What are peptides, using three glossary entries
What are peptides, on the National Human Genome Research Institute talking glossary, is a short chain of amino acids linked by chemical bonds the page calls peptide bonds. This article follows that entry and the two entries beside it, amino acids and protein. It is not medical advice. It does not name a product, a dose, a seller, or a price.
The NHGRI peptide glossary entry is the definition used here. The amino acid entry and the protein entry are the other two pages. The site peptide glossary can point at the same three words. Length cutoffs printed on the entries stay on the entries.
What are peptides, next to the longer words
The peptide entry gives one object: a short chain. It gives the link between the units: a peptide bond. It then names a longer chain a polypeptide, and it says the proteins made inside cells are made from one or more polypeptides. That is the ladder. What are peptides is the short-chain rung. The protein entry's folded molecule is a different rung.
The amino acid entry calls an amino acid the fundamental molecule that serves as the building block for proteins. It says a protein consists of one or more chains of amino acids, called polypeptides, whose sequence is encoded in a gene. The count of amino-acid kinds is printed on that entry. This article does not copy the count.
The protein entry calls proteins large, complex molecules made up of one or more long, folded chains of amino acids, each called a polypeptide, whose sequences are determined by the DNA sequence of the protein-encoding gene. Folding is on that page. This article does not add a shape or a use.
Put the three lines together and the vocabulary is finished. An amino acid is the unit. A peptide is a short chain of those units, joined by peptide bonds. A polypeptide is the longer chain the peptide entry names. A protein is one or more folded polypeptide chains, as the protein entry names them.
How the three entries agree
What are peptides should be answered before any other clause: a short chain of amino acids linked by peptide bonds. The same glossary calls a longer chain a polypeptide. Proteins are made from one or more of those longer chains. After those three sentences, the distinction is done.
The amino acid entry and the protein entry both tie the order of the chain to a gene. The amino acid entry says the sequence is encoded in a gene. The protein entry says the sequences are determined by the DNA sequence of the protein-encoding gene. A reader can hold both sentences without adding a step between them.
The narration on the peptide entry compares amino acids to separate blocks and a few of them locked together to a peptide. That illustration is on the page, credited there to Sara Chandros Hull, Ph.D. It does not replace the definition sentence.
Photo: ChromeGames923, Backlit laptop keyboard keys, CC BY-SA 4.0. The photograph is only a credit for the image. It is not part of the definition.
The answer, in the glossary's order
Open the peptide entry and read the short chain and the peptide bond. Open the amino acid entry and read the building block and the gene. Open the protein entry and read the folded chain. What are peptides has then been answered in the only way these three pages support.
The newsroom does not sell a peptide on this page, and the page does not tell anyone to take one. A shop, a coupon, and a price are not in the three entries. A regulatory question belongs in a separate story, and only when the keyword map already has that primary and an agency document is the source.
If the institute edits a definition, the live entry wins. Until then, the answer stays in this order. What are peptides is a short chain of amino acids linked by peptide bonds. The longer chain is a polypeptide. A protein is one or more folded polypeptides. Those are the three sentences.