A chiral carbom atom is basically a carbon atom that is bonded to four different types of elements or group of atoms that form a molecule.
In the picture provided by the question we can see two chiral carbon atoms, the first one is attached to NH2, H, CH2 and COO-
The second chiral carbon atom is attached to NH2, H, COOH and CH2
As you can see all the bonded elements or molecules are different.
