Answer:
a. The alpha-carbon
Explanation:
An amino acid is an organic molecule that contains a carboxyl (COOH) and a amino (NH2) group. It has a central carbon called as alpha carbon.
The carboxyl and amino groups are attached to the the alpha carbon. Apart from them, a side chain denoted by "R" is also covalently attached to it. Side chain varies in each amino acid and it imparts the unique properties to the particular amino acid.
The order of levels of organization from smallest to largest is Specialized Cells, Cardiac Muscle, Heart.
<span>Scientist rejected Wegener's hypothesis of continental drift at first because he did not have enough evidence to support his theory. He failed to provide a suitable mechanism that could cause the continents to move. </span>
