AP Syllabus focus:
‘Mitochondria’s inner membrane and folded cristae support coordinated, enzyme-catalyzed reactions that capture energy from macromolecules.’
Mitochondria are specialized organelles that compartmentalise respiration so energy stored in food molecules can be efficiently transferred to ATP. Their membrane architecture creates distinct spaces that localise enzymes, substrates, and gradients.
Core Mitochondrial Architecture
Outer membrane: boundary and exchange
Outer mitochondrial membrane forms a boundary with the cytosol and contains transport proteins that allow many small molecules to pass.
Practice Questions
FAQ
Mitochondrial DNA encodes a small subset of respiratory proteins and RNAs.
Most respiration proteins are nuclear-encoded, synthesised in the cytosol, and imported into mitochondria.
They can increase inner membrane surface area by altering cristae abundance.
They can also increase the concentration of specific inner-membrane protein complexes.
The outer membrane is relatively permissive, but the inner membrane requires specific transporters.
Transport specificity helps control respiration rate by regulating substrate entry.
It is highly protein-rich and selectively permeable.
Its architecture concentrates the machinery that converts energy from substrates into ATP.
High-demand tissues often show greater mitochondrial density and more elaborate cristae.
Lower-demand tissues may have fewer mitochondria with less extensive inner-membrane folding.
