D, Volume and Density, can be affected by changes in gravity as they are related to the space an object occupies and the mass per unit volume, respectively.
Which law of motion states that for every action, there is an equal and opposite reaction?
- A. Newton's First Law
- B. Newton's Second Law
- C. Newton's Third Law
- D. Law of Universal Gravitation
Correct Answer: C
Rationale: The correct answer is Newton's Third Law of Motion. This law states that for every action, there is an equal and opposite reaction. It means that when one object exerts a force on a second object, the second object exerts an equal force in the opposite direction back on the first object. This fundamental law describes the relationship between the forces acting on two interacting objects. Newton's First Law (Choice A) is known as the law of inertia and states that an object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an external force. Newton's Second Law (Choice B) relates the force acting on an object to its mass and acceleration. The Law of Universal Gravitation (Choice D) describes the force of gravity between two objects with mass and the distance between them.
What happens when the diaphragm contracts?
- A. Air is expelled from the lungs.
- B. The lungs expand to allow air intake.
- C. The vocal cords vibrate to produce sound.
- D. The trachea narrows to control airflow.
Correct Answer: B
Rationale: When the diaphragm contracts, it moves downward, creating more space in the chest cavity. This expansion of the chest cavity causes the lungs to expand as well, allowing air to be drawn into the lungs during inhalation. Therefore, the correct answer is that the lungs expand to allow air intake when the diaphragm contracts. Choices A, C, and D are incorrect because when the diaphragm contracts, it does not expel air from the lungs, cause the vocal cords to vibrate, or narrow the trachea to control airflow.
Where are most of the body's immune cells located?
- A. Blood
- B. Brain
- C. Skin
- D. Large intestine
Correct Answer: A
Rationale: - The majority of the body's immune cells are located in the blood. Immune cells, such as white blood cells (leukocytes), circulate throughout the body via the bloodstream to detect and fight off infections and foreign invaders.
- While immune cells are also present in other parts of the body like the lymph nodes, spleen, and bone marrow, the blood serves as a primary conduit for immune cells to travel to different tissues and organs to carry out their functions.
- The brain (option B) is protected by the blood-brain barrier, which limits the entry of immune cells into the brain to prevent inflammation and damage.
- The skin (option C) contains immune cells like Langerhans cells that help protect against pathogens, but the largest concentration of immune cells is found in the blood.
- The large intestine (option D) also houses a significant amount of immune cells due to its role in interacting with the external environment through the gut-associated lymphoid tissue, but the primary location for most of the body's immune cells is the blood.