Understanding Amino Acids in General

The Basics of Amino Acids

Amino acids are organic compounds made up of the elements carbon, hydrogen, nitrogen, oxygen, and sometimes sulfur. They are the building blocks of proteins, and serve many other critical roles in your body. The human body uses 20 amino acids to build proteins.

• Essential Amino Acids: These are 9 amino acids, including Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine, which the human body cannot produce on its own and therefore must be obtained from the diet.
• Non-essential Amino Acids: This group comprises 11 amino acids, including alanine, asparagine, aspartic acid, and glutamic acid, that the human body can produce on its own.

Functions and Importance of Amino Acids

Amino acids play a central role in the biological processes, carrying out various functions such as building of proteins and synthesis of hormones and neurotransmitters. Essential amino acids are especially important for growing, repairing body tissues and maintaining good health, and more

• Major players in wound healing and tissue repair
• Used in the creation of enzymes assisting in digestion, and the antibodies that protect us against diseases
• Required for synthesis of hemoglobin, which transports oxygen throughout the body

Naturally Occurring Amino Acids

As mentioned earlier, nature has gifted us with an array of essential and non-essential amino acids naturally. Each of these amino acids serves distinctive roles and functions. For instance,

• The amino acid Tyrosine forms part of all protein structures, and is key to formation of neurotransmitters like dopamine and adrenaline
• Isoleucine helps with blood clotting and energy regulation
• Tryptophan, which the body converts to serotonin that promotes healthy sleep patterns

Identifying Non-Naturally-Occurring Amino Acids

What are Synthetic Amino Acids?

In contrast with the naturally-occurring amino acids, there are synthetic or non-naturally-occurring amino acids. These are typically created in a lab setting for various purposes, such as research, medicine, and dietary supplements. They might even have structures and functions similar to their naturally-occurring counterparts but some differences exist.

• Contrasting the naturally-occurring ones, which are predominantly "L-forms,", synthetic amino acids can be "D-forms"
• There's no upper limit on how many different synthetic amino acids can exist
• Often used to study the workings of proteins more closely

Examples of Non-Naturally-Occurring Amino Acids

Several synthetic amino acids exist. These include the likes of Beta-Alanine, Citrulline, and D-Aspartic Acid, etc. They are often used to gain health advantages and enhance performance

• Beta-Alanine, a common ingredient in workout supplements that's linked to improving muscle endurance
• Citrulline, known for improving blood flow and reducing blood pressure
• D-Aspartic Acid, which can boost testosterone in men

The Outsider: Non-Naturally Occurring Amino Acid

Unveiling the Non-Naturally Occurring Amino Acid

The world of amino acids is intricate and fascinating, replete with many variants. However, one notable outsider in the realm of naturally-occurring amino acids is D-Aspartic Acid. Found in supplements targeting testosterone increase, it is a synthetic creation in labs, not occurring naturally in foods or the human body. No mainstream diet or metabolism path innately includes this compound. In this light, answering the initial question - "which of the following is not a naturally-occurring amino acid?" - the response would be: D-Aspartic Acid.

• It is formed via an enzymatic reaction in the testes and pituitary gland
• Plays a role in the release and synthesis of LH (luteinising hormone) and testosterone
• Though synthetic, it's useful for boosting testosterone in males.