ATP (adenosine triphosphate) is the primary energy currency of cells. It is a molecule that stores and releases energy through the hydrolysis of its terminal phosphate bond.

Oxidative phosphorylation is the process by which cells generate ATP from glucose. It involves the transfer of electrons from NADH and FADH2 to oxygen through a series of electron carriers, resulting in the generation of a proton gradient across the inner mitochondrial membrane. This gradient is used to drive the synthesis of ATP by ATP synthase.

The electron transport chain is a series of protein complexes located in the inner mitochondrial membrane. It plays a crucial role in cellular respiration by transferring electrons from NADH and FADH2 to oxygen, generating a proton gradient across the membrane. This gradient is used to drive the synthesis of ATP by ATP synthase.

ATP synthase is an enzyme located in the inner mitochondrial membrane. It uses the proton gradient generated by the electron transport chain to drive the synthesis of ATP from ADP and inorganic phosphate.

Glycolysis is the first stage of cellular respiration. It is a series of ten enzymatic reactions that occur in the cytoplasm of cells and result in the breakdown of glucose into two molecules of pyruvate.

The Krebs cycle, also known as the citric acid cycle or the tricarboxylic acid cycle, is a series of nine enzymatic reactions that occur in the mitochondria of cells. It plays a crucial role in cellular respiration by generating ATP, NADH, and FADH2, and releasing carbon dioxide as a waste product.

NADH and FADH2 are electron carriers that play a crucial role in cellular respiration. They are generated during glycolysis and the Krebs cycle and are used to transfer electrons to the electron transport chain, where they are used to generate ATP.

Oxygen is the final electron acceptor in cellular respiration. It accepts electrons from the electron transport chain and combines with them to form water.

The overall efficiency of cellular respiration is approximately 25%. This means that only about 25% of the energy stored in glucose is converted into ATP during cellular respiration. The remaining energy is lost as heat.

Aerobic respiration requires oxygen, while anaerobic respiration does not. Aerobic respiration produces more ATP than anaerobic respiration. Aerobic respiration occurs in the mitochondria, while anaerobic respiration occurs in the cytoplasm.

Fermentation is a process that occurs in the absence of oxygen. It allows cells to regenerate NAD+ and FAD, which are necessary for glycolysis and the Krebs cycle to continue.

The two main types of fermentation are lactic acid fermentation and alcoholic fermentation. Lactic acid fermentation is carried out by some bacteria and muscle cells, and it results in the production of lactic acid. Alcoholic fermentation is carried out by yeast and some bacteria, and it results in the production of ethanol and carbon dioxide.

The proton gradient across the inner mitochondrial membrane is used to drive the synthesis of ATP by ATP synthase. As protons flow down the gradient, they pass through ATP synthase and cause it to change shape, which results in the synthesis of ATP.

The chemiosmotic hypothesis explains how ATP is synthesized, how protons are pumped across the inner mitochondrial membrane, and how electrons are transferred through the electron transport chain. It is a unifying theory that explains the overall process of cellular respiration.

Thermodynamics is used to explain the efficiency, direction, and equilibrium of cellular respiration. It provides a framework for understanding the energy transformations that occur during cellular respiration.