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Which of the following substances is the determinant of an individual's skin color?

A.

Elastin

B.

Hemoglobin

C.

Melanin

D.

Keratin

Answer and Explanation

The Correct Answer is C

A. Elastin is a protein found in connective tissue that provides elasticity, allowing the skin and other tissues to return to their original shape after stretching. It does not influence skin color. 

B. Hemoglobin is the oxygen-carrying component of red blood cells. It gives the skin a reddish tint due to blood flow, but it is not the primary determinant of overall skin color. 

C. Melanin is the pigment produced by melanocytes in the skin. The type and amount of melanin determine the color of an individual's skin, with darker skin having more melanin. 

D. Keratin is a structural protein found in the skin, hair, and nails, providing strength and protection. While it contributes to the skin's texture and appearance, it does not determine skin color. 


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Related Questions

Correct Answer is C

Explanation

A. GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter in the central nervous system, meaning it generally reduces neuronal excitability and does not play a role in excitatory neuromuscular transmission.
B. Glycine is also an inhibitory neurotransmitter, mainly in the spinal cord, and works to prevent over-excitation of neurons, not directly involved in neuromuscular transmission.
C. Acetylcholine is the primary neurotransmitter responsible for neuromuscular transmission. It binds to receptors on muscle cells, causing depolarization and triggering muscle contraction, thus playing an excitatory role.
D. Serotonin primarily functions in the brain to regulate mood, appetite, and sleep but does not play a direct role in neuromuscular transmission.

Correct Answer is C

Explanation

A. As previously noted, the length of the thoracic cavity increases, not decreases, during the contraction of inspiratory muscles.

B. The diaphragm moves downward (not upward) when it contracts, allowing the lungs to expand.

C. The contraction of the diaphragm and external intercostals increases the diameter of the thoracic cavity, providing space for the lungs to expand and fill with air. This is the correct answer.

D. The chest cavity does not compress the lungs during inspiration; instead, it expands to accommodate the lungs as they fill with air.

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