You’ve been studying cellular organelles including mitochondria in class.  In my lab at Auburn University, we study how mitochondria impact reproduction and aging.  Studying mitochondria can be challenging.  Mitochondria are so small that you could fit about 200 mitochondria end to end between the lines indicating 1 mm on a ruler. The first thing we have to do to study these tiny organelles is to release them from the cells.  We isolate mitochondria from the cells of a tissue by using an instrument called a homogenizer that vibrates the tissues until the cells lyse, or burst.  Then, we centrifuge the homogenized tissue to separate organelles by their weight.  The heavy mitochondria are forced to the bottom of the tube by centrifugal force (or the force generated away from the center when spinning an object).  We then collect the layer at the bottom of the tube that has the mitochondria in it. Now that we have isolated the mitochondria, we can measure any of a number of things.

 

For our studies, we focus on the function of the electron transport chain within the mitochondria.  One variable that we are interested in is the respiration rate of the mitochondria.  Remember the equation for cellular respiration that you learned in class?

 

 

 

Glucose is a source of nutrition so we give the mitochondria plenty of nutrients - not exactly glucose but a product of the breakdown of glucose, lipids, or proteins by the cell or mitochondria.  We also make sure that the mitochondria have lots of oxygen.  We can measure how well the mitochondria work by measuring the change in any of the compounds in the cellular respiration equation. We could measure the disappearance of glucose or oxygen or we could measure the gain in carbon dioxide, water, or ATP.  Measuring the disappearance of oxygen gives us the most accurate and repeatable results, so that's what we measure. We put the mitochondria in a chamber with nutrients, oxygen, and ADP and measure how quickly the mitochondria use up oxygen.

 

We also measure a few other really important variables associated with mitochondrial health including the number of mitochondria, damage to mitochondria, and compounds that help to prevent damage called antioxidants.

 

Dr. Wendy Hood

March 1, 2020