Jeopardy! category: BIOLOGY CLASS (12-02-2014)
$400 clue: By definition, a polypeptide is a chain of these linked together by peptide bonds
The gist: Life is full of chains. Nucleic acids are chains of nucleotides. Polysaccharides are chains of sugars (which one contestant offered as an incorrect response to this Triple Stumper). Polypeptides, in their turn, are chains of amino acids. An amino acid is one of the basic building blocks of life, defined as a molecule with both an amine and a carboxylic functional group, plus a third branch that gives it its own unique traits. A peptide bond (hence “polypeptide”) is a bond between the amine group of one amino acid and the carboxylic group of another, linking the molecules together and releasing a single molecule of water. Note that proteins are also molecules made of amino acids linked with peptide bonds, but are usually much larger than polypeptides (often including several polypeptides within their structure), can include other non-polypeptide groups, and, most importantly, are biologically functional – they perform a specific function needed by their cell.* Proteins are polypeptides, but polypeptides are not necessarily proteins. Polypeptides can occur in cells through the breakdown of larger molecules (like casein, a protein found in dairy products and important in cheesemaking) or through synthesis (such as by ribosomes when they’re putting together proteins).
Polypeptides have also recently been in the news with regard to research into PPMOs (that’s peptide phosphorodiamidate morpholino oligomers, for the curious) as possible alternatives to antibiotics, which have been causing some problems as the nasty bacteria develop resistances faster than we can make medicine to kill ’em. Because they function through an entirely different mechanism than traditional antibiotics (they bind to specific bacterial genes preventing their expression), current bacteria don’t have resistance against PPMOs, and it may be a lot more difficult for them to evolve such resistances in the future.
The clue: A straightforward question about a late-high-school level biology fact. I’m a bit surprised it was a Triple Stumper (though I will sheepishly admit I couldn’t recall it either), but then I don’t know what the contestants’ majors are – if they’ve mentioned them in interviews, let me know in the comments. No real way to figure it out from context, either. Of note is that contestants guessed both carbons and sugars – there are tons of different kinds of carbon chains out there, and a chain of sugar is a polysaccharide, as I said up top.
In Jeopardy!: “Polypeptide” has only shown up in two clues previously, one pretty much the same as this one, and the other asking about insulin, a polypeptide hormone. “Peptide” pops up another two clues, one about endorphins (another hormone), and one wordplay clue. Amino acids are the things you should be concerned about. They show up in over 30 clues, but sadly not much is consistent among them – some ask about specific examples, some ask about their chemistry, and some are concerned with how they show up in food. The best word to associate with amino acids is “essential” (and, conversely, “non-essential”), which defines the nine amino acids that humans can’t synthesize themselves and therefore must be ingested. If you see either of those in a category about biology, health, or the like, the correct response is likely “amino acid.” Beware, though, of “essential oils,” which have little to do with human biology but are used in cooking and aromatherapy, and have also shown up in a few clues.
* Polypeptides can have biological functions too, but a protein is defined by its function.