Which of the following substances protects the skin from ultraviolet radiation?
Melanin.
Perspiration.
Sebum.
Keratin.
The Correct Answer is A
Melanin is a pigment produced by cells called melanocytes in the skin.
It protects the skin from ultraviolet (UV) radiation by absorbing and dissipating over 99.9% of absorbed UV radiation.
This helps to prevent DNA damage and other adverse effects of UV radiation on the skin.
Choice B. Perspiration is not correct because it is a fluid produced by sweat glands in the skin that helps to regulate body temperature, but it does not protect the skin from UV radiation.
Choice C. Sebum is not correct because it is an oily substance produced by sebaceous glands in the skin that helps to lubricate and protect the skin, but it does not protect the skin from UV radiation.
Choice D. Keratin is not correct because it is a fibrous protein that provides strength and durability to the skin, hair and nails, but it does not protect the skin from UV radiation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A possible modification could be: “Parasitic worm infestation can have both damaging and beneficial effects on the host.
While it can cause harm, it has also been found to reduce the severity of certain autoimmune disorders.”
Choice A. Worm infestation prevents the body from immune malfunction is not correct because it overstates the findings and implies that worm infestation completely prevents immune malfunction, which is not supported by the evidence.
Choice C. Worm infestations exacerbate the body’s immune reactions is not correct because it contradicts the new findings that worm infestation can relieve the effects of certain autoimmune disorders.
Choice D. Lack of worm infestations is the cause of some autoimmune disorders is not correct because it overstates the findings and implies a causal relationship between lack of worm infestations and autoimmune disorders, which is not supported by the evidence.
Correct Answer is B
Explanation
The correct answer is choice B. 3’ TCGATCGCA 5’.
In DNA, the nitrogenous bases adenine (A) and thymine (T) pair together, while cytosine © and guanine (G) pair together.
Therefore, the complementary strand of the given DNA sequence “5’ AGCTAGCGT 3’” would have the nitrogenous bases T, C, G, A, T, C, G, C and A in that order.
Additionally, the 5’ to 3’ direction of the complementary strand is opposite to that of the given strand.
Choice A. 3’ AGCTAGCGT 5’ is not correct because it is not complementary to the given strand.
Choice C. 5’ UCGAUCGCA 3’ is not correct because it contains uracil (U), which is a nitrogenous base found in RNA, not DNA.
Choice D. 3’ TCGUTCGCU 3’ is not correct because it also contains uracil (U), which is a nitrogenous base found in RNA, not DNA.
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