Which one of the following is not an essential amino acid?

The human body requires 20 different amino acids to function properly, which are the fundamental building blocks of protein. For many, determining which one of the following is not an essential amino acid is the first step toward understanding the complexities of human nutrition and metabolism.

Quick Summary

This guide explains the difference between essential and non-essential amino acids, clarifying which ones the body can produce and which must be obtained from the diet. It provides a comprehensive list and comparison.

Key Points

• Essential vs. Non-Essential: The main difference is whether the body can synthesize the amino acid.

• Body's Synthesis: Non-essential amino acids like alanine are produced internally.

• Dietary Requirement: Essential amino acids must be consumed through diet.

• Conditionally Essential: Some amino acids become essential through diet during stress or illness.

• Complete Proteins: Foods with all nine essential amino acids are complete proteins.

• Incomplete Proteins: Most plant proteins lack one or more essential amino acids, but combining sources can provide all essential amino acids.

The Difference Between Essential and Non-Essential Amino Acids

Amino acids are organic compounds that combine to form proteins, which are vital for building and repairing tissues, producing enzymes and hormones, and performing many other functions in the body. The 20 amino acids used by the human body are classified as either essential or non-essential based on whether the body can synthesize them.

Essential Amino Acids

Essential amino acids cannot be produced by the body and must be acquired through diet. There are nine essential amino acids:

• Histidine
• Isoleucine
• Leucine
• Lysine
• Methionine
• Phenylalanine
• Threonine
• Tryptophan
• Valine

These are crucial for various bodily processes, including tissue repair and immune function.

Non-Essential Amino Acids

Non-essential amino acids are those the body can synthesize, so dietary intake is not strictly necessary. The body produces these from other amino acids or metabolic intermediates. There are eleven non-essential amino acids:

• Alanine
• Arginine (often conditionally essential)
• Asparagine
• Aspartic Acid
• Cysteine (often conditionally essential)
• Glutamic Acid
• Glutamine (often conditionally essential)
• Glycine (often conditionally essential)
• Proline (often conditionally essential)
• Serine (often conditionally essential)
• Tyrosine (often conditionally essential)

Conditionally Essential Amino Acids

Some non-essential amino acids are termed "conditionally essential". While the body can usually make them, their production may not meet increased demands during illness, stress, or growth spurts, making dietary sources temporarily necessary. Examples include arginine and glutamine.

Identifying a Non-Essential Amino Acid

To answer "Which one of the following is not an essential amino acid?", you need to select an amino acid from the non-essential list. For example, if the options were Valine, Lysine, Methionine, and Alanine, Alanine would be the correct answer as it is non-essential. Other common non-essential options found in questions might include glycine or serine.

Comparison: Essential vs. Non-Essential Amino Acids

Feature	Essential Amino Acids	Non-Essential Amino Acids
Source	Must be obtained from the diet.	Can be synthesized by the body.
Number	Nine.	Eleven.
Examples	Leucine, Tryptophan.	Alanine, Glycine.
Dietary Need	Crucial for regular consumption.	Not required from diet under normal conditions.

Dietary Sources of Amino Acids

Obtaining all essential amino acids is key for a complete amino acid profile. Protein sources are categorized as complete or incomplete.

Complete Proteins

Complete proteins provide all nine essential amino acids. These primarily include animal products like meat, fish, eggs, and dairy. Some plant sources, such as soy and quinoa, are also complete proteins.

Incomplete Proteins

Most plant-based foods, such as nuts and beans, are incomplete proteins, lacking one or more essential amino acids. Vegetarians and vegans can ensure they get all essential amino acids by combining different incomplete protein sources throughout the day.

The Importance of Balanced Amino Acid Intake

Both essential and non-essential amino acids are crucial and work together in the body. A diverse diet with adequate protein supports the body's need for these building blocks. Essential amino acids are fundamental for many functions, while non-essential ones support metabolism and detoxification. A lack of any essential amino acid can negatively impact protein synthesis and overall health.

Conclusion

The key difference is the body's ability to synthesize them. The nine essential amino acids must come from the diet, while the 11 non-essential ones, such as alanine, can be made internally. When asked to identify a non-essential amino acid, look for one that is not among the nine essential ones. A balanced diet with various protein sources ensures sufficient amino acids for optimal health. For more information, consult the Amino acids: MedlinePlus Medical Encyclopedia.

Frequently Asked Questions

Which amino acid is a non-essential amino acid?

Alanine, glycine, serine, and proline are examples of non-essential amino acids because the body can synthesize them.

What are the nine essential amino acids?

The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

What is a conditionally essential amino acid?

A conditionally essential amino acid is usually non-essential but becomes necessary from the diet during illness, stress, or growth.

Do I need to eat non-essential amino acids?

No, dietary intake of non-essential amino acids is not required as the body produces them. However, protein-rich foods contain all amino acids.

What is a complete protein?

A complete protein source contains all nine essential amino acids in sufficient amounts.

Can vegans get all essential amino acids?

Yes, vegans can obtain all essential amino acids by eating a varied diet combining different plant proteins.

Why is a balanced amino acid intake important?

A balanced intake of both types is important for building tissues, producing hormones and enzymes, and supporting health. A deficiency in essential amino acids can disrupt protein synthesis.