A polymer is just a large molecule that's made up of repeated units.

聚合物就是由,重复单位构成的大分子

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Cross-linked is not the right word-- that is chemically bonded with repeat units to make large molecules so that when you have a bunch of large molecules together they have certain physical properties like the solid property of the plastic that you're sitting on.

交联这个词不确切,应该是由化学键连接的,重复单位构成大分子,当许多分子聚合在一起后,它们就会具有某种物理特性,就像你们正坐着的,塑料一样,具有固体特性

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So the repeating unit in DNA is this structure here, a nucleotide, which has three different regions.

NA的重复单位就是,核苷酸,它有三个不同的区域

耶鲁公开课 - 生物医学工程探索课程节选