Nokea
Which macromolecule serves as the repository of genetic information in all living organisms?
- A. Ribonucleic acid (RNA)
- B. Deoxyribonucleic acid (DNA)
- C. Protein
- D. Carbohydrate
Correct Answer: B
Rationale: - DNA is the macromolecule that serves as the repository of genetic information in all living organisms. It carries the genetic instructions necessary for the growth, development, functioning, and reproduction of organisms.
- RNA (option A) is involved in various cellular processes, including protein synthesis, but DNA is the primary molecule responsible for storing genetic information.
- Proteins (option C) are essential for various cellular functions but do not serve as the primary repository of genetic information.
- Carbohydrates (option D) are important for energy storage and structural support but do not store genetic information.
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What is the term for a solution that contains less solute than the maximum amount it could dissolve at a specific temperature and pressure?
- A. Saturated solution
- B. Unsaturated solution
- C. Supersaturated solution
- D. Concentrated solution
Correct Answer: B
Rationale: An unsaturated solution is a solution that contains less solute than the maximum amount it could dissolve at a specific temperature and pressure. In an unsaturated solution, more solute can still be added and dissolved in the solvent. Choice A, a saturated solution, refers to a solution in which the maximum amount of solute has been dissolved at a specific temperature and pressure, leading to equilibrium. Choice C, a supersaturated solution, contains more solute than it can normally hold at a specific temperature and pressure, achieved through special conditions followed by rapid cooling or evaporation. Choice D, a concentrated solution, refers to a solution with a high amount of solute compared to the amount of solvent, regardless of reaching the saturation point.
How does urine flow through the urethra?
- A. Continuously
- B. Only when the bladder is completely full
- C. Under voluntary control of sphincter muscles
- D. A combination of B and C
Correct Answer: C
Rationale: Urine flows through the urethra under voluntary control of sphincter muscles. These muscles can be consciously contracted or relaxed to control the flow of urine from the bladder to the outside of the body. Choice A is incorrect as urine flow is not continuous but rather regulated. Choice B is incorrect because urine flow is not restricted to only when the bladder is completely full. Choice D is incorrect as it inaccurately combines the two incorrect statements of choices B and C.
Which nervous system controls the involuntary 'fight-or-flight' response?
- A. Sympathetic nervous system
- B. Parasympathetic nervous system
- C. Enteric nervous system
- D. Sensory nervous system
Correct Answer: A
Rationale: The correct answer is the sympathetic nervous system. The sympathetic nervous system is responsible for activating the body's response to stress or danger, leading to the 'fight-or-flight' response. It prepares the body for action by increasing heart rate, dilating pupils, and redirecting blood flow to muscles. Choice B, the parasympathetic nervous system, is responsible for the body's 'rest-and-digest' activities, which are opposite to the 'fight-or-flight' response. Choice C, the enteric nervous system, primarily regulates the gastrointestinal system and is not directly involved in the 'fight-or-flight' response. Choice D, the sensory nervous system, transmits sensory information from the body to the central nervous system and is not responsible for the physiological changes associated with the 'fight-or-flight' response.
What is the muscular tube that connects the mouth to the stomach?
- A. Pharynx
- B. Esophagus
- C. Trachea
- D. Larynx
Correct Answer: B
Rationale: The correct answer is B: Esophagus. The esophagus is indeed the muscular tube that connects the mouth to the stomach. Food is transported down the esophagus via peristalsis, a series of muscle contractions. The pharynx is the area behind the mouth and nasal cavity, the trachea connects the larynx to the bronchi in the lungs, and the larynx is the voice box located in the throat. Therefore, choices A, C, and D are incorrect in the context of the question.
What is the feedback mechanism in the endocrine system that helps maintain hormone balance?
- A. Positive feedback, where a hormone stimulates its own release
- B. Negative feedback, where a hormone suppresses its own release
- C. Cascade effect, where one hormone triggers the release of another
- D. Dual hormone system, where two hormones work together
Correct Answer: B
Rationale: In the endocrine system, negative feedback is the mechanism by which hormone levels are regulated. When hormone levels reach a certain threshold, they signal the body to stop producing more of that hormone, thus maintaining a balance. Negative feedback (option B) is the correct answer as it helps in preventing overproduction of hormones by suppressing their own release. Positive feedback (option A) would lead to an excessive production of hormones, disrupting the balance. The cascade effect (option C) involves one hormone triggering the release of another but does not directly regulate hormone levels. The dual hormone system (option D) refers to two hormones working together but does not specifically address the feedback mechanism for maintaining hormone balance.