Human skin color is determined by the interaction of melanin, carotene and hemoglobin. Storage of water, fat, glucose and vitamin D is also a function of the integumentary system, according to the AAD.
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DAT Test Study Guide with Practice Questions. There are four sections on the DAT, all of them multiple choice. They are: Natural Sciences, Perceptual Ability (commonly referred to as PAT), Reading Comprehension, and Quantitative Reasoning. It takes five hours to complete the exam. (Applicants may take an optional 15 minute break during the test if they so choose.) Natural Sciences contains 40 biology questions, 30 general chemistry questions, and 30 organic chemistry questions, for a total of 100, with a time limit of 90 minutes.