Which of the following is not attached to the central carbon atom in an amino acida. a carboxyl functional groupb. an amino functional groupc. an oxygend. a side chain ("r group")

The correct answer is C. An oxygen

Explanation:

Amino acid is a compound which serves as the building block or proteins. They are the smallest and simplest unit of protein. They contain carbon, oxygen, hydrogen, and oxygen.  

Each amino acid has a central carbon atom which is designated as alpha carbon which is attached with a carbonyl functional group, an amino-functional group, a hydrogen atom, and a side chain(R group). So oxygen is not bound directly with the central carbon atom.

The R group is different in different amino acid. Glycine is the simplest amino acid and it has H in place of the R group.

this is math not biology xd