This is important because this molecule here, deoxyribose, is not the same upside down as it is - it's not symmetrical upside down and right side up, it's different because the 5' carbon's either pointed up or pointed down.

这很重要,因为对脱氧核糖来说,不都是像这样自上而下的,不是对称的自上向下或全部向上的,长链不同是由于,5'碳向上或者向下的指向不同

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