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What is the myelin sheath and what does it do?
- A. A group of nerve cells that perform a specific function.
- B. A fatty substance that insulates some nerve fibers.
- C. A fluid-filled cavity within the brain.
- D. The junction between two neurons.
Correct Answer: B
Rationale: The myelin sheath is a fatty substance that insulates some nerve fibers. It is made up of specialized cells that wrap around the axons of neurons, providing insulation and speeding up the transmission of nerve impulses. Choice A is incorrect as the myelin sheath is not a group of nerve cells but rather a substance that surrounds nerve fibers. Choice C is incorrect as the myelin sheath is not a fluid-filled cavity within the brain. Choice D is incorrect as the myelin sheath is not the junction between two neurons.
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What is the relationship between the Pauli exclusion principle and the structure of the atom?
- A. It defines the maximum number of electrons allowed in each energy level.
- B. It explains why oppositely charged particles attract each other.
- C. It describes the wave-particle duality of electrons.
- D. It determines the arrangement of protons and neutrons in the nucleus.
Correct Answer: A
Rationale: The Pauli exclusion principle states that no two electrons in an atom can have the same set of quantum numbers. This principle defines the maximum number of electrons allowed in each energy level, influencing the structure of the atom. Choice B is incorrect as it refers to the concept of electrostatic attraction, not directly related to the Pauli exclusion principle. Choice C is incorrect as it pertains to the wave-particle duality, a different aspect of quantum mechanics. Choice D is incorrect as it relates to the arrangement of protons and neutrons in the nucleus, not governed by the Pauli exclusion principle.
Which property of a substance refers to the force exerted on an object due to gravity?
- A. Mass
- B. Weight
- C. Density
- D. Volume
Correct Answer: B
Rationale: The correct answer is 'Weight.' Weight is the force exerted on an object due to gravity. Mass, on the other hand, refers to the amount of matter in an object. Density is the mass per unit volume of a substance, and volume is the amount of space occupied by an object. In this context, weight specifically relates to the gravitational force acting on an object, making it the most appropriate choice among the options provided.
What is the function of a cell wall?
- A. To provide structural support for the cell
- B. To transport substances in and out of the cell
- C. To synthesize proteins and lipids
- D. To store genetic material
Correct Answer: A
Rationale: The cell wall is a rigid layer that surrounds the cell membrane in plant cells, fungi, and some bacteria. Its main function is to provide structural support and protection for the cell, helping maintain the cell's shape and preventing it from bursting or collapsing. The cell wall also allows for the passage of water, ions, and other molecules in and out of the cell. Options B, C, and D are incorrect because those functions are typically carried out by other cellular structures. Option B is performed by the cell membrane, option C by ribosomes, and option D by the nucleus, which stores genetic material.
Which element is found in water and is crucial for biological functions like nerve impulses and muscle contraction?
- A. Sodium
- B. Potassium
- C. Calcium
- D. Magnesium
Correct Answer: A
Rationale: The correct answer is Sodium. Sodium is found in water and is crucial for biological functions like nerve impulses and muscle contraction. It plays a key role in maintaining electrolyte balance and transmitting nerve impulses, affecting both muscles and nerves. Potassium (Choice B), although essential for nerve function and muscle control, is not typically found in water. Calcium (Choice C) is important for bone health and muscle function, but it is not the element found in water. Magnesium (Choice D) is also essential for various biological functions but is not the element commonly found in water.
What is the waxy or oily substance produced by sebaceous glands that helps lubricate the skin and hair?
- A. Keratin
- B. Melanin
- C. Sebum
- D. Sweat
Correct Answer: C
Rationale: Sebum is the waxy or oily substance produced by sebaceous glands. It helps lubricate the skin and hair, keeping them moisturized and protected. Keratin is a protein that makes up hair, skin, and nails, providing structure and strength. Melanin is a pigment that gives color to the skin, hair, and eyes, providing protection against UV radiation. Sweat is a watery fluid produced by sweat glands to help regulate body temperature by cooling the body through evaporation.