Nokea
Which structure allows for the selective passage of materials into and out of the cell?
- A. DNA
- B. Protein
- C. Carbohydrate
- D. Phospholipid bilayer
Correct Answer: D
Rationale: The phospholipid bilayer is a crucial component of the cell membrane, surrounding the cell and regulating the passage of materials into and out of the cell. Its structure enables it to be selectively permeable, controlling which substances can pass through. DNA, proteins, and carbohydrates are essential molecules in the cell but do not directly govern the passage of materials like the phospholipid bilayer does. Therefore, the correct answer is the phospholipid bilayer.
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Which term describes a substance's ability to undergo a change that transforms it into a different substance?
- A. Density
- B. Mass
- C. Reactivity
- D. Volume
Correct Answer: C
Rationale: Reactivity refers to a substance's ability to undergo a change that transforms it into a different substance through a chemical reaction. In this context, reactivity specifically refers to the chemical behavior of a substance. Density, mass, and volume are physical properties of a substance and do not describe its ability to undergo a chemical change. Density is the mass per unit volume, mass is the amount of matter in an object, and volume is the amount of space occupied by an object. Therefore, reactivity is the most appropriate term to describe a substance's ability to undergo a transformation into a different substance.
What are the moon-shaped white structures at the base of fingernails called?
- A. Lunulae
- B. Cuticle
- C. Hyponychium
- D. Matrix
Correct Answer: A
Rationale: The correct answer is A: Lunulae. The moon-shaped white structures at the base of fingernails are known as lunulae. They are most prominent on the thumb and are situated at the base of the nail matrix. The lunula is the visible part of the nail matrix, which is responsible for generating new nail cells. Choice B, Cuticle, is incorrect as it refers to the thin layer of skin at the base of the nail plate. Choice C, Hyponychium, is incorrect as it is the skin that lies beneath the free edge of the nail. Choice D, Matrix, is incorrect as it is the area where the nail is formed, located under the cuticle.
Which indicator is commonly used to distinguish between acidic and basic solutions?
- A. Methyl orange
- B. Phenolphthalein
- C. Universal indicator
- D. All of the above are common indicators.
Correct Answer: B
Rationale: Phenolphthalein is commonly used to differentiate between acidic and basic solutions. It changes color, turning pink in basic solutions and remaining colorless in acidic solutions due to a specific pH range. While methyl orange and universal indicator are also indicators used for pH testing, phenolphthalein is especially known for its distinctive color change in response to acidic and basic solutions, making it the correct choice. Methyl orange is typically used in titrations for a sharp color change at a specific pH, and the universal indicator is a mixture of indicators displaying a range of colors depending on the pH value, not specifically tailored to acidic and basic distinctions.
What is the difference between a sensory neuron and a motor neuron?
- A. Sensory neurons carry signals from sensory receptors towards the central nervous system, while motor neurons carry signals away from the central nervous system to muscles and glands.
- B. Sensory neurons control voluntary muscles, while motor neurons control involuntary muscles.
- C. Sensory neurons are located in the peripheral nervous system, while motor neurons are located in the central nervous system.
- D. Sensory neurons detect light, while motor neurons detect sound.
Correct Answer: A
Rationale: Sensory neurons are responsible for carrying signals from sensory receptors towards the central nervous system (brain and spinal cord), allowing the brain to receive information about the external environment. On the other hand, motor neurons carry signals away from the central nervous system to muscles and glands, enabling the brain to control voluntary and involuntary movements. Choice B is incorrect because sensory neurons do not control muscles, and motor neurons control both voluntary and involuntary muscles. Choice C is incorrect as sensory neurons are located in the peripheral nervous system, while motor neurons are located in the central nervous system. Choice D is incorrect because sensory neurons detect various stimuli such as touch, taste, smell, and sound, while motor neurons are not involved in detecting sensory stimuli.
What element is responsible for the red color of blood?
- A. Magnesium
- B. Iron
- C. Copper
- D. Zinc
Correct Answer: B
Rationale: The correct answer is B: Iron. Hemoglobin, the protein responsible for carrying oxygen in red blood cells, contains iron in its heme group, contributing to the blood's characteristic red color. Magnesium (choice A), copper (choice C), and zinc (choice D) are not responsible for the red color of blood. Magnesium is an essential mineral involved in various physiological processes, copper is a trace element important for enzyme function, and zinc is a micronutrient essential for multiple cellular functions but not related to the red color of blood.