Glycolysis Match Game by Athletic Design
Old Flash-version here

Learn glycolysis! A serious yet easy-to-follow guide & game.

There are three game variants

Interactive Lecture

The ten enzymes and the eleven molecules of glycolysis are explained step by step. For each step a simple touch action is required to verify that you follow the explanation.

Homework Assignment

A playground for study! You are given a score but don't be afraid of mistakes. As a beginner you may play around and learn by trial and error. However, you should earn a score of >80 before trying the Exam!

Stressful Exam

You have 60 seconds to match as many cards as possible. Match all before time runs out to earn a time bonus. Additional points can also be gained by matching a card of the current bonus category.

Energy by breaking up sugar molecules

"Glycolysis" means "sugar breakdown". The sugar molecule glucose contains six carbon atoms and is broken down to two pyruvate molecules of three carbon atoms each. This breakdown takes part inside every cell (from bacteria to human) in ten steps (chemical reactions assisted by enzymes) and yields energy.

Fast grabbing of the low hanging fruits …

However, it is far from a complete breakdown. Inside the cell's mitochondria the breakdown is continued (into six CO2) and the energy yielding is taken much further. As an analogy, think of the sugar molecule as a tree with 38 apples*. Only 2 apples are harvested during glycolysis. But these are the low hanging fruits so by the time the mitochondrion painstakingly has harvested the other 36, glycolysis may already have picked 3600 more!

… leads to build-up of pyruvate …

In other words: Glycolysis is a time efficient but resource inefficient way of producing energy. The slowness of the mitochondrial reactions can be compensated by lots of mitochondria. However, there are relatively few mitochondria but lots of glycolytic enzymes in muscles, so even at rather light exercising the mitochondria can’t keep up and there is a build-up of pyruvate.

… which is converted to lactic acid (and moved to the liver).

Depending on the enzymes present, accumulated pyruvate is then converted to either lactic acid (e.g. in humans) or ethanol (e.g. in yeast cells). The conversion to lactic acid resets a key molecule of glycolysis - the hydrogen/electron carrier NAD - so that glycolysis can keep going.

Accumulation of lactic acid quickly leads to loss of muscle function, so it must be transported out of the muscle cell into the blood. Some is shuttled to other cells that do not experience a build-up of pyruvate, to be converted back to pyruvate and enter those cells’ mitochondria. The rest enters the liver, which can convert it back to glucose for later use. This reversion actually costs more energy than glycolysis has yielded and is ultimately dependent on energy harvested inside the mitochondria of the liver.

Mitochondrial oxidation

When the mitochondrial reactions keep up with glycolysis, the conversion to lactic acid is not necessary as NAD is also reset inside the mitochondrion. This happens in the final chain of reactions where the hydrogen/electron carried by NAD is ultimately grabbed by electron-hungry oxygen, which then forms water and releases a lot of energy. The original carrier of hydrogen was glucose, which by now has been broken down to hydrogenless CO2.

The amount of oxygen is often the limiting factor during full-body exercising, as lots of mitochondria then have to share what oxygen the lungs, heart, and red blood cells can supply.

*An apple represents an ATP-molecule We can stretch the analogy further by letting the whole tree represent 100 units of energy of which only 38 (the apples/ATPs) are directly useable by humans. The rest of the tree is burned down so that the remaining 62% of energy is released as heat.