What is an example of a structural plant defense?
tea tree oil produced by the melaleuca tree.
ricin produced by the castor bean plant.
thorns produced by the acacia tree.

Amino acids contain the elements carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. of the 20 amino acids found in humans, 11 are called "nonessential" because they can be manufactured by the body when needed. which elements in these 11 amino acids are commonly obtained from the metabolism of sugar molecules?