Understanding Amino Acids and Their Importance
Amino acids serve as the building blocks of proteins and play numerous critical roles within the body. Getting adequate amino acids from one's diet proves essential for good health. When exploring amino acids, a common question arises regarding which compounds qualify as amino acids and which do not.
Defining Amino Acids
Amino acids consist of compounds containing an amino group (-NH2) along with a carboxylic acid group (-COOH). Over 500 amino acids exist in nature, but only 20 comprise the primary amino acids that join together to form proteins.
These 20 main amino acids differ according to their side chains (R groups). The properties of the side chains determine each amino acid's chemical behavior and protein function. Amino acids bond together via peptide bonds in varied sequences to construct protein molecules.
Classifying Amino Acids by Side Chain Groups
Two categories divide the 20 primary amino acids based on the properties of their side chain groups. These include:
Essential vs. Non-Essential Amino Acids
Amino acids also differ in terms of whether or not humans can produce them internally. Essential amino acids cannot get synthesized by the human body quickly enough to meet metabolic demands. Instead, these amino acids must come from one’s diet. Non-essential amino acids do get produced naturally within adequate quantities.
The essential amino acids include: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Non-essential amino acids include: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine and tyrosine.
Which Compounds Do Not Qualify as Amino Acids?
While amino acids feature commonalities in their structure and function, not all nitrogen-containing compounds meet the criteria to classify as amino acids. Understanding which compounds do not qualify provides greater clarity around this molecule category critical to life and health.
Nucleic Acids: DNA and RNA
Nucleic acids such as DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) play essential roles relaying genetic code and facilitating protein synthesis. However, they do not directly join together to form proteins. While their nitrogenous bases contain nitrogen, nucleic acids lack the amino and carboxyl groups critical to amino acid definition.
Triglycerides
Triglycerides function as the main constituents of human and animal fat tissues. They consist of a glycerol backbone bound to three fatty acid chains. While amino acids feature chains of carbon and hydrogen, the structure of triglycerides differs considerably. Triglycerides do not possess amino or carboxyl groups either.
Glucose
Glucose provides critical energy to cells in the form of blood sugar and glucose polymers called glycogen. As an aldehyde rather than a compound containing amine and acid groups, glucose differs significantly from amino acids in its chemical structure and function within the body.
Enzymes
Enzymes facilitate nearly all biochemical reactions within the body to sustain life. While enzymes contain protein synthesized from amino acids, the proteins themselves do not constitute amino acids. Enzymes rely on their globular protein structure to catalyze reactions rather than joining together to build bodily structures.
Vitamins
Vitamins also play irreplaceable roles within the body as vital organic nutrients. However, vitamins do not polymerize into proteins. Their chemical structures vary greatly from the standard amino acid composition. Most vitamins get classified as either water soluble (B complex and C) or fat soluble (A, D, E and K).
Why Properly Identifying Amino Acids Matters
Understanding which compounds do and do not qualify as amino acids holds importance for several health-related reasons explained below.
Protein Synthesis
Amino acids combine in highly specific sequences and conformations to conduct the thousands of functions executed by protein molecules. Properly identifying amino acids enables one to understand this translation from DNA to functional proteins.
Dietary Protein Sources
Identifying optimal food sources of amino acids allows one to plan a diet containing adequate total and essential amino acids for growth and repair. These foods include meat, fish, poultry, eggs, beans, nuts and soy.
Supplemental Amino Acids
In certain medical conditions involving suboptimal protein digestion and absorption, physicians may prescribe free amino acid supplements. Recognizing which compounds qualify as essential amino acids ensures these supplements get properly formulated and administered.
Metabolic Health
Amino acid balance proves critical for optimal energy production and metabolic health. The body requires amino acids not only for tissue building but also to synthesize glucose and ketones. Maximizing metabolic output requires adequate intake of all essential amino acids.
Examples of Compounds Often Mistaken for Amino Acids
Despite the distinct categorization of amino acids, confusion continues to exist regarding which nitrogenous compounds qualify. The following represent examples of substances often mistakenly grouped with amino acids.
Creatine
Creatine plays a key role supplying energy to muscle and nerve cells. Though it contains a nitrogenous base called guanidino, its chemical structure lacks peptide bonds linking amino and carboxyl groups definitive of amino acids.
Heme
Heme constitutes a complex organic compound featuring iron bound to a porphyrin ring. Heme occurs in hemoglobin which transports oxygen through the bloodstream. The lack of amine and acid groups excludes heme from the amino acid family.
Acetylcholine
The neurotransmitter acetylcholine participates in motor neuron signaling. While it possesses a basic amine component, the rest of its structure and function within the nervous system differs entirely from amino acid characteristics.
Adrenaline
Also known as epinephrine, the hormone adrenaline plays a famous role in the fight-or-flight response. Adrenaline’s catecholamine structure binds to different receptors to achieve unique effects from those of protein-building amino acids.
Future Research on Amino Acid Roles
Scientists continue making strides elucidating the many critical bodily roles of amino acids. Further research aims to uncover new functions of amino acids relating to gene expression, cell signaling, neurotransmitter balance and immunity optimization just to name a few.
Given amino acids’ essentiality to human life itself, new findings will further demonstrate the importance of properly identifying which unique compounds do and do not comprise this special category of organic molecules.
FAQs
What are the 20 main amino acids used to build proteins?
The 20 amino acids that join together via peptide bonds to form proteins include both essential and non-essential types. Essential: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine. Non-Essential: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, tyrosine.
Do all compounds containing nitrogen qualify as amino acids?
No. While amino acids contain nitrogen, not all nitrogenous compounds meet the criteria to be classed as amino acids. Nucleic acids, glucose, triglycerides, enzymes and vitamins contain nitrogen without conforming to the definition of an amino acid.
What distinguishes amino acids from other molecules?
The distinguishing structure of amino acids includes an amino group (-NH2) and carboxyl group (-COOH). These groups allow amino acids to link together via peptide bonds and form protein molecules that perform essential bodily functions.
Why does properly identifying amino acids matter?
Correctly distinguishing between amino acids and other compounds holds importance for optimally synthesizing proteins, getting adequate dietary amino acids, effectively supplementing essential amino acids, and maintaining metabolic health.
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