Dietary proteins:
1. consist of all 20 amino acids required in the human body.
2. are nutritionally identical, because all are broken down into their constituent amino acids in the digestive system.
3. are considered “complete” only if they contain all of the non-essential amino acids required by humans.
4. are considered “complete” only if they contain all of the essential amino acids required by humans.
5. can be obtained from animal sources, but not plant sources.