<?xml version="1.0" encoding="utf-8"?><mads xmlns="http://www.loc.gov/mads/" xmlns:mods="http://www.loc.gov/mods/v3" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.loc.gov/mads/
mads.xsd"><authority><topic authority="http://AATesaurus.cultura.gencat.cat/aat/getty_en">amino acid</topic></authority><related type="narrower"><topic>glycine</topic></related><related type="narrower"><topic>cysteine</topic></related><related type="narrower"><topic>cystine</topic></related><related type="broader"><topic>acid</topic></related><variant type="other"><topic>acid, amino</topic></variant><variant type="other"><topic>amino acids</topic></variant> <note xml:lang="en"><![CDATA[ One of a class of organic acids marked by both an amine group and a carboxyl acid group. The 25 amino acids are the building blocks of protein and the end result of protein digestion. ]]></note></mads>