Question

The amino acids that must be consumed in the diet are called essential. Nonessential amino acids a. can be produced by the body. b. are only needed occasionally. c. are stored in the body until needed. d. can be taken in by supplements.

Short answer

Nonessential amino acids can be produced by the body. Therefore, the correct answer is option (a).

Step-by-step solution

Understanding Essential and Nonessential Amino Acids

Amino acids are the building blocks of proteins. They are classified into two groups based on whether the body can produce them or not: essential and nonessential amino acids. Essential amino acids are those that our body cannot produce and must be obtained through our diet. Nonessential amino acids, on the other hand, can be synthesized by the body and does not need to be consumed through the diet. Now, let's analyze each option and select the correct one.

Option (a): can be produced by the body

This option aligns with our understanding of nonessential amino acids. They can be synthesized by the body, which means they do not have to be obtained through the diet.

Option (b): are only needed occasionally

This option is incorrect. Nonessential amino acids are still important for the normal functioning of the body; they can be produced by the body and are not dependent on a dietary source.

Option (c): are stored in the body until needed

This option is also incorrect. Amino acids do not have a specific storage form in the body. They can be broken down into other compounds or used to synthesize proteins as needed, but they are not "stored" for future use like some other nutrients.

Option (d): can be taken in by supplements

While it is true that amino acids, both essential and nonessential, can be consumed through supplements, this option does not specifically describe the unique characteristic of nonessential amino acids. So, this option is not the best choice. Based on the analysis of the given options, the correct answer is: Nonessential amino acids: a. can be produced by the body.

Key concepts

Essential Amino Acids

Amino acids are the fundamental components of proteins, quintessential for life. Essential amino acids are a specific group that our bodies cannot synthesize; thus, they must be supplied through our diet. There are nine essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

These compounds are crucial for various metabolic processes, such as tissue repair and nutrient absorption. A lack of any essential amino acid can lead to negative health effects, ranging from growth delays to compromised immune function. Foods such as meats, dairy, eggs, and certain plant-based sources like quinoa and soy are rich in essential amino acids.

Protein Synthesis

At the cellular level, protein synthesis is an elegant and complex process of building proteins from amino acids. It consists of two main stages: transcription and translation. During transcription, the DNA sequence in a gene is copied into messenger RNA (mRNA). Translation follows with the mRNA decoding on ribosomes to assemble amino acids into polypeptide chains that form proteins.

Each amino acid is brought to the ribosome by a specific molecule known as transfer RNA (tRNA). The order in which amino acids are assembled is dictated by the nucleotide sequence of the mRNA. Once the polypeptide chain is complete, it undergoes various modifications to become a functioning protein. This process is significant not only for growth and repair but also for enzymatic activities and hormonal functions.

Amino Acid Classification

Amino acid classification is based largely on their necessity for the human diet and the body’s capacity to synthesize them. As we discussed with essential amino acids, which are diet-dependent, there are also nonessential amino acids that can be produced by the human body from other organic molecules.

Beyond the essential and nonessential categorizations, there are also conditionally essential amino acids. These are typically synthesized by the body; however, under certain conditions like illness or stress, additional amounts may be required from the diet. These include arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine. The understanding of amino acid classification is crucial for nutritional sciences, as it guides dietary recommendations and supplementation practices.