Chapter 15, Problem 1Q

Summary Introduction

To review:

The classification of arginine as an essential amino acid in young animals.

Introduction:

Amino acids are amino-carboxylgroups containing biomolecules that act as building blocks for proteins. Different amino acids combine with each other through peptide bonds to form proteins. There are approximately 20amino acids known thatform various proteins. They are broadly categorized into two, essential (EAA) and nonessential amino acids (NEAA). EAA can be defined as the amino acids that cannot be synthesized within the body and are require to be absorbed through one’s diet, while NEAA are easily synthesizedin the body.

Explanation of Solution

Arginine is known to benon-essential amino acids in adult animals; this is because it is formed through the urea cycle present in the body. This cycle is not fully functional in young animals. This suggests that the formation of arginine with the help of this cycle within the body is hindered. This makes the amino acid an essential amino acid in young animals. In adults, the formation takes place in the following manner:

In the absence of urea cycle, it become difficult for young animals to synthesize arginine. This results in making it an essential dietary amino acid. Hence, this amino acid acts as an essential amino acid only in young animals. As soon as the animalgrows and the urea cycle begins, dietary intake of the amino acid is no longer required.

Conclusion

Therefore, it can be concluded that the lack of functionality of the urea cycle is the cause for making arginine an essential amino acid in infants. As soon as the cycle begins, with the growth of the organism, the amino acid is no longer an essential amino acid.