Most Animals Digest Dietary Proteins into Their Constituent Amino Acids

Multiple Choice

Most animals digest dietary proteins into their constituent amino acids and then synthesize new proteins because

A) macromolecules like proteins cannot be readily transported through plasma membranes.
B) protein structure and function are highly species-specific.
C) foreign proteins are considered invaders and are attacked by the immune system.
D) All of the above
E) None of the above