Ethnic differences in skin color are primarily caused by differences in the
quantity of melanin produced
quantity of hemoglobin in the blood
UV radiation exposure
number of keratinocytes
number of melanocytes
The Correct Answer is A
A. quantity of melanin produced: Ethnic variations in skin color are due to differences in the amount and type of melanin synthesized and distributed by melanocytes. While all humans have roughly the same number of melanocytes, the activity level of these cells determines pigment intensity.
B. quantity of hemoglobin in the blood: Hemoglobin contributes to skin tone by giving a reddish or pinkish hue, especially in lighter skin. However, it does not account for the baseline differences in ethnic skin color.
C. UV radiation exposure: Sun exposure can increase melanin production temporarily, leading to tanning. However, long-term ethnic differences are genetically determined rather than solely influenced by environmental UV exposure.
D. number of keratinocytes: Keratinocytes are the primary cells of the epidermis and act as recipients of melanin granules from melanocytes. Their number does not vary significantly among ethnic groups and does not explain differences in skin color.
E. number of melanocytes: The number of melanocytes is relatively consistent across all ethnicities. It is the rate of melanin synthesis and the type of melanin produced that create the observed differences in skin pigmentation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Electron transport chain/oxidative phosphorylation:This stage of cellular respiration produces the majority of ATP, typically about 26–34 molecules per glucose. It relies on the transfer of electrons through protein complexes and the use of a proton gradient to drive ATP synthase activity.
B. oxidation reactions:Oxidation reactions remove electrons from molecules, often transferring them to NAD⁺ or FAD. While essential for energy extraction, these reactions alone do not directly generate large amounts of ATP.
C. substrate-level phosphorylation:This mechanism occurs during glycolysis and the Krebs cycle, producing ATP directly from enzyme-mediated reactions. However, it only accounts for a small fraction of ATP yield, about 2 ATP in glycolysis and 2 in the Krebs cycle.
D. lactic acid production:Lactic acid is formed in anaerobic respiration when pyruvate is reduced to lactate. This process regenerates NAD⁺ for glycolysis but yields no additional ATP beyond the small amount produced in glycolysis itself.
Correct Answer is A
Explanation
A. elastic fibers:Elastic fibers are present in the skin, lungs, and blood vessel walls, providing resilience and the ability to stretch and recoil. In the skin, they maintain flexibility; in the lungs, they allow expansion and recoil during breathing; in blood vessels, they help accommodate pressure changes from blood flow.
B. reticular fibers:Reticular fibers form supportive networks in organs like the spleen, liver, and lymph nodes, but they are not a common feature of skin, lungs, or blood vessel walls.
C. simple squamous epithelium:Simple squamous epithelium is found lining blood vessels (endothelium) and alveoli in the lungs, but it is not present in the skin, so it is not a shared characteristic of all three tissues.
D. simple columnar epithelium:Simple columnar epithelium lines parts of the digestive tract and some glandular ducts but is absent from skin, lungs, and blood vessels, making it irrelevant as a shared feature.
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