Amino Acids: The Fundamental Building Blocks of Life
To understand peptides, you first need to know amino acids — the basic units that make up all proteins and peptides in the human body.
What is an amino acid?
An amino acid is an organic molecule composed of an amino group (NH₂), a carboxyl group (COOH), a hydrogen atom, and a variable side chain (R group), all bonded to a central carbon (alpha carbon). It is the side chain that differentiates each amino acid and determines its unique chemical properties.
20 Standard Amino Acids
The human body uses 20 different amino acids to build all of its proteins. They are genetically encoded and combined in specific sequences determined by DNA.
Essential vs Non-Essential
Of the 20, nine are essential — the body cannot produce them and they must be obtained through diet. The other 11 are non-essential, as the body can synthesize them.
Classification of the 20 Amino Acids
Essential (9)
Non-Essential (11)
Functions of Amino Acids in the Body
Protein Synthesis
Form the structure of muscles, organs, skin, hair and nails through protein assembly.
Enzymes & Catalysis
Make up enzymes that accelerate thousands of essential chemical reactions in metabolism.
Cell Signaling
Serve as precursors for neurotransmitters (serotonin, dopamine) and hormones.
Immune System
Form antibodies and other proteins in the defense system against infections.
Transport
Make up transport proteins like hemoglobin, which carries oxygen in the blood.
Energy
When needed, can be converted to glucose for energy production.
The Peptide Bond
The peptide bond is the chemical link that joins amino acids together. It occurs when the carboxyl group (-COOH) of one amino acid reacts with the amino group (-NH₂) of the next, releasing a water molecule (condensation reaction). This covalent bond is strong and stable, forming the "backbone" of all peptides and proteins.
What Are Peptides?
Peptides are short chains of amino acids joined by peptide bonds. They differ from proteins mainly in size: while proteins typically contain more than 50 amino acids and form complex three-dimensional structures, peptides are smaller, simpler molecules.
Classification by Size
2–10
amino acids
Oligopeptide
Ex: GHK-Cu (3 aa), KPV (3 aa), Epithalon (4 aa)
10–50
amino acids
Polypeptide
Ex: BPC-157 (15 aa), Sermorelin (29 aa), MOTS-C (16 aa)
50+
amino acids
Protein
Ex: Insulin (51 aa), HGH (191 aa)
How Do Peptides Work?
Peptides act as molecular messengers in the body. They bind to specific receptors on the cell surface, triggering precise biological responses. Each peptide has affinity for specific receptors, which explains why different peptides have distinct effects.
Signaling
The peptide circulates through the body and finds its target receptor on the surface of a specific cell. The three-dimensional shape of the peptide fits into the receptor like a key in a lock.
Activation
The peptide-receptor binding activates a cascade of intracellular signals. Messenger proteins inside the cell transmit the signal from the receptor to the nucleus or other organelles.
Biological Response
The cell responds according to the signal received: it may produce more of a protein, activate a gene, release a hormone, initiate a repair process, or modulate an inflammatory response.
Main Peptide Categories
Research peptides are classified according to their primary biological functions. Each category acts on specific systems and receptors in the body.
GH Secretagogues
Stimulate the natural release of growth hormone (GH) by the pituitary. Act on GHRH or GHS-R1a receptors (ghrelin receptor).
Examples: Ipamorelin, Sermorelin, GHRP-2, GHRP-6
Healing & Recovery
Promote tissue repair, angiogenesis, and inflammatory modulation. Act on multiple cellular recovery mechanisms.
Examples: BPC-157, TB-500, GHK-Cu
Metabolic
Influence energy metabolism, fat oxidation, and insulin sensitivity. Some mimic fragments of metabolic hormones.
Examples: AOD-9604, MOTS-C, HGH Frag 176-191
Cognitive & Neuroprotective
Modulate neurotransmitters, promote neuroplasticity, and offer protection to the central nervous system.
Examples: Selank, Semax, Epithalon
Hormonal Regulation
Act on the hypothalamic-pituitary-gonadal (HPG) axis modulating the production of reproductive hormones such as LH, FSH and testosterone.
Examples: Gonadorelin, Kisspeptin-10, Triptorelin
Cosmetic & Skin
Stimulate the production of collagen, elastin and melanin. Act on the remodeling and protection of the skin extracellular matrix.
Examples: GHK-Cu, Melanotan II
Natural vs Synthetic Peptides
Natural Peptides
Naturally produced by the human body. The body synthesizes hundreds of different peptides that regulate processes such as digestion, sleep, growth, immune response and mood. Examples include endorphins (pain relief), insulin (glucose regulation) and oxytocin (social bonding).
Synthetic Peptides
Produced in a laboratory through solid-phase peptide synthesis (SPPS). They can be exact replicas of natural peptides or modified versions to increase stability, half-life, or selectivity. They are typically supplied in lyophilized (powder) form and need to be reconstituted before use in research.
Lyophilization: Why Are Peptides Supplied as Powder?
Research peptides are supplied as lyophilized (freeze-dried) powder for stability reasons. Lyophilization removes all water from the solution by sublimation at low temperatures and vacuum, preserving the molecular structure intact. In this dry form, peptides can be stored for months or years without significant degradation.
Before use in research, the lyophilized peptide must be reconstituted with bacteriostatic water following specific techniques that preserve its integrity.
Important Notice
The information on this page is exclusively for educational and technical reference purposes. Research peptides are not approved for human consumption. Always consult a qualified healthcare professional. This content does not constitute medical advice, diagnosis or treatment.
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