Which of the following statements is true of essential amino acids?
a. Their recycling is different from that of nonessential amino acids.
b. These amino acids do not contain a side chain attached to the backbone.
c. Alanine and cysteine are examples of essential amino acids.
d. These amino acids cannot be synthesized by the body.
e. These amino acids are produced in excess within the body.
The Correct Answer and Explanation is:
The correct answer is:
d. These amino acids cannot be synthesized by the body.
Explanation:
Essential amino acids are amino acids that the human body cannot synthesize on its own and, therefore, must be obtained through the diet. These amino acids are necessary for various physiological functions, including protein synthesis, enzyme activity, and neurotransmitter production. Unlike nonessential amino acids, which can be synthesized by the body, essential amino acids must come from external sources.
Let’s go through each option for clarity:
a. Their recycling is different from that of nonessential amino acids.
- This statement is incorrect. Both essential and nonessential amino acids undergo a process of recycling within the body. They are broken down and their components are reused in various metabolic processes, but their ability to be synthesized or not is the key difference, not their recycling process.
b. These amino acids do not contain a side chain attached to the backbone.
- This statement is also incorrect. All amino acids, whether essential or nonessential, contain a side chain (also known as the R-group) attached to the central carbon atom in the amino acid backbone. It is the side chain that gives each amino acid its distinct properties.
c. Alanine and cysteine are examples of essential amino acids.
- This statement is false. Alanine and cysteine are nonessential amino acids, meaning the body can produce them. Essential amino acids include lysine, tryptophan, methionine, and others that cannot be synthesized by the body.
d. These amino acids cannot be synthesized by the body.
- This statement is correct. Essential amino acids must be consumed through food sources, as the body lacks the enzymes needed to synthesize them. Examples of essential amino acids include leucine, isoleucine, valine, and histidine.
e. These amino acids are produced in excess within the body.
- This is false. Since essential amino acids cannot be synthesized by the body, they are not produced in excess. The body must rely on dietary intake to meet its needs.
In summary, essential amino acids are those that the body cannot produce and must be obtained from dietary protein sources. They are crucial for maintaining proper bodily functions, and the inability to synthesize them necessitates an adequate intake through food.