Which of the following explains why there are so many differences in the properties of peptides and proteins?
a) several amino acid sequences are possible for proteins and peptides
b) some proteins are enzymes while others are not
c) proteins and peptides include nitrogen
d) amino acids form proteins and peptides

How does the digestive system interact with the circulatory system? a. messages sent as electrical impulses from the digestive system are transported throughout the body by the circulatory system. b. nutrients taken in and broken down by the digestive system are carried to various parts of the body by the circulatory system. c. nutrients and gases are absorbed by organs in the circulatory system. then, they are transported to all parts of the body by organs in the digestive system. d. oxygen and carbon dioxide are exchanged by organs in the digestive system, and the gases are carried to the rest of the body by the circulatory system.