Answer
An amino acid has an alpha Carbon bonded to four different groups: a carboxylic group, an amine group, a hydrogen atom and an R group.
Amino acids links together to form a protein by condensation reaction.
Work Step by Step
In an amino acid, the alpha carbon is bonded to an amine group $NH_{2}$, a carboxylic group $COOH$, a hydrogen atom $H$ and an $R$ group /side chain. This R group/side chains differs in all amino acids, giving an amino acid its characteristic property.
Two amino acids link together side by side, $OH$ of carboxylic group and $H$ of amine group is removed to form a water molecule. This process is called condensation. The resulting structure is called a dipeptide and the bond formed is called a peptide bond $CONH$. Many amino acids link together in this way to form a protein molecule.
