15. When glucuronic acid is formed in glucose, it is oxidized: aldehyde group amino group carboxyl group all -OH groups primary alcohol group

The correct answer is: all $-OH$ groups.<br /><br />When glucuronic acid is formed from glucose, it involves the oxidation of all the hydroxyl ($-OH$) groups in the molecule. This process is known as glucuronidation, where the hydroxyl groups of glucose are oxidized to carboxyl groups, resulting in the formation of glucuronic acid.