Nokea
Which of the following properties of water explains its solvent abilities for certain substances?
- A. High specific heat
- B. Polarity
- C. Volume
- D. High surface tension
Correct Answer: B
Rationale: The correct answer is B: Polarity. Water's polarity, resulting from its unequal sharing of electrons and the formation of hydrogen bonds, makes it an excellent solvent. The polar nature of water allows it to interact with and dissolve substances that have charges or partial charges, aiding in their breakdown at a molecular level. Choices A, C, and D are not directly associated with water's solvent capabilities. High specific heat (Choice A) refers to water's ability to resist temperature changes, volume (Choice C) is the amount of space occupied by water, and high surface tension (Choice D) pertains to water's cohesive properties.
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Which of the following actions contributes to the repolarization of a neuron?
- A. Inhibition of sodium and potassium pumps to stop all ion movement into the neuron.
- B. Opening of potassium channels to allow potassium to leave the neuron.
- C. Closing of both sodium and potassium channels to restrict the movement of ions into and out of the neuron.
- D. Opening of sodium channels to allow sodium to enter the neuron.
Correct Answer: B
Rationale: Repolarization is the phase where the neuron returns to its resting membrane potential after depolarization. Opening of potassium channels is crucial during repolarization as it enables potassium ions to move out of the neuron, helping restore the negative charge inside the cell. This outward movement of positively charged potassium ions is necessary for repolarization, countering the sodium influx that occurred during depolarization. Therefore, the correct answer is the opening of potassium channels to allow potassium to leave the neuron.
Which substance protects the body from ultraviolet rays?
- A. Keratin
- B. Sebum
- C. Perspiration
- D. Melanin
Correct Answer: D
Rationale: Melanin is the pigment responsible for skin color and serves as a natural defense against ultraviolet (UV) rays. When the skin is exposed to UV rays, melanin production increases to absorb and dissipate the radiation, acting as a protective mechanism. This helps prevent DNA damage, reducing the risk of skin cancer and other UV-induced skin issues. Therefore, melanin is the substance that effectively shields the body from the harmful effects of UV radiation.
In a study, two processes, process A and process B, were found to be correlated. Which of the following statements is true regarding these processes?
- A. The study cannot determine if processes A and B have a negative relationship.
- B. The study suggests that process A causes process B.
- C. The study cannot determine if processes A and B have a positive relationship.
- D. The study does not establish a causal relationship between process A and process B.
Correct Answer: D
Rationale: When two processes are correlated, it means changes in one process are linked to changes in the other. However, correlation does not imply causation. Therefore, the study does not establish a causal relationship between process A and process B solely based on correlation. Correlation does not provide information on the direction or cause of the relationship between the processes. It only indicates that the processes vary together in a predictable manner. Hence, option D is correct as the study cannot infer causation from correlation alone.
From which region of the intestine does the vermiform appendix extend, known as which of the following?
- A. Ischium
- B. Cecum
- C. Rectum
- D. Jejunum
Correct Answer: B
Rationale: The correct answer is B, Cecum. The vermiform appendix, a small tube-like structure, extends from the cecum, located in the lower right quadrant of the abdomen. Knowing the anatomical relationships among different intestinal parts is essential for identifying the appendix's origin.
Which of the following describes one difference between skeletal and cardiac muscles?
- A. Cardiac muscles are involuntary, whereas skeletal muscles are voluntary
- B. Skeletal muscles are not autorhythmic, whereas cardiac muscles are
- C. Skeletal muscles are found in the limbs, whereas cardiac muscles are found in the heart
- D. Skeletal muscles are not autorhythmic
Correct Answer: A
Rationale: The correct answer is A because cardiac muscles are involuntary, meaning they are not under conscious control, while skeletal muscles are voluntary, allowing conscious control over their movement. Option B is incorrect as skeletal muscles are not autorhythmic, unlike cardiac muscles. Option C is inaccurate as skeletal muscles are primarily found in the limbs, while cardiac muscles are predominantly located in the heart. Option D is false as skeletal muscles are not autorhythmic; instead, cardiac muscles possess autorhythmicity due to their ability to generate and conduct electrical impulses independently.