Following glycolysis, the next process in cellular respiration takes place in a mitochondrion (that's the singular form of "mitochondria," the cell's powerhouse organelles). Let's quickly review what a mitochondrion looks like. For cellular respiration, pay attention to these three important parts:

• Outer membrane: Exactly what it sounds like. It's a membrane on the outside of a mitochondrion that consists of a phospholipid bilayer, just like the plasma membrane that surrounds the cell.
• Inner membrane: A second membrane on the inside of the outer membrane. The space between the inner and outer membranes is called the intermembrane space. The space on the inside of the inner membrane is the mitochondrial matrix.
• Cristae: These are wrinkles formed by folding of the inner membrane. The cristae provide a large surface area for cellular respiration, particularly the electron transport chain.

An up-close diagram of a mitochondrion


Up close and personal with a mitochondrion from a paramecium