which of the following statements about the ubiquitination of proteins are true? ubiquitin is a relatively small protein that is widely expressed in eukaryotic cells. it is covalently attached to target proteins in an atp-dependent reaction. a carboxyl group of ubiquitin forms amide bonds with free amines found on the target protein. target selection is determined by ubiquitin-protein ligases. view available hint(s)for part a which of the following statements about the ubiquitination of proteins are true? ubiquitin is a relatively small protein that is widely expressed in eukaryotic cells. it is covalently attached to target proteins in an atp-dependent reaction. a carboxyl group of ubiquitin forms amide bonds with free amines found on the target protein. target selection is determined by ubiquitin-protein ligases. only statements 2, 3, and 4 are correct. only statements 1, 2, and 4 are correct. only statements 1, 2, and 3 are correct. all of the listed statements are correct.