Click a tool to the left and then click on the big white box to use it.
Use the 'Place' tools to place the given elements and the Connect tool to bond them together.
To form a double bond, use the 'connect' tool twice. Double bonds are blue.
To unbond elements, use the 'disconnect' tool. It will decrement bond strength, so disconnecting a double bond will make is single, disconnecting a single bond removes it.
The provided N must be the amino terminus, otherwise it will not check your answer correctly.
'Correct' versions are forms at pH 7 from the table on page 75 of Lehninger Principles of Biochemistry.
If it grades you incorrectly, use the 'dump' tool and email the contents of the text box below to landon@cs.washington.edu.