Nokea
How do efferent fibers exit the spinal cord?
- A. Through the anterior aspect
- B. Through the dorsal aspect
- C. Through the ventral aspect
- D. Through the lateral aspect
Correct Answer: C
Rationale: Efferent fibers, which carry motor commands, exit the spinal cord through the ventral aspect, also known as the anterior aspect. The correct answer is C, 'Through the ventral aspect.' Efferent fibers exiting through the ventral aspect are responsible for carrying motor commands from the spinal cord to the muscles and glands. Choices A, B, and D are incorrect. Efferent fibers do not exit through the dorsal, lateral, or anterior aspects of the spinal cord.
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How does the Law of Conservation of Mass apply to this reaction: 2H₂ + O₂ → 2H₂O?
- A. Electrons are not lost.
- B. The hydrogen does not lose mass.
- C. New water molecules are formed.
- D. There is no decrease or increase in matter.
Correct Answer: D
Rationale: The Law of Conservation of Mass states that matter cannot be created or destroyed in a chemical reaction. In the given reaction, 2 moles of hydrogen combine with 1 mole of oxygen to form 2 moles of water. The total mass of the reactants (hydrogen and oxygen) is equal to the total mass of the products (water), meaning there is no decrease or increase in matter. The total mass of the system remains constant, demonstrating the conservation of mass. Choices A, B, and C are incorrect because the conservation of mass does not specifically relate to electrons, individual elements (like hydrogen), or the formation of new molecules; instead, it focuses on the overall mass of the system before and after the reaction.
What is the fatty substance that coats axons to insulate, protect, and speed up impulses?
- A. Myelin
- B. Dendrite
- C. Neuron
- D. Synapse
Correct Answer: A
Rationale: The correct answer is 'Myelin.' Myelin is a fatty substance that functions as an insulator for axons, providing protection and enhancing the speed of electrical impulses along neurons. This insulation is essential for ensuring efficient and rapid communication within the nervous system. Choices B, C, and D are incorrect. Dendrites are branched extensions of a neuron that receive signals, neurons are the basic building blocks of the nervous system that transmit information, and synapses are the junctions between neurons where communication occurs.
What do large intestines absorb?
- A. Water, sodium, and potassium ions
- B. Proteins and carbohydrates
- C. Water, vitamin K, and bile salts
- D. Vitamins A, D, E, K
Correct Answer: C
Rationale: The correct answer is C. The large intestine absorbs water, vitamin K, bile salts, sodium, and chloride ions. It helps in maintaining the body's water and electrolyte balance, and also plays a role in absorbing certain vitamins and nutrients such as vitamin K. Choices A, B, and D are incorrect because proteins, carbohydrates, vitamins A, D, E, and K are primarily absorbed in the small intestine, not the large intestine.
Which of the following is directly transcribed from DNA and represents the first step in protein synthesis?
- A. siRNA
- B. rRNA
- C. mRNA
- D. tRNA
Correct Answer: C
Rationale: mRNA (messenger RNA) is directly transcribed from DNA in the nucleus during the process of transcription. It serves as a template for protein synthesis during translation in the cytoplasm. mRNA carries genetic information from the DNA to the ribosomes, where it determines the sequence of amino acids in a protein. Thus, mRNA represents the first step in protein synthesis as it carries the code from the DNA to be translated into a protein. Choice A, siRNA (small interfering RNA), is involved in post-transcriptional gene silencing and does not play a role in protein synthesis. Choice B, rRNA (ribosomal RNA), is a component of the ribosome and plays a structural and functional role in protein synthesis but is not directly transcribed from DNA. Choice D, tRNA (transfer RNA), is responsible for bringing amino acids to the ribosome during protein synthesis but is not directly transcribed from DNA.
What is the structure of DNA?
- A. Single-stranded, linear
- B. Double-stranded, linear
- C. Double-stranded, helix
- D. Single-stranded, helix
Correct Answer: C
Rationale: The correct answer is C: Double-stranded, helix. DNA is structured as a double helix formed by two strands of nucleotides. The nucleotides are paired with complementary bases (A-T and C-G) in the center, held together by hydrogen bonds. This double-stranded helical structure is a fundamental characteristic of DNA and essential for its function in storing genetic information. Choices A, B, and D are incorrect because DNA is not single-stranded; it consists of two strands that run antiparallel to each other and are connected via hydrogen bonds. Additionally, DNA does not have a linear structure but rather a helical one, providing stability and protection to the genetic information it carries.