Questions: Identify and briefly describe the two phases of oxidative phosphorylation

Oxidative phosphorylation is a crucial process in cellular respiration that occurs in the mitochondria. It consists of two main phases:

1. Electron Transport Chain (ETC):

   • This phase involves a series of protein complexes and other molecules embedded in the inner mitochondrial membrane. Electrons are transferred through these complexes, starting from electron donors like NADH and FADH2, which are generated in earlier stages of cellular respiration. As electrons move through the chain, they release energy, which is used to pump protons (H⁺ ions) from the mitochondrial matrix into the intermembrane space, creating a proton gradient across the membrane.

2. Chemiosmosis:

   • In this phase, the proton gradient created by the electron transport chain is used to drive the synthesis of ATP. Protons flow back into the mitochondrial matrix through ATP synthase, a protein complex that acts as a molecular turbine. The flow of protons through ATP synthase provides the energy needed to convert ADP and inorganic phosphate into ATP, the primary energy currency of the cell.

In summary, oxidative phosphorylation involves the electron transport chain creating a proton gradient, and chemiosmosis using that gradient to produce ATP.