SAS' Cell Biology Page

Anaerobic Respiration (Glycolysis)

Just like a car engine that needs a spark energized from the car's battery before it can convert gasoline into energy, anaerobic respiration (glycolysis), also needs a boast of energy to get started. So in the first step, glucose becomes charged by 2ATP with a little help from an enzyme, receiving two organic phosphates from the 2ATPs. Glucose becomes Fructose-1,6-phosphate, for the phosphate has been attached to the 1st carbon and the 6th carbon on glucose.

This charge from ATP pushes the process along, like being pushed uphill, reaching the top, and down you have a fast coast downhill. After this step, Fructose 1,6-diphosphate is split in half by the enzyme Triose phosphate isomerase, forming two glyceraldehyde-3-phosphate, the phosphate being attached to the third carbon of glyceraldehyde.

Now its time to get a little of the energy back. In the next two steps, energy is released from Glyceraldehyde-3-phosphate, producing NADH and ATP. Since we have two Glyceraldehyde-3-phosphates, the 2ATP used earlier to start the reaction has been returned, plus an extra 2NADPH have been made.

Notice that the big change to glyceraldehyde is the addition of another organic phosphate. That sets up the next step, where ATP is made.

Now, lets go after that last organic phosphate group, and lets make some more ATP.

So at the end of anaerobic respiration (glycolysis), 2ATP were used to start the reaction, but 4ATP and 2NADH were made, a net product of 2ATP and 2 NADH. Energy has been released from glucose now, which could be used for that run, or the boring lecture.

The end product is pyruvate, but pyruvate is not very stable in our cells. So pyruvate is converted into lactic acid, using NADH. The following chemical equation shows how pyruvate is converted.

Lactic acid gives your muscles that burn after a long run, or strenuous work over a long period.

Ahh, but you are yawning now. Need a little oxygen to pull more energy from that molecule of glucose. Now we are entering the pathways of aerobic respiration.