B2.2.4 Adaptations of the mitochondrion for production of ATP by aerobic cell respiration (HL) Notes

Mitochondrial Adaptations Optimize ATP Production in Aerobic Respiration

1. The mitochondrion is enclosed by an outer membrane and a highly folded inner membrane, creating distinct compartments for different stages of aerobic respiration.
2. This separation allows specific biochemical processes (e.g., Krebs cycle in the matrix, oxidative phosphorylation on the inner membrane) to occur in optimal conditions.

The Outer Membrane Is A Controlled Gateway

1. It is selectively permeable, allowing small molecules like pyruvate and oxygen to enter while excluding larger, potentially disruptive molecules.
2. This regulation helps maintain a suitable environment for the complex reactions inside the mitochondrion.

The Intermembrane Space Is A Proton Reservoir

1. Protons (H⁺) are pumped into this narrow space during the electron transport chain (ETC), creating a steep concentration gradient.
2. The small volume of this space ensures that even a modest influx of protons quickly raises the proton concentration, crucial for ATP synthesis.

The Inner Membrane Is The Site of ATP Production

1. This membrane hosts the ETC and ATP synthase, the key proteins in oxidative phosphorylation.
2. Its folded structure (forming cristae) significantly increases surface area, maximizing the number of ETC proteins and boosting ATP output.

Cristae Maximizes Surface Area

1. Cristae are folds in the inner membrane that dramatically expand its surface.
2. More surface area allows more ETC and ATP synthase complexes to be embedded, leading to greater ATP production.

Embedded Proteins Fuel ATP Production

1. The electron transport chain passes electrons and pumps protons into the intermembrane space, setting up the proton gradient.
2. ATP synthase harnesses this gradient to convert ADP and inorganic phosphate into ATP, the cell’s primary energy currency.