Nokea
Which hormone, produced by the pancreas, is involved in the regulation of blood sugar levels by inhibiting the release of insulin and promoting the release of glucose into the bloodstream?
- A. Insulin
- B. Glucagon
- C. Cortisol
- D. Somatostatin
Correct Answer: D
Rationale: The correct answer is D, Somatostatin. Somatostatin is a hormone produced by the pancreas that plays a crucial role in regulating blood sugar levels by inhibiting the release of insulin and promoting the release of glucose into the bloodstream. It acts as a counterbalance to insulin, preventing excess insulin secretion and ensuring the availability of glucose when needed. Therefore, somatostatin helps maintain blood sugar balance in the body. Choices A, B, and C are incorrect. Insulin is responsible for lowering blood sugar levels, while glucagon and cortisol have roles that differ from the functions described in the question.
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Which neurotransmitter is responsible for stimulating muscle contraction?
- A. Dopamine
- B. Acetylcholine
- C. Serotonin
- D. Norepinephrine
Correct Answer: B
Rationale: Acetylcholine is the neurotransmitter responsible for stimulating muscle contraction at the neuromuscular junction. When an action potential reaches the end of a motor neuron, acetylcholine is released into the synaptic cleft and binds to receptors on the muscle cell membrane, leading to muscle contraction. Dopamine, serotonin, and norepinephrine are neurotransmitters that have different functions in the nervous system and are not directly involved in stimulating muscle contraction. Dopamine is involved in reward and pleasure pathways, serotonin regulates mood and behavior, and norepinephrine is involved in the 'fight or flight' response.
When ethanol (Câ‚‚Hâ‚…OH) reacts with sodium metal (Na), what is the product?
- A. Ethene (Câ‚‚Hâ‚„)
- B. Sodium ethoxide (Câ‚‚Hâ‚…ONa)
- C. Ethane (C₂H₆)
- D. Sodium acetate (CH₃COONa)
Correct Answer: B
Rationale: When ethanol (C₂H₅OH) reacts with sodium metal (Na), the product formed is Sodium ethoxide (C₂H₅ONa). This reaction is a classic example of a metal displacing hydrogen in an alcohol to form an alkoxide. In this specific case, sodium replaces the hydrogen in ethanol, resulting in the formation of sodium ethoxide. Choice A, Ethene (C₂H₄), is incorrect as it is a different compound formed from the dehydration of ethanol, not its reaction with sodium. Choice C, Ethane (C₂H₆), is incorrect as it is a saturated hydrocarbon, not the product of the reaction of ethanol with sodium metal. Choice D, Sodium acetate (CH₃COONa), is incorrect as it involves acetic acid, not ethanol, reacting with sodium to form the salt sodium acetate.
In the process of cellular respiration, glucose is broken down to produce energy. What is the main waste product released?
- A. Water
- B. Carbon dioxide
- C. Oxygen
- D. Protein
Correct Answer: B
Rationale: During cellular respiration, glucose undergoes a series of reactions in the presence of oxygen to produce energy in the form of ATP. The main waste product released in this process is carbon dioxide, which is eliminated from the body through exhalation. While water is also produced as a byproduct of cellular respiration, carbon dioxide is considered the primary waste product. Oxygen is not a waste product but is actually consumed during cellular respiration to aid in breaking down glucose. Protein is essential for various cellular functions but is not a waste product of cellular respiration; instead, proteins are broken down into amino acids for cellular processes.
What are the differences between RNA and DNA?
- A. Both have the same structure and function.
- B. RNA is single-stranded, while DNA is double-stranded.
- C. RNA contains ribose sugar, while DNA contains deoxyribose sugar.
- D. RNA has adenine and guanine, while DNA has thymine and cytosine.
Correct Answer: B
Rationale: A) This statement is incorrect. RNA and DNA have different structures and functions. RNA is involved in protein synthesis and other cellular processes, while DNA stores genetic information. B) This statement is correct. RNA is typically single-stranded, while DNA is double-stranded, forming a double helix structure. C) This statement is correct. RNA contains ribose sugar in its backbone, while DNA contains deoxyribose sugar. D) This statement is incorrect. RNA contains adenine, guanine, cytosine, and uracil, while DNA contains adenine, guanine, cytosine, and thymine. Choice B is the correct answer as it accurately describes one of the key differences between RNA and DNA, emphasizing their structural disparity in terms of single-strandedness for RNA and double-strandedness for DNA. Choices A, C, and D contain inaccuracies regarding the structural and compositional distinctions between RNA and DNA, making them incorrect choices.
What is the outermost layer of the dermis, rich in collagen and elastin fibers that provide elasticity to the skin?
- A. Papillary layer
- B. Reticular layer
- C. Stratum basale
- D. Stratum corneum
Correct Answer: B
Rationale: The correct answer is the reticular layer. This layer is the outermost layer of the dermis that contains abundant collagen and elastin fibers, providing elasticity to the skin. The papillary layer is located beneath the epidermis and is responsible for supplying nutrients to the epidermis, not the outermost layer. The stratum basale is the deepest layer of the epidermis where new skin cells are produced, not part of the dermis. The stratum corneum is the outermost layer of the epidermis composed of dead skin cells, not a layer of the dermis.