Ultrastructure of a Mitochondrion
Key Components of Mitochondrial Structure
1. Outer Membrane
- Smooth, continuous membrane that forms the external boundary
- Contains special proteins called porins that allow selective passage of molecules
- Relatively permeable to small molecules and ions
Think of the outer membrane as a security checkpoint that controls what enters and exits the mitochondrion.
2. Inner Membrane
- Highly folded structure creating numerous inward projections (cristae)
- Much less permeable than the outer membrane
- Contains important proteins including:
- Electron transport chain components
- ATP synthase enzymes
- Transport proteins
The inner membrane's impermeability is crucial for maintaining the proton gradient needed for ATP production.
3. Cristae
- Foldings of the inner membrane that increase surface area
- Where most of the electron transport chain components are located
- Critical for maximizing ATP production capacity
The more cristae a mitochondrion has, the more ATP it can produce. This is why muscle cells have mitochondria with more cristae than other cells.
