来自《耶鲁大学开放课程：生物医学工程探索 第7集 第7集》

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  Hormones can be proteins,
  激素可以是蛋白
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  endocrine hormones can be proteins,
  内分泌激素可以是蛋白
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  meaning they're large molecules
  这意味着激素是大分子
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  that are usually fairly water soluble,
  并且通常是水溶性的
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  or they can be steroids.
  激素也可以是类固醇
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  Steroids are small molecules - much smaller than proteins -
  类固醇是小分子物质 比蛋白质小得多
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  smaller molecules that tend to be hydrophobic
  这类小分子是非水溶性的
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  or lipid soluble.
  或者说是脂溶性的
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  Example, protein hormones are insulin
  例如 我们以前讲过的胰岛素
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  which we've talked about before and glucagon,
  还有胰高血糖素都是蛋白质激素
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  and growth hormone which we haven't talked about
  生长激素也是 尽管我们还没有讲过它
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  but that's very important
  但它在人的青春期阶段