Biochemistry Casino: Glycolysis Black Jack

“Money won is twice as sweet as money earned.” The Color of Money

Teaching has kept me busy since my last post. The days leading up to midterms, the grading and the office visits by concerned students in the aftermath have been too full for blog writing. In my biochemistry lecture course, the students and I are making our way through the core metabolic pathways, and I’m trying to come up with creative ways of getting the main ideas across.

 First stop: Glycolysis Blackjack

Glycolysis is a universal metabolic pathway for all organisms that consume glucose. (Yes, that includes plants. They just happen to make their own glucose from sunlight and CO₂ instead of eating other organisms.) As far as energy-yielding pathways go, it’s not that complex. Glucose molecules are converted to pyruvate yielding a net of 2 ATP molecules. However, the names of the enzymes and the metabolic intermediates all start to sound the same and it’s easy to get lost in the details. Here’s an analogy to keep the overall picture in mind.

ATP is often referred to as the biochemical cash of the cell. The simplest game to win some ATP is at the glycolysis black jack table.

First, you have to pay to play. Invest an ATP to get your cards.

Congratulations! Glucose-6-Phosphate is just like being dealt a pair of aces.

If you’re dealt this hand at any casino biochemistry or otherwise, your next move is to split those cards into two hands. (You’ve either got 2 or 12 and the chances of you beating the dealer are much better if you know you are starting with an ace.) As in any casino, you have to pay to split; so you invest another ATP. In glycolysis, you’re splitting a 6 carbon sugar into 2 3-carbon molecules (glyceraldehyde 3-phosphate).

In this contrived situation at the biochemistry casino, betting is limited to your investment. However, when you get your second card for both of your hands, you get jacks. Black jack on both hands. You win! Your winnings on one hand mean you break-even on your investment. Your winnings on the other hand mean you net back your initial investment (2 ATP). In glycolysis, the two molecules of glyceraldehyde 3-phosphate can each be used to yield 2 ATP molecules, giving a net of 2 ATP from glucose.

Sure, it’s not the drama of winning at slots, roulette or the lottery. But at this casino, you always get these cards. If you can ante in the first ATP molecule, you’ll get a pair of aces. If you can ante in the second ATP, you can split them and get jacks and double your investment. Every. Time. Sure, betting is limited, but if you’re guaranteed to win, you would sit at that table all day and all night. And you do. Eventually, you take those winnings and those cards to another table with higher stakes, but that will be a separate analogy. Other organisms make a perfectly good living at this table alone using glycolysis coupled with fermentation.

Of course, there isn’t a money casino in the world that works this way. The house always wins. But you should really split those aces when you get them. That’s still good advice.

Here’s a link to the BiochemistryBlackJack Powerpoint slide with animation if you’re interested in using the analogy.

Johnna

A special thanks to my husband SuperChef for patiently explaining the finer details of blackjack to me to make this analogy work.