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What is the primary composition of the stratum corneum, the outermost layer of the epidermis?
- A. Keratinized dead cells
- B. Melanocytes
- C. Langerhans cells
- D. Merkel cells
Correct Answer: A
Rationale: The stratum corneum, the outermost layer of the epidermis, is primarily composed of keratinized dead cells. These cells are flattened, fully keratinized, and lack nuclei, serving a protective function for the skin. Melanocytes are responsible for producing melanin, providing skin pigmentation. Langerhans cells are involved in the immune response within the skin. Merkel cells are associated with sensory functions in the skin, particularly in touch sensations. Therefore, the correct answer is A as it accurately reflects the main constituent of the stratum corneum, which acts as a barrier against external factors.
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What happens during a physical change in matter?
- A. A new substance with different properties is formed
- B. The chemical composition of the substance changes
- C. The original substance can be recovered by physical means
- D. Energy is either released or absorbed
Correct Answer: C
Rationale: During a physical change in matter, the original substance undergoes a change in its physical state or appearance without any change in its chemical composition. This means that the original substance can be recovered by physical means, such as melting, freezing, boiling, or condensing. No new substance is formed (option A), the chemical composition remains the same (option B), and energy changes can occur but are not a defining characteristic of a physical change (option D). The ability to recover the original substance by physical means distinguishes physical changes from chemical changes.
When unpolarized light passes through a polarizing filter, the intensity of the transmitted light is:
- A. Completely absorbed
- B. Reduced by half
- C. Unaffected
- D. Doubled
Correct Answer: B
Rationale: When unpolarized light passes through a polarizing filter, the filter only allows light waves oscillating in a specific direction to pass through while blocking light waves oscillating in other directions. Since unpolarized light consists of light waves oscillating in all possible directions, when it passes through a polarizing filter, only half of the light waves (those oscillating in the direction allowed by the filter) are transmitted. As a result, the intensity of the transmitted light is reduced by half. Choice A is incorrect because the light is not completely absorbed; choice C is incorrect because the polarizing filter affects the transmitted light; and choice D is incorrect because the intensity does not double, but rather decreases by half due to the selective transmission of light waves in a specific direction by the polarizing filter.
The kidneys are bean-shaped organs responsible for filtering waste products from the blood. What is the main nitrogenous waste product the kidneys eliminate?
- A. Carbon dioxide
- B. Ammonia
- C. Urea
- D. Glucose
Correct Answer: C
Rationale: The correct answer is C, urea. Urea is the main nitrogenous waste product eliminated by the kidneys. It is produced in the liver from protein metabolism and excreted in urine. Carbon dioxide is eliminated through the lungs as a waste product of cellular respiration and not by the kidneys. Ammonia, a toxic waste product, is converted to urea in the liver before being excreted by the kidneys. Glucose is a sugar that is reabsorbed by the kidneys and not excreted as waste.
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.
The 'fight-or-flight' response is triggered by the hormone released from the:
- A. Thyroid gland
- B. Adrenal glands
- C. Pituitary gland
- D. Pancreas
Correct Answer: B
Rationale: The 'fight-or-flight' response is triggered by the release of adrenaline (epinephrine) and norepinephrine from the adrenal glands. These hormones prepare the body to either confront or flee from a perceived threat or stressor. The adrenal glands are crucial in initiating this rapid physiological response. Choices A, C, and D are incorrect because the thyroid gland primarily regulates metabolism and energy levels, the pituitary gland controls other endocrine glands but does not directly trigger the 'fight-or-flight' response, and the pancreas is responsible for regulating blood sugar levels through insulin and glucagon, not for triggering the 'fight-or-flight' response.