(N/A) The events occurring in the mitochondrial matrix include the Tricarboxylic Acid $(TCA)$ cycle (Krebs cycle). The cycle begins with the condensation of an acetyl group $(2C)$ with oxaloacetic acid ($OAA$,$4C$) and water to yield citric acid $(6C)$,catalyzed by citrate synthase.
Following this,citric acid undergoes isomerization to isocitrate,followed by two successive steps of decarboxylation,forming $\alpha$-ketoglutaric acid and then succinyl-$CoA$.
Succinyl-$CoA$ is then oxidized to $OAA$ to complete the cycle. During this process,$GTP$ is synthesized via substrate-level phosphorylation,which is then converted to $ATP$. Additionally,$NAD^{+}$ is reduced to $NADH + H^{+}$ at three points,and $FAD^{+}$ is reduced to $FADH_{2}$ at one point.
The event occurring in the inner mitochondrial membrane is the Electron Transport System $(ETS)$. In this process,electrons from $NADH$ and $FADH_{2}$ (produced in the matrix) are passed through a series of complexes ($Complex-I$ to $IV$).
As electrons move through the $ETS$,protons $(H^{+})$ are pumped into the intermembrane space,creating a proton gradient. This gradient drives $ATP$ synthase $(Complex-V)$,which synthesizes $ATP$ from $ADP$ and inorganic phosphate $(Pi)$ as protons flow back into the matrix. Oxygen acts as the final electron acceptor,combining with electrons and protons to form water.