Question

the difference between essential and non - essential amino acids is that:
essential amino acids contain protein, and non - essential ones dont.
essential amino acids break down into sugar, while non - essential amino acids break down into lipids.
non - essential amino acids are produced by the body, while the body cannot produce essential amino acids on its own.
all of these choices are correct.

Explanation:

1. Analyze the first option: Both essential and non - essential amino acids are components of proteins (they are used to build proteins), so this statement is wrong.
2. Analyze the second option: Amino acids are the building blocks of proteins and do not break down into sugar or lipids in the way described. Their main metabolic fates are related to protein synthesis, energy production (through deamination and then entering metabolic pathways), or conversion to other molecules, but not breaking down into sugar or lipids as stated.
3. Analyze the third option: By definition, non - essential amino acids can be synthesized by the human body, while essential amino acids must be obtained from the diet because the body cannot produce them in sufficient amounts (or at all in some cases).
4. Analyze the fourth option: Since the first two options are incorrect, this option is also incorrect.

Answer:

C. non - essential amino acids are produced by the body, while the body cannot produce essential amino acids on its own.