The next steps in cellular respiration take place in a mitochondrion (that's the singular form of mitochondria, one of the cell's organelles). Here's a quick review of what a mitochondrion looks like. For cellular respiration, just pay attention to these three important parts:
• Outer membrane: Just what it sounds like. A membrane on the outside of the mitochondrion. This membrane, and the inner membrane, is made up 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 inter membrane 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:
Real-life mitochondria from a paramecium, seen under a microscope: