Respiration in Plants - TCA cycle and Electron transport system (aerobic)

The Link Reaction (Oxidative Decarboxylation of Pyruvate) occurs in the mitochondrial matrix where $Pyruvic \text{ } acid$ is converted to $Acetyl \text{ } CoA$ using the enzyme $Pyruvate \text{ } dehydrogenase$.

The TCA Cycle (Krebs Cycle) begins with the condensation of $Acetyl \text{ } CoA$ with $Oxaloacetic \text{ } acid \text{ } (OAA)$ to form $Citric \text{ } acid$.

In one turn of the TCA cycle, three molecules of $NAD^+$ are reduced to $NADH + H^+$, and one molecule of $FAD^+$ is reduced to $FADH_2$.

Substrate-level phosphorylation in the TCA cycle occurs during the conversion of $Succinyl \text{ } CoA$ to $Succinic \text{ } acid$, producing one molecule of $GTP$ (which is converted to $ATP$).

The Electron Transport System (ETS) is located on the inner mitochondrial membrane and consists of four complexes: Complex I ($NADH$ dehydrogenase), Complex II ($FADH_2$ dehydrogenase), Complex III (Cytochrome $bc_1$ complex), and Complex IV (Cytochrome $c$ oxidase).

Oxygen acts as the terminal electron acceptor and is reduced to form $H_2O$.

Oxidative Phosphorylation is the process of $ATP$ synthesis driven by the proton gradient across the inner mitochondrial membrane, facilitated by Complex V ($ATP$ synthase).

For every $NADH$ oxidized in the ETS, $3$ molecules of $ATP$ are produced, and for every $FADH_2$, $2$ molecules of $ATP$ are produced.