DR. IFFIC LECTURE 3:TRYPTOPHAN AND OTHER

MIGHTY MOLECULES

We have another question from “Jimmy,” who asks, “What is tryptophan? How does it make you sleepy?

Welcome back, seekers of knowledge! I trust you have been hard at work since our last meeting, grasping cosmic truths and refurbishing your underground lairs. Dmitri

Alekseyevich, what is our topic for today’s lecture?

Molecular biology?

“Jimmy” again, eh? Well, be that as it may, let us delve into the world of molecular biology.

STILL NOT JIMMY.

Nooks and crannies?

Yes indeed. This “Jimmy” character may have expected to get off the hook with a cursory statement about “hormone this” and “enzyme that,” but instead, we are going

to examine the underpinnings of life itself, and how it is all based on nooks and crannies.

I thought protein was something that you needed in your diet.

Nooks and crannies, Dmitri Alekseyevich. The nooks and crannies of really big molecules, such as proteins.

But what are proteins, exactly?

That is true, because our bodies build the proteins they require from the food we digest. Proteins are required for just about every biological function. If you think of a living cell as a machine, proteins are the gears. And the batteries. And the switches.

And the loose parts inside that have been making that rattling noise ever since that one time you dropped it on the floor.

And a molecule is a collection of atoms that are bound together by their electrons, right?

Proteins are fantastically complex molecules that interact with each other to make various things happen within living cells.

How can protein molecules be so large?

Yes, as we learned in previous lectures. But proteins are the Godzillas of the molecular world. A lot of molecules found in nature are very simple, like carbon dioxide: two oxygen and one carbon. Or sodium chloride: a repeating matrix of sodium and chlorine. But proteins can contain hundreds of atoms in dazzlingly

complex arrangements.

Carbon DioxideSodium Chloride

Lysozyme (a protein)

So how does this get into nooks and crannies?

Primarily because they have a lot of carbon atoms. Carbon is a very versatile atom: it can form up to four different bonds with other atoms. That allows a molecule to grow

very large and complex: you can get a long chain of carbon atoms going with lots of other atoms branching off to the sides – including more carbon. This diagram shows carbon atoms in black, and demonstrates how they can stack into chains. And this is

just a little guy as far as proteins go – they can get much, much bigger.

So life is basically a bunch of molecules bumping into each other and changing shape?

Because proteins are so complex, their outer surfaces are full of little bits sticking out in various shapes, making little nooks and crannies. Sometimes these nooks and crannies make it easier for chemical reactions to take place near the protein. And when these nooks and crannies line up just the right way on two different proteins, the proteins

link up and interact – bending, or twisting, or even creating a new protein altogether. These changes are due to the shapes of the proteins and to the chemical interactions

between the atoms that make up each nook and cranny. Proteins are just one example of this -- interactions like this happen with other biological molecules too. And these

interactions form the basis of biological processes.

Well, in a purely mechanical sense, yes. For example, when you digest food, your gut cells use proteins called enzymes to break the food down into smaller chemicals.

When you move your body, your muscle cells use proteins called actin and myosin to create the motion. And when you see a sabertooth tiger activating its actin and myosin in order to digest you with its enzymes, your glands release a chemical called adrenalin

that interacts with various cells in different ways to prep you for action and generally make you go, "HOOLABALOOLA!"

(Adrenalin is not a protein, but it’s another example of a complex molecule that works via nooks and crannies.)

So that’s why DNA is so important.

Well, you get the raw ingredients -- smaller molecules called amino acids. The specific proteins your body needs are then synthesized by your DNA (which is a nucleic acid,

another type of Godzilla-sized molecule).

And you get all these proteins from eating?

And tryptophan -- that's a type of protein?

Yes, the types of proteins that are synthesized by your DNA determine how your cells develop and how they interact with their environment. And proteins from outside your body can affect you as well. Snake venom contains a mix of proteins that interfere with important biological processes. Viruses use proteins to "unlock" cell membranes so that they can move in and take over. Even the itchiness of mosquito

bites is due to proteins. (These ribbon models of proteins may look different from the ball-and-stick models, but they represent they same sort of thing – Godzilla-sized

molecules.)

So how does it make you sleepy?

Not quite. Tryptophan is an amino acid, one of the chemical building blocks of proteins. As you can see, it's much simpler and smaller than a full-fledged protein --

even though it's still much more complex than something like carbon dioxide or sodium chloride.

Well, keep in mind that the whole turkey-tryptophan-sleepiness thing is a bit of an urban legend. There's no clear evidence that tryptophan all

by itself makes you sleepy, and in any case turkey doesn't contain unusual amounts of the stuff. But tryptophan is a component of a

simple protein called melatonin, and melatonin definitely makes you sleepy, so it's possible that having lots of tryptophan floating around

would lead to more melatonin being produced.

Tryptophan Melatonin

So if tryptophan makes you sleepy, it’s probably because it gets turned into melatonin, which makes you sleepy because of the ways in which in interacts

with other molecules in your body – on account of its nooks and crannies.

Yes – if tryptophan makes you sleepy in the first place.

But it might not.

No, it might not. More research is required. Fortunately, tryptophan-laden substances are available for sale at a variety of nearby

foodservice establishments. Let us go forth and consume them for Science.